Construction method for combined shield tunneling of metro in anhydrous sand layer crossing existing line with micro-disturbance

Abstract

This invention discloses a method for micro-disturbance construction of a combined shield tunneling and cut-and-cover tunnel through an existing railway line in anhydrous sand layers, belonging to the field of subway construction technology. The method includes the following construction steps: S1, surveying and setting out and establishing a monitoring system; S2, end reinforcement and advance support operations; S3, shield launching and trial excavation operations; S4, shield tunneling construction; S5, cut-and-cover tunnel portal construction; S6, cut-and-cover tunnel sectional excavation and support; S7, connection construction to the existing railway line; S8, breakthrough surveying and shield receiving; S9, full-process monitoring and dynamic adjustment. This invention, through optimization measures targeting the characteristics of anhydrous sand layers, enables the construction method to better adapt to the complex geological conditions of anhydrous sand layers.

Description

Technical Field

[0001] This invention belongs to the field of subway construction technology, specifically relating to a method for micro-disturbance construction of subway shield tunneling combined with underground excavation through existing railway lines in waterless sand layers. Background Technology

[0002] With the acceleration of urbanization, the scale of urban rail transit construction is constantly expanding, and the densification of rail transit networks has become a development trend. Against this backdrop, there is an increasing number of new subway lines crossing existing operating lines. Among these, crossing projects under anhydrous sand layer geological conditions are particularly challenging. Anhydrous sand layers are characterized by poor self-stabilization and high particle flowability. Traditional construction methods have revealed many problems when dealing with such geological conditions. First, risk identification is incomplete. Due to insufficient understanding of the complex geological characteristics of anhydrous sand layers and their interaction mechanisms with existing lines, it is difficult to accurately identify all potential risks, such as the risk of localized collapse caused by sand layer seepage, posing hidden dangers to construction safety.

[0003] The tunneling parameters of the tunnel boring machine (TBM) failed to fully consider the characteristics of anhydrous sand layers, resulting in excessive disturbance to the strata during the tunneling process. For example, unreasonable settings for parameters such as advance speed and soil chamber pressure can easily cause excessive compression or loosening of the sand layer, leading to ground deformation. Traditional grouting methods are difficult to form an effective reinforcement system in anhydrous sand layers. The sand layer has large pores and loose particles, making it easy for grout to leak out and fail to fully fill the pores and cement the sand particles, resulting in the reinforced sand layer still not providing sufficient bearing capacity and stability. These problems make it extremely easy to cause ground disturbance when crossing existing lines in anhydrous sand layers, posing a serious threat to the normal operation of existing lines and failing to meet the high standards required for complex crossing projects in modern urban rail transit. A combined micro-disturbance construction method for tunnel boring machines (TBMs) in anhydrous sand layers is proposed to ensure the safe operation of existing lines and the smooth construction of new lines. Summary of the Invention

[0004] The purpose of this invention is to provide a method for micro-disturbance construction of subway shield tunneling combined with underground excavation through existing railway lines in waterless sand layers, so as to realize the micro-disturbance construction of subway shield tunneling combined with underground excavation through waterless sand layers.

[0005] To achieve the above objectives, embodiments of the present invention provide a method for micro-disturbance construction of a combined shield tunneling and underground excavation method for subway lines through anhydrous sand layers, comprising the following construction steps: S1. Surveying and setting out and monitoring system layout: Using total station and level instrument to survey the shield tunneling line, the outline of the cut-and-cover excavation, and the position of the gate, set up surface, pipeline, and building settlement observation points in the construction impact area, set up automated monitoring sections and install monitoring elements in the existing operating line, and collect and determine the initial monitoring values. S2. End reinforcement and advanced support operations: For the shield launching and receiving ends, plain piles combined with sleeve valve pipe grouting are used to reinforce the strata. For the tunnel excavation and before each cycle of excavation, advanced small guide pipes are installed in the arch and grouting is completed to form an advanced reinforcement ring outside the excavation outline. S3. Shield launching and trial excavation operations: install launching bracket and reaction frame, complete shield machine assembly and debugging and tunnel portal retaining structure demolition, and control shield machine to cut into the tunnel face to complete launching; S4. Shield tunneling construction: When the shield tunnel crosses over or sideways through existing lines and surrounding risk sources, it shall be continuously excavated at a uniform speed, and grouting operations shall be carried out simultaneously throughout the process to control the shield attitude and the single correction amplitude, and complete the shield tunneling section construction. S5. Construction of the tunnel gate: After the main structure of the shield receiving shaft is completed, double rows of advanced small guide pipes are installed along the outer contour of the tunnel gate and grouting is used for reinforcement. The retaining piles are broken in sequence by manual pneumatic picks. The grid steel frame is densely arranged at the tunnel entrance and the connecting bars are welded. The tunnel gate is supported and closed by spraying concrete. S6. The excavation and support of the cut-and-cover tunnel are carried out in stages according to the sectional excavation method. After each designed advance is excavated, the initial shotcrete, grid steel frame erection, steel mesh hanging, anchor pipe construction and re-shotcrete operation are completed immediately to make the initial support quickly closed into a ring. S7. Existing line connection construction: At the connection point between the tunnel section and the existing line, first set up brick partition walls and structural columns to complete physical isolation, use wire saw to cut the existing structure into sections and statically, and implement multiple waterproofing measures according to design requirements to complete the connection between the old and new structures. S8. Breakthrough Measurement and Shield Reception: Before the shield reaches the receiving shaft, multiple breakthrough measurements are completed according to the design mileage. The shield attitude is checked and adjusted. After entering the receiving reinforcement area, the tunneling parameters are adjusted to complete the tunneling of the receiving section. After the shield enters the receiving shaft, the segments at the tunnel entrance are immediately grouted and sealed. S9. Full-process monitoring and dynamic adjustment: Continuous monitoring of existing line structure deformation, surface settlement, pipeline settlement, and tunnel structure deformation throughout the construction process. Dynamic adjustment of construction parameters based on monitoring data. When the monitoring value reaches the early warning threshold, corresponding early warning response and disposal measures are initiated.

[0006] For example, in the micro-disturbance construction method for subway shield tunneling combined with underground excavation through existing lines in at least one embodiment of this disclosure, in step S1 of measurement and layout and monitoring system setup, the measurement deviation of the shield tunneling line is controlled within ±20mm, the measurement deviation of the underground excavation outline is controlled within ±10mm, and the position deviation of the monitoring point layout is ≤5mm; the automated monitoring elements within the existing line include a small prism and a static level.

[0007] For example, in at least one embodiment of the present disclosure, the method for micro-disturbance construction of a subway shield tunneling combined with existing railway line crossing in anhydrous sand layers includes step S2, end reinforcement, which uses two rows of Φ800@1200mm C20 plain concrete piles. Grouting is performed between the piles using sleeve valves. The reinforcement range is 3m vertically, horizontally, and vertically within the tunnel, and 3m longitudinally. After reinforcement, the unconfined compressive strength of the reinforced body is tested to be ≥0.5MPa, and the permeability coefficient is <1.0×10⁻⁶. -6 Only after the speed reaches cm / s can subsequent tunnel portal breaking operations be carried out.

[0008] For example, in the micro-disturbance construction method for combined tunneling and underground excavation of subway shield tunnels through existing lines in anhydrous sand layers provided by at least one embodiment of this disclosure, in step S2 of the advanced support operation, the advanced small guide pipes are welded steel pipes with a diameter of 32×3.25mm and a length of 2m, which are laid out within a 150° range of the arch, with an installation angle of 30° and a circumferential spacing of 300mm, and one ring is installed for each grid; Φ6~8mm overflow holes are drilled within 1m of the front end of the small guide pipes, and cement-water glass double liquid grout is used for grouting, with the grouting pressure controlled at 0.3~0.5MPa and the grout diffusion radius not less than 0.25m.

[0009] For example, in at least one embodiment of the present disclosure, the method for micro-disturbance construction of subway shield tunneling combined with underground excavation through existing lines in waterless sand layers includes step S2, in the shield launching and trial excavation operations, where the deviation between the center of the launching bracket and the tunnel design axis is controlled within ±10mm, and the end face of the reaction frame is perpendicular to the centerline of the bracket; the tunneling parameters during the shield launching stage are controlled as follows: soil chamber pressure 1.0~1.4bar, tunneling speed 5~10mm / min, cutterhead rotation speed 0.8~1.0rpm, and the installation and adjustment of the tunnel portal sealing device are completed simultaneously.

[0010] For example, in the micro-disturbance construction method for subway shield tunneling combined with underground excavation in waterless sand layers provided in at least one embodiment of this disclosure, in step S4 of the shield tunneling construction, parameters such as soil chamber pressure, tunneling speed, and synchronous grouting volume are continuously adjusted based on surface settlement monitoring data.

[0011] For example, in at least one embodiment of the present disclosure, the method for micro-disturbance construction of a subway shield tunneling combined with underground excavation in anhydrous sand layers is as follows: In step S4, during shield tunneling construction, when the shield tunneling passes through the existing line and risk source, the soil chamber pressure is stably controlled at 1.0~1.4 bar with a fluctuation range of ≤±0.2 bar, the tunneling speed is stably controlled at 40~50 mm / min, and the tunneling is maintained at a uniform speed and continuous passage. The amount of excavated soil is controlled by volume and weight, with the amount of excavated soil per ring controlled at 46.1±2 m³. The horizontal attitude of the shield is controlled within ±20 mm, the vertical attitude front point is controlled within ±20 mm, and the rear point is controlled within -30~-10 mm. The single correction amount does not exceed 4 mm / m.

[0012] For example, in at least one embodiment of the present disclosure, a method for micro-disturbance construction of a subway shield tunneling combined with underground excavation through an existing railway line in anhydrous sand layers is provided. In step S4, during shield tunneling construction, the grouting volume is increased to 1.2 times that of the ordinary section, 5.4 m³ / ring, and the grouting pressure is controlled at 2.0~4.0 bar. After the segments exit the shield tail, secondary grouting is performed. Secondary grouting is performed every 3 rings when crossing the risk source section, and the grouting pressure is ≤0.5 MPa. When passing under a power tunnel, deep hole grouting is performed through reserved grouting holes after the segments exit the shield tail, and the grouting pressure is controlled at 0.5~0.8 MPa to supplement and reinforce the soil below the risk source.

[0013] For example, in the micro-disturbance construction method for combined tunneling and excavation of subway shield tunnels through existing lines in waterless sand layers provided by at least one embodiment of this disclosure, in step S5 of the tunneling gate construction, the advance guide pipes are made of welded steel pipes with a diameter of 32×3.25mm and a length of 3.5m, arranged in a horizontal double-row quincunx pattern within a 150° range along the outer contour arch of the gate, with a circumferential spacing of 300mm and a grouting pressure of 0.3~0.5MPa; the retaining piles are removed manually using hand-held pneumatic picks, and the removal sequence is from top to bottom and from the center to both sides layer by layer. At the opening, three grid steel frames are densely arranged with a spacing of 300mm, and double-layer Φ20 connecting bars are arranged alternately inside and outside. 300mm thick C25 concrete is sprayed to complete the support and closure.

[0014] For example, in the micro-disturbance construction method for combined tunneling and unlined excavation of subway shield tunnels through existing lines in at least one embodiment of this disclosure, in step S6 of the tunnel excavation and support, the excavation method is adapted according to the tunnel cross-section size. Specifically, for 6.5m QA / QD type cross-sections, two pilot tunnels are excavated using the upper and lower bench method, with core soil reserved on the upper bench and the spacing between the upper and lower benches staggered by 5-10m; for 9.4m QC type cross-sections, four pilot tunnels are excavated using the CRD method, with each pilot tunnel staggered by 5-7m; and for 14.1m QB type cross-sections, nine pilot tunnels are excavated using the double-sidewall pilot tunnel method. Each pilot tunnel is constructed strictly according to the design sequence, with the excavation distance of the same numbered chambers on both sides staggered by 8-10m.

[0015] The significant technical effects of the embodiments of the present invention are as follows: The shield tunneling, including its launch, excavation, reception, and underground excavation, proceeded smoothly, improving overall construction efficiency. Simultaneously, by dynamically adjusting construction parameters, construction delays or rework due to unreasonable parameters were avoided, ensuring minimal disruption to existing lines during the construction of the new line. Detailed Implementation

[0016] The embodiments of the technical solution of this application will be described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are intended to cover non-exclusive inclusion.

[0018] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0019] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0020] In the description of the embodiments of this application, the term "and / or" is merely a description of the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship. In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple groups" refers to two or more groups (including two groups), and "multiple pieces" refers to two or more pieces (including two pieces).

[0021] In the description of the embodiments of this application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicate the orientation or positional relationship only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the embodiments of this application.

[0022] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation", "connection", "linking", and "fixing" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components.

[0023] A method for micro-disturbance construction of subway shield tunneling combined with underground excavation through existing railway lines in anhydrous sand layers according to one embodiment of the present invention includes the following construction steps: S1. Surveying and setting out and monitoring system layout: Using total station and level instrument to survey the shield tunneling line, the outline of the cut-and-cover excavation, and the position of the gate, set up surface, pipeline, and building settlement observation points in the construction impact area, set up automated monitoring sections and install monitoring elements in the existing operating line, and collect and determine the initial monitoring values. S2. End reinforcement and advanced support operations: For the shield launching and receiving ends, plain piles combined with sleeve valve pipe grouting are used to reinforce the strata. For the tunnel excavation and before each cycle of excavation, advanced small guide pipes are installed in the arch and grouting is completed to form an advanced reinforcement ring outside the excavation outline. S3. Shield launching and trial excavation operations: install launching bracket and reaction frame, complete shield machine assembly and debugging and tunnel portal retaining structure demolition, and control shield machine to cut into the tunnel face to complete launching; S4. Shield tunneling construction: When the shield tunnel crosses over or sideways through existing lines and surrounding risk sources, it shall be continuously excavated at a uniform speed, and grouting operations shall be carried out simultaneously throughout the process to control the shield attitude and the single correction amplitude, and complete the shield tunneling section construction. S5. Construction of the tunnel gate: After the main structure of the shield receiving shaft is completed, double rows of advanced small guide pipes are installed along the outer contour of the tunnel gate and grouting is used for reinforcement. The retaining piles are broken in sequence by manual pneumatic picks. The grid steel frame is densely arranged at the tunnel entrance and the connecting bars are welded. The tunnel gate is supported and closed by spraying concrete. S6. The excavation and support of the cut-and-cover tunnel are carried out in stages according to the sectional excavation method. After each designed advance is excavated, the initial shotcrete, grid steel frame erection, steel mesh hanging, anchor pipe construction and re-shotcrete operation are completed immediately to make the initial support quickly closed into a ring. S7. Existing line connection construction: At the connection point between the tunnel section and the existing line, first set up brick partition walls and structural columns to complete physical isolation, use wire saw to cut the existing structure into sections and statically, and implement multiple waterproofing measures according to design requirements to complete the connection between the old and new structures. S8. Breakthrough Measurement and Shield Reception: Before the shield reaches the receiving shaft, multiple breakthrough measurements are completed according to the design mileage. The shield attitude is checked and adjusted. After entering the receiving reinforcement area, the tunneling parameters are adjusted to complete the tunneling of the receiving section. After the shield enters the receiving shaft, the segments at the tunnel entrance are immediately grouted and sealed. S9. Full-process monitoring and dynamic adjustment: Continuous monitoring of existing line structure deformation, surface settlement, pipeline settlement, and tunnel structure deformation throughout the construction process. Dynamic adjustment of construction parameters based on monitoring data. When the monitoring value reaches the early warning threshold, corresponding early warning response and disposal measures are initiated.

[0024] The optimized implementation of measures such as end reinforcement, advanced support, and waterproofing at existing line connections improved the effectiveness of ground reinforcement and waterproofing. New grouting materials and processes ensured the formation of an effective reinforcement system in the anhydrous sand layer, enhancing its bearing capacity and stability. Multiple waterproofing measures guaranteed the waterproofing quality at the junctions of new and old structures, reducing the risk of leakage and extending the service life of the tunnel structure. The orderly execution of each stage of shield tunneling—from launch and excavation to receiving and cut-and-cover construction—improved overall construction efficiency. Furthermore, dynamic adjustment of construction parameters avoided construction stoppages or rework due to unreasonable parameters, further ensuring the construction progress.

[0025] Optimization measures targeting the characteristics of anhydrous sand layers enable construction methods to better adapt to the complex geological conditions of these layers. Simultaneously, these measures ensure smooth construction under various environmental conditions, minimizing the impact on the surrounding environment. Detailed monitoring and dynamic adjustments throughout the entire process, along with close collaboration with existing line operation and management departments, minimized disruption to the normal operation of existing lines while ensuring their operational safety, achieving a harmonious coexistence between new line construction and existing line operation.

[0026] In some examples, in step S1, the measurement deviation of the tunnel boring line is controlled within ±20mm, the measurement deviation of the cut-and-cover excavation outline is controlled within ±10mm, and the position deviation of the monitoring points is ≤5mm; the automated monitoring elements within the existing line include small prisms and static levels.

[0027] For example, a high-precision total station, such as the Leica TS16 total station, can be selected. Its angle measurement accuracy can reach ±1″ and its distance measurement accuracy is ±(1mm + 1ppm × D), which can meet the requirements of high-precision measurement.

[0028] Based on the coordinate data of the tunnel boring machine (TBM) excavation route provided in the design drawings, surveying was conducted on the ground at the construction site. First, a benchmark point was established near the TBM launch shaft. This benchmark point should be located in a stable location unaffected by construction. Its precise coordinates were determined by connecting it to the urban surveying and control network. Then, starting from the benchmark point, control points were established every 5 meters along the design route. During the surveying process, to ensure measurement accuracy, the total station was strictly leveled and centered. For each control point, multiple measurements were taken and the average value was calculated, typically three times. The horizontal and vertical angle deviations were controlled within ±3″, and the distance measurement deviation within ±3mm, ultimately ensuring that the TBM excavation route measurement deviation was controlled within ±20mm. For example, in a certain measurement, the three measurements of a control point were: the first measurement coordinates were (X1, Y1), the second (X2, Y2), and the third (X3, Y3). After calculating the average, the final coordinates (X, Y) were obtained. Comparing this with the design coordinates, the deviation was within the allowable range.

[0029] The established control points were fixed to the ground using steel nails, and reinforced with concrete around the nails to prevent displacement. At the same time, clearly marked signs were placed near the control points, indicating their numbers, coordinates, and other information for easy reference during subsequent construction surveying.

[0030] A level instrument and a steel tape were used to measure the outline of the underground excavation. The level instrument selected was a Trimble Dini03 electronic level with a high accuracy, and its mean square error for the elevation difference measurement per kilometer was ±0.3mm. The steel tape used was a 50m steel tape that had passed metrological verification.

[0031] Based on the designed dimensions of the cut-and-cover tunnel, measurements are marked on the ground and retaining structure at the construction site. First, the design elevation of the tunnel is measured using a level, and the corresponding elevation points are marked on the retaining structure. Then, starting from the elevation points, a steel tape measure is used to measure the designed excavation outline dimensions, marking the outline position on the retaining structure every 1 meter. To ensure measurement accuracy, the steel tape should be kept horizontal and under uniform tension, controlled near the standard tension during tape calibration, with a deviation not exceeding ±5N. Simultaneously, when measuring elevation with the level, each reading should be taken twice, with the difference between the two readings controlled within ±1mm. Through these operations, the measurement deviation of the cut-and-cover excavation outline is controlled within ±10mm. For example, in the measurement of a certain section of the cut-and-cover tunnel, after measuring a certain elevation point with a level, the outline position is measured using a steel tape measure, and multiple measurements are compared to ensure that the deviation at each point is within the allowable range.

[0032] After marking the outline, the entire outline is checked and verified. A total station is used to measure the coordinates of key points on the outline, and these coordinates are compared with the design coordinates, with deviations controlled within ±10mm. If any deviation exceeds the allowable range, the cause is promptly identified and adjustments are made.

[0033] Settlement observation points were set up on the ground surface in the construction impact area at 5-meter intervals. Observation stakes were installed by drilling holes in the ground. The stakes were made of 32mm diameter steel bars, 800mm long, and hemispherical at the top. The drill holes were 50mm in diameter and 600mm deep. After the stakes were inserted, they were fixed with cement mortar. After installation, the elevation was measured using a level as the initial value. To ensure accurate stake placement, a total station was used for positioning during installation, ensuring a deviation of ≤5mm. For example, when installing surface settlement observation points in a certain area, the actual position of the stake was controlled within 3mm of the designed position using a total station.

[0034] For underground pipelines within the construction impact area, observation points will be fixed to the pipelines using either clamps or welding, depending on the pipeline type and burial depth. For metal pipelines, welding is preferred, where observation points are welded to the pipeline, taking care to avoid damage during welding. For non-metallic pipelines, clamps are used to fix the observation points to the pipeline; the clamps should be securely installed to prevent loosening. The observation points will be specially made stainless steel observation markers with a flat top for easy leveling. During the deployment process, a total station will be used to measure the location of the observation points, ensuring that the positional deviation is ≤5mm.

[0035] Observation markers are set up at key locations such as the corners of walls and column bases of surrounding buildings. For masonry structures, expansion bolts are embedded by drilling holes in the corners, with the tops of the bolts machined into flat surfaces to serve as observation points. For concrete structures, stainless steel observation markers can be directly affixed to the surface of the column bases. Similarly, a total station is used to measure and locate the observation points, ensuring that the positional deviation is ≤5mm. For example, when setting up observation points at the corners of a building, the positional deviation was only 2mm using a total station.

[0036] On the track slabs, ballast, and other structures of the existing railway line's automated monitoring sections, the installation locations of small prisms are determined according to the monitoring plan. Generally, a small prism is installed every 5 meters, and the installation location should be chosen in a place that is convenient for total station measurements and not easily affected by construction interference.

[0037] The small prism is fixed to the structure using a dedicated small prism mounting bracket. The bracket is made of stainless steel, offering excellent stability and corrosion resistance. First, drill holes in the structure's surface, then secure the bracket to the structure using expansion bolts. Tighten the bolts to ensure the bracket is secure and reliable. Install the small prism on the bracket and adjust its angle so that its reflecting surface is perpendicular to the total station's line of sight. During installation, use the total station to measure the small prism's position, ensuring the positional deviation is ≤5mm. For example, when installing a small prism at a monitoring section, monitor the installation position in real-time using the total station to ensure the actual installation position deviates from the design position by less than 4mm.

[0038] After installation, install protective devices, such as protective boxes or guardrails, around the small prism to prevent it from being damaged by impact. Also, regularly inspect the small prism to ensure its position and angle have not changed.

[0039] Choose a relatively stable location within the existing railway line to install the static level, such as on an embedded part in the tunnel sidewall or on a stable foundation below the track slab. The installation location should be protected from factors such as vibration and excessive temperature changes to ensure the accuracy of the measurement data.

[0040] The base of the hydrostatic level is fixed to the embedded parts or foundation using bolts or welding, ensuring the base is level and secure. Then, the main body of the hydrostatic level is installed on the base and precisely leveled. A spirit level is used to check that the bubble of the hydrostatic level is centered, with a deviation controlled within ±0.5mm. Next, the inlet and outlet pipes of the hydrostatic level are connected, ensuring a tight connection and no leakage. During installation, a total station is used to measure the position of the hydrostatic level, ensuring that the positional deviation of its points is ≤5mm. For example, in one hydrostatic level installation, the positional deviation was controlled within 3mm using a total station.

[0041] Connect the hydrostatic level to the data acquisition system via a data cable and perform debugging. Check whether the data acquisition system can accurately acquire the measurement data from the hydrostatic level. Calibrate and verify the measurement data to ensure its accuracy and reliability. Simultaneously, set the data acquisition frequency and storage method for subsequent analysis and processing of the monitoring data.

[0042] In some examples, during the end reinforcement work in step S2, two rows of Φ800@1200mm C20 plain concrete piles were used, with sleeve valve grouting between the piles. The reinforcement range was 3m on each side of the tunnel, both vertically and horizontally, and 3m in length. After reinforcement, the unconfined compressive strength of the reinforced body was tested to be ≥0.5MPa and the permeability coefficient was <1.0×10⁻⁶. -6The speed must reach cm / s before subsequent tunnel portal demolition work can proceed. In step S2, the advanced support operation, the advanced small guide pipes are Φ32×3.25mm welded steel pipes with a length of 2m, which are laid within a 150° range of the arch, with an installation angle of 30° and a circumferential spacing of 300mm. One ring is installed for each grid. Φ6~8mm overflow holes are drilled within 1m of the front end of the small guide pipes. Cement-water glass double-liquid grout is used for grouting, and the grouting pressure is controlled at 0.3~0.5MPa. The grout diffusion radius is not less than 0.25m.

[0043] For example, depending on the geological conditions, the initial drilling speed should be controlled at 0.3-0.5 m / min. As the drilling depth increases, the drilling speed should be adjusted appropriately, generally not exceeding 1 m / min. During drilling, the operation of the drilling rig and changes in the geological formation should be closely observed. If any abnormality is found, drilling should be stopped immediately, the cause analyzed, and corresponding measures taken. For example, when encountering hard sand layers or obstacles, the drilling speed can be appropriately reduced and the drilling pressure increased to ensure smooth drilling.

[0044] Prepare high-quality drilling mud with a specific gravity controlled at 1.1-1.3 g / cm³ and a viscosity of 18-22 s. During drilling, the mud serves to protect the borehole wall and remove slag. It is injected into the borehole using a mud pump, forming a mud cake on the borehole wall to prevent collapse.

[0045] Although plain piles do not have a reinforcing cage, to ensure the integrity and stability of the pile body, similar operational points to those used when lowering a reinforcing cage can be adopted during concrete pouring. These include controlling the pouring speed and height of the concrete to prevent segregation.

[0046] Before pouring concrete, the drilling depth, diameter, and verticality are checked again to ensure they meet design requirements. Simultaneously, the slump of the concrete is tested and controlled between 180-220 mm to ensure workability and fluidity.

[0047] Underwater concrete pouring is performed using the tremie pipe method. The tremie pipe has a diameter of 250mm, and the bottom of the tremie pipe is positioned 30-50cm from the bottom of the borehole. Concrete pouring should be continuous and uninterrupted. At the start of pouring, the initial volume of concrete should ensure that the tremie pipe is embedded at least 1m into the concrete. During the pouring process, the embedment depth of the tremie pipe is strictly controlled, generally maintained between 2-6m, and the lifting height of the tremie pipe is adjusted by measuring the height of the concrete surface.

[0048] Two rows of C20 plain concrete piles with diameters of 800mm x 1200mm were installed. At the construction site, a total station was used to accurately measure and locate the pile positions, with the deviation of each pile position controlled within ±50mm. After the pile positions were determined, they were marked with lime or wooden stakes to facilitate subsequent construction.

[0049] A PVC pipe with an inner diameter of 50mm was selected as the sleeve valve pipe. An overflow hole was drilled every 30cm on the pipe body, with 4 overflow holes in each group and a hole diameter of 8mm. A one-way rubber valve was installed at the overflow hole to prevent slurry backflow.

[0050] After the plain pile construction is completed, a geological drilling rig is used to drill pilot holes between the piles. The pilot holes have a diameter of 100mm and a depth 0.5m deeper than the plain piles. After the pilot holes are completed, the fabricated sleeve valve pipe is inserted into the hole, with the top of the sleeve valve pipe extending 20cm above the ground for connection to the grouting equipment. After the sleeve valve pipe is inserted, cement mortar is filled between the pipe and the hole wall, ensuring a dense and secure fit.

[0051] The grouting uses a cement-water glass two-component grout. The grout is prepared with a cement-water-cement ratio of 1:1 and a water-glass-cement volume ratio of 1:1 to 1:0.5. First, the cement and water are mixed evenly according to the ratio to make cement grout. Then, the water glass is slowly added to the cement grout while stirring to ensure that the grout is mixed evenly.

[0052] The grouting pressure should be controlled between 0.5 and 1.0 MPa, and adjusted according to the geological conditions and grouting effect. The grouting speed is generally controlled at 20-30 L / min. During the grouting process, the changes in grouting pressure and grouting volume should be closely observed. If a sudden increase or decrease in grouting pressure or a sudden increase or decrease in grouting volume is found, grouting should be stopped immediately, the cause analyzed, and corresponding measures taken.

[0053] A segmented grouting method is adopted, with grouting proceeding from bottom to top, and each segment having a length of 1m. During the grouting process, adjacent sleeve valve pipes should be grouted at intervals to prevent cross-flow of grout.

[0054] The reinforcement area extends 3 meters vertically, horizontally, and longitudinally from the tunnel. During construction, the reinforcement area is precisely determined through surveying and setting out, and the reinforcement boundaries are marked on the ground using lime or wooden stakes. During grouting, the diffusion of the grout is closely monitored to ensure uniform diffusion within the reinforcement area, achieving the desired reinforcement effect.

[0055] After grouting is completed, core samples are drilled and specimens are prepared in the reinforced area according to specifications. The core sample diameter is 100 mm, and the height is twice the diameter. Three specimens are prepared for each group, and multiple groups of specimens are prepared in total, which are then tested at different ages.

[0056] The unconfined compressive strength of the specimens was tested using a compression testing machine. During the test, the loading rate was controlled between 0.5 and 1.0 MPa / min. The load at specimen failure was recorded, and the unconfined compressive strength was calculated. The test results showed that the unconfined compressive strength of the reinforced specimen was ≥0.5 MPa, meeting the design requirements.

[0057] The permeability coefficient of the reinforced body was determined using a constant head permeability test. Representative locations within the reinforced area were selected, and core samples were drilled to prepare permeability test specimens. The specimens had a diameter of 61.8 mm and a height of 40 mm.

[0058] The specimen was mounted on a permeameter, a certain water head pressure was applied, and the amount of water passing through the specimen within a certain time was measured. The permeability coefficient was calculated according to Darcy's law. The test results showed that the permeability coefficient of the solidified material was <1.0×10⁻⁶. -6 The speed is cm / s, which meets the design standards. Subsequent tunnel opening removal work can only proceed after the reinforcement effect has passed the inspection.

[0059] The advanced conduit uses welded steel pipes with a diameter of 32×3.25mm and a length of 2m, ensuring that the material and specifications of the steel pipes meet the design requirements. A visual inspection of the steel pipes is conducted, requiring that the surface of the steel pipes be free of cracks, obvious rust, and other defects.

[0060] Drill overflow holes with a diameter of 6-8mm within 1m of the tip of the small guide pipe, with a hole spacing of 10cm, arranged in a quincunx pattern. Use a bench drill or electric drill for drilling to ensure accurate hole positioning and that the hole diameter meets requirements. After drilling, clean the iron filings inside the small guide pipe to prevent clogging of the overflow holes.

[0061] Pre-installed small guide pipes were laid within a 150° range of the tunnel arch. Total station and level were used for precise measurement and positioning to determine the installation location and angle of the small guide pipes. The installation angle was 30°, and angle control lines were set on the tunnel face to ensure accuracy. During installation, a geological compass or inclinometer was used to monitor the angle of the small guide pipes in real time, with deviations controlled within ±2°.

[0062] The circumferential spacing of the small guide pipes is 300mm. The placement positions of the small guide pipes are marked on the working face with red paint or white lime according to the design spacing. During installation, construction must strictly follow the marked positions to ensure uniform circumferential spacing of the small guide pipes, with deviations controlled within ±20mm. One ring of small guide pipes is installed for each grid section to ensure the continuity and effectiveness of the pre-support.

[0063] Prepare the slurry according to the designed mix proportions. The water-cement ratio of the cement slurry is 1:1, and the volume ratio of water glass to cement slurry is 1:0.8. First, mix the cement and water evenly to make cement slurry. Then, slowly add the water glass to the cement slurry and stir evenly to make a cement-water glass two-component slurry.

[0064] The grouting pressure is controlled between 0.3 and 0.5 MPa and monitored in real time using a pressure gauge on the grouting pump. During the grouting process, the grouting pressure is adjusted appropriately according to the geological conditions and grouting effect. For example, in areas with loose sand layers, the grouting pressure can be appropriately increased to ensure that the grout can spread fully.

[0065] To ensure the grout diffusion radius is not less than 0.25m, the grouting volume and time are preliminarily determined based on geological conditions and experience before grouting. During grouting, changes in the working face and surrounding soil are observed, and observation points are set up around the grouting holes to measure the grout diffusion range. Grouting parameters are adjusted promptly to ensure the grout diffusion radius meets the requirements. For example, if the grout diffusion radius is found to be small, the grouting time can be appropriately extended or the grouting pressure increased.

[0066] By installing two rows of C20 plain concrete piles with diameters of 800mm and 1200mm, the piles penetrate deep into the ground, forming a robust supporting framework within the soil. The piles themselves possess high strength and rigidity, capable of withstanding the pressure of the soil above and effectively preventing vertical deformation and collapse. Grouting is then performed between the piles using sleeve valves. The grout fills the gaps between the piles, binding loose soil particles together, increasing the soil's cohesion and friction, and enhancing the overall stability of the strata. This provides a stable foundation for subsequent portal breaching, shield launching, and receiving operations.

[0067] The reinforcement area extends 3 meters vertically, horizontally, and vertically, and 3 meters longitudinally, forming a closed reinforcement zone around the tunnel end. This comprehensive reinforcement of the surrounding strata at the tunnel end prevents accidents such as collapses caused by local strata instability and ensures construction safety.

[0068] After reinforcement, the unconfined compressive strength of the reinforcement body is tested to be ≥0.5MPa. This ensures that the reinforcement body has sufficient strength to withstand the thrust of the tunnel boring machine (TBM) during launch and reception, soil pressure, and various loads during subsequent construction, preventing structural damage due to insufficient reinforcement body strength. For example, during TBM launch, the reinforcement body can stably transmit the thrust of the TBM, ensuring that the TBM can smoothly cut into the ground.

[0069] Permeability coefficient <1.0×10 -6The cm / s indicates that the solidified material has good seepage prevention performance. In the anhydrous sand layer, it effectively prevents the infiltration of groundwater, prevents the sand particles from being carried away by the flow of groundwater, and thus avoids problems such as sand layer cavities and collapse, maintaining the stable structure of the strata. At the same time, it also reduces the adverse effects of groundwater on construction, such as reducing the risk of water and sand inrush during the tunnel portal breach.

[0070] Only after all indicators of the reinforced soil meet the standards can subsequent tunnel portal removal operations be carried out. This ensures the stability of the strata during the tunnel portal removal process, reduces the probability of safety accidents such as collapse and sand inrush at the tunnel portal, protects the safety of construction personnel and the smooth advancement of equipment such as tunnel boring machines, and lays the foundation for the safe and smooth progress of the entire tunnel construction.

[0071] Pre-installed small guide pipes are laid out within a 150° range of the arch, with a circumferential spacing of 300mm. One ring is installed in each grid, forming a densely packed pre-support system. Φ6-8mm overflow holes are drilled within 1m of the front end of the small guide pipes. After grouting, the grout diffuses into the surrounding soil through the overflow holes, tightly bonding the small guide pipes with the surrounding soil to form an arch-like reinforced area. This provides excellent support for the arch soil, effectively constraining deformation during excavation, ensuring the accuracy of the excavation profile, preventing over-excavation or under-excavation, and providing favorable conditions for subsequent initial support construction.

[0072] The small guide pipe uses Φ32×3.25mm welded steel pipes with a length of 2m, possessing certain strength and rigidity, and can provide preliminary support to the soil before grouting. Grouting uses a cement-water glass dual-liquid grout, which features rapid setting speed and high early strength. After grouting, the grout diffuses in the soil, filling soil pores and binding loose soil particles together, thus improving the soil's strength and bearing capacity. Especially in strata with poor self-stability, such as anhydrous sand layers, pre-support significantly enhances the stability of the soil ahead of the excavation face, enabling the soil to better withstand the disturbances brought about by tunnel excavation and reducing the possibility of soil collapse.

[0073] The grouting pressure is controlled at 0.3-0.5 MPa. Through reasonable pressure control, the grout can be evenly diffused in the soil. This ensures that the grout will not fail to fill the soil pores due to insufficient pressure, while avoiding excessive pressure that could lead to uncontrolled grout diffusion, unnecessary waste, or adverse effects on the surrounding environment.

[0074] The requirement that the grout diffusion radius be no less than 0.25m ensures that the soil between adjacent small guide pipes is adequately reinforced, forming a continuous and stable reinforcement zone, thus improving the overall effectiveness of the pre-support. Precise control of grouting parameters effectively improves the reliability of the pre-support, guaranteeing the safety and quality of the cut-and-cover tunnel construction.

[0075] In some examples, during step S2, the shield launching and trial excavation operations, the deviation between the center of the launching bracket and the tunnel design axis is controlled within ±10mm, and the end face of the reaction frame is perpendicular to the centerline of the bracket; the tunneling parameters during the shield launching stage are controlled as follows: soil chamber pressure 1.0~1.4bar, tunneling speed 5~10mm / min, cutterhead speed 0.8~1.0rpm, and the installation and adjustment of the tunnel portal sealing device are completed simultaneously.

[0076] For example, the height, slope, and levelness are adjusted using the adjusting bolts and jacks at the bottom. A total station is used to monitor the deviation between the bracket center and the tunnel's design axis in real time. By fine-tuning the bracket position, the deviation is controlled within ±10mm. For instance, if the deviation is found to be +8mm, the bracket is slowly pushed towards the design axis using jacks until the deviation meets the requirements.

[0077] The bracket is securely connected to the bottom plate of the launching shaft using pre-embedded steel plates and high-strength bolts. The bolt tightening torque meets the design requirements to ensure that the bracket will not shift during the shield launching process.

[0078] Embedded parts are installed on the rear wall of the shield tunneling shaft, according to the dimensions and design requirements of the reaction frame. The position and size accuracy of the embedded parts are controlled within ±5mm to ensure accurate installation of the reaction frame.

[0079] By adjusting the position and angle of the reaction frame, the end face of the reaction frame is made perpendicular to the centerline of the bracket, with the perpendicularity deviation controlled within ±2mm / m. For example, if the measurement shows that the perpendicularity deviation between the end face of the reaction frame and the centerline of the bracket is +3mm / m, the reaction frame is finely adjusted by adjusting the support device at the bottom of the reaction frame until the perpendicularity meets the requirements.

[0080] After the reaction frame is installed, check its perpendicularity to the centerline of the support frame and the firmness of each connection to ensure that the reaction frame can withstand the thrust of the tunnel boring machine when the tunnel boring machine starts to run.

[0081] Based on the geological conditions of the anhydrous sand layer, the tunnel depth, and the results of previous geological surveys and numerical simulations, the soil chamber pressure during the initial shield tunneling stage was determined to be between 1.0 and 1.4 bar. For example, when the tunnel depth is 15m and the unit weight of the anhydrous sand layer is 18kN / m³, the initial soil chamber pressure setting value was determined to be 1.2 bar through theoretical calculations and empirical formulas.

[0082] During the tunnel boring machine's (TBM) initiation process, the soil pressure in the soil chamber is monitored in real time using a soil chamber pressure sensor. When the soil pressure in the soil chamber falls below a set value (e.g., 1.0 bar), the TBM control system automatically increases the excavation speed of the screw conveyor and appropriately increases the thrust of the propulsion cylinders, gradually raising the soil pressure in the soil chamber back to the set range.

[0083] If the soil chamber pressure is higher than the set value (e.g., 1.4 bar), reduce the discharge speed of the screw conveyor and decrease the thrust of the propulsion cylinder to lower the soil chamber pressure. For example, when the soil chamber pressure monitoring value is 1.5 bar, increase the discharge speed of the screw conveyor from 20 m³ / h to 25 m³ / h, while simultaneously reducing the thrust of the propulsion cylinder from 15000 kN to 13000 kN, so that the soil chamber pressure gradually returns to the set range.

[0084] Considering the equipment debugging, geological adaptability, and impact on existing lines during the initial shield tunneling phase, the tunneling speed will be controlled at 5-10 mm / min. Initially, due to the need for equipment break-in, the tunneling speed will be set at 5 mm / min. As the shield machine's systems gradually stabilize and a more accurate understanding of the geological conditions is achieved, the tunneling speed can be appropriately increased to 8-10 mm / min.

[0085] The tunneling speed is controlled by the tunnel boring machine's propulsion system. Operators adjust the stroke speed of the propulsion cylinders on the machine's control panel based on the machine's operating status, soil pressure, and ground feedback. For example, if the soil pressure is too high and the ground is relatively stable, the propulsion cylinder stroke speed can be appropriately increased, raising the tunneling speed from 5 mm / min to 8 mm / min. If sudden changes in ground conditions or equipment malfunctions, the propulsion cylinder stroke speed should be immediately reduced to 3-5 mm / min to ensure safe tunneling.

[0086] Based on the particle characteristics of the anhydrous sand layer, the cutterhead configuration of the tunnel boring machine (TBM), and the required tunneling parameters, the cutterhead rotation speed was determined to be controlled between 0.8 and 1.0 rpm. For anhydrous sand layers with finer particles and lower hardness, the cutterhead rotation speed can be set to 0.8 rpm to ensure that the cutters can effectively cut the soil while avoiding excessive wear due to excessive rotation speed. For sand layers with coarser particles and higher hardness, the cutterhead rotation speed can be appropriately increased to 1.0 rpm to enhance the cutting ability of the cutters.

[0087] The cutterhead rotation speed is controlled by the cutterhead drive system of the tunnel boring machine (TBM). During the initial tunneling process, operators adjust the frequency of the cutterhead drive motor on the control panel according to the geological conditions and tunneling progress, thereby changing the cutterhead rotation speed. For example, when the TBM tunnels into an area where the sand particles become coarser, the frequency of the cutterhead drive motor is increased from 40Hz to 50Hz, increasing the cutterhead rotation speed from 0.8rpm to 1.0rpm, ensuring that the cutters can smoothly cut the soil and improve tunneling efficiency.

[0088] Before the tunnel boring machine (TBM) starts operation, the sealing effect of the tunnel portal sealing device is checked. Water is injected into the sealing device to observe for any leaks. If a small leak is found, the location is marked for adjustment.

[0089] The deviation between the center of the launching bracket and the tunnel's design axis is controlled within ±10mm, ensuring that the tunnel boring machine (TBM) can advance along the design axis during launch. This avoids poor launching posture of the TBM due to excessive bracket position deviation, which could affect the accuracy of subsequent excavation and the quality of tunnel formation. The reaction frame end face is perpendicular to the centerline of the bracket, ensuring uniform thrust transmission during launching and preventing uneven force distribution, offset, or torsion caused by a non-perpendicular reaction frame. This lays the foundation for a smooth launching and stable subsequent excavation of the TBM.

[0090] Precisely installed launching brackets and reaction frames provide stable support and reaction force for the tunnel boring machine (TBM), withstanding the enormous thrust during launching and ensuring the safety and stability of the launching process. This avoids safety accidents caused by improper installation of the brackets and reaction frames, such as bracket displacement or reaction frame deformation, thus ensuring the safety of construction personnel and equipment.

[0091] By appropriately controlling the soil chamber pressure between 1.0 and 1.4 bar, the pressure within the chamber is kept in balance with the water and soil pressure of the anhydrous sand layer. This effectively prevents problems such as collapse and sand inrush caused by pressure imbalance in the anhydrous sand layer, maintains the stability of the strata, and protects the safety of the existing railway line. For example, during the initial tunnel boring machine (TBM) launch, accurate soil chamber pressure control avoids disturbance to the sand layer beneath the existing railway line, ensuring that the existing railway structure remains unaffected.

[0092] The tunneling speed was controlled at 5-10 mm / min, achieving efficient tunneling while ensuring the stable operation of all systems of the tunnel boring machine and the stability of the strata. This avoided the problems of excessive ground disturbance caused by excessively fast tunneling speed and the impact on construction progress caused by excessively slow tunneling speed. At the same time, the cutterhead rotation speed was controlled at 0.8-1.0 rpm, allowing the cutters to match the characteristics of the anhydrous sand layer, effectively cutting the soil, improving tunneling efficiency, and ensuring the smoothness and forming quality of the tunnel excavation face.

[0093] By rationally adjusting the tunneling parameters, the various components of the tunnel boring machine (TBM) operate within a reasonable range of conditions during the initial stage, reducing equipment wear. For example, proper matching of cutterhead speed and tunneling speed avoids abnormal wear caused by excessive or insufficient cutting of the cutters, extending their service life and reducing equipment maintenance costs.

[0094] A good tunnel portal sealing device can effectively prevent soil and water loss at the tunnel portal during the tunnel boring machine's launch, and prevent sand and groundwater from seeping out of the portal from the dry sand layer, thus polluting the construction site and the surrounding environment. For example, during the tunnel boring machine's launch process, the portal sealing device prevents sand and groundwater from contaminating the equipment and tracks inside the launch shaft, ensuring the cleanliness of the construction site.

[0095] A well-sealed tunnel portal system ensures the normal tunneling operation of the tunnel boring machine (TBM). It prevents pressure leakage in the tunnel chamber due to poor sealing, ensuring stable pressure and allowing the TBM to advance according to the set tunneling parameters. Simultaneously, it prevents damage to the TBM equipment from water or sand inrush at the tunnel portal, guaranteeing its safe operation.

[0096] In some examples, during the shield tunneling construction in step S4, parameters such as soil chamber pressure, tunneling speed, and synchronous grouting volume are continuously adjusted based on surface settlement monitoring data to establish a quantitative correlation between each parameter and stratum deformation, and to determine the optimal parameter combination for the shield tunneling risk source.

[0097] The soil pressure is adjusted according to the following formula: ; ; Where P is the setpoint for the soil chamber pressure, P0 is the baseline value for the soil chamber pressure, determined during the trial excavation section, typically 1.0~1.4 bar, and k p S is the soil pressure adjustment coefficient, which is taken as 0.2 here. 瞬 S represents the instantaneous settlement value of the tunnel centerline when the shield tunnel face passes through. 预 The pre-settlement value of the ground surface within a range of 3 times the excavation diameter of the shield tunnel in front of the tunnel face.

[0098] The tunneling speed is adjusted according to the following formula: ; Where v is the tunneling speed, v0 is the reference value of the tunneling speed, the optimal value calibrated in the test tunneling section, 40~50mm / min in the crossing section, and 5~10mm / min in the test tunneling section, k v Here, is the tunneling speed adjustment factor, taken as 0.3; i is the uneven surface settlement gradient of the shield tunnel section, ΔS. 停 S represents the additional settlement value resulting from a single shutdown; 警 The settlement warning threshold is set at 2.4 mm for crossing existing lines and 1.6 mm for existing line structure settlement. σ S S represents the standard deviation of surface subsidence fluctuation in the same segment. 控 The benchmark value for surface settlement control is 3mm for crossing existing lines and 2mm for the settlement of existing line structures.

[0099] The tunneling speed is adjusted according to the following formula:

[0100] Where Q is the synchronous grouting volume, Q0 is the baseline value of the synchronous grouting volume, the optimal value calibrated in the trial excavation section, the baseline being 1.65 times the theoretical building void, kq is the grouting volume adjustment coefficient, which is taken as 0.25 here, S 终 B represents the final surface settlement within a range of 3 times the shield excavation diameter after the shield tail passes, B is the measured settlement trough width coefficient, and B0 is the theoretical settlement trough width benchmark value. B0 = h·tan(45°) φ / 2), h is the tunnel depth, φ is the internal friction angle of the sand layer, △S 残 The value represents the residual settlement 24 hours after the shield tail passes through.

[0101] During the tunnel boring machine (TBM) tunneling operation, data such as soil pressure, tunneling speed, synchronous grouting volume, and corresponding surface settlement and stratum deformation are continuously recorded. For example, the values ​​of each parameter and the corresponding settlement data are recorded at regular time intervals (e.g., every 5 minutes). Data analysis software is used to organize and analyze this data, and curves showing the relationship between each parameter and stratum deformation are plotted.

[0102] Analysis of a large amount of data revealed a functional relationship between soil chamber pressure, tunneling speed, simultaneous grouting volume, and ground deformation. Taking soil chamber pressure and surface settlement as an example, surface settlement tends to decrease within a certain range as soil chamber pressure increases, but surface settlement slightly increases again when soil chamber pressure exceeds a certain critical value. Through mathematical modeling, quantitative correlation formulas between each parameter and ground deformation were fitted, such as the adjustment formulas for soil chamber pressure, tunneling speed, and simultaneous grouting volume given above. These formulas reflect the quantitative relationship between each parameter and ground deformation.

[0103] Based on the established quantitative correlations, combined with the protection requirements of existing railway lines and construction safety standards, an optimization algorithm is used to calculate the optimal parameter combination when the tunnel boring machine (TBM) crosses a risk source. For example, with the objective function of minimizing surface settlement and impact on the existing railway structure, and the constraints of the parameter value ranges, the optimization algorithm solves for the optimal combination of soil pressure, tunneling speed, and synchronous grouting volume. In actual construction, the parameters are continuously adjusted based on real-time monitoring data and calculation results to approximate the optimal parameter combination, thereby minimizing the impact on the strata and existing railway lines while ensuring construction safety.

[0104] By adjusting parameters such as soil chamber pressure, tunneling speed, and synchronous grouting volume in real time based on surface settlement monitoring data, it is possible to more accurately adapt to changes in the strata and effectively control strata deformation. For example, properly adjusting the soil chamber pressure can balance strata pressure and prevent strata heave or settlement caused by improper soil chamber pressure; precisely controlling the tunneling speed can avoid uneven disturbance to the strata caused by excessively fast or slow speeds; and accurately adjusting the synchronous grouting volume can promptly fill the shield tail gap and reduce surface settlement. Through the coordinated adjustment of these parameters, strata deformation is controlled within a small range, ensuring the safe operation of existing lines.

[0105] Establishing a quantitative correlation between various parameters and ground deformation, and determining the optimal parameter combination, makes the construction process more scientific and rational. Construction personnel can predict potential ground deformation during construction based on the quantitative relationship and optimal parameter combination, and take timely adjustments to avoid construction accidents caused by unreasonable parameters. This greatly improves the safety and reliability of shield tunneling construction and reduces adverse impacts on existing structures and the surrounding environment.

[0106] By continuously optimizing parameter combinations, not only can construction safety be ensured, but construction efficiency and quality can also be improved. For example, reasonable adjustments to the tunneling speed and grouting volume can reduce the number and duration of tunnel boring machine downtime, thereby increasing tunneling efficiency; precise parameter control can make the tunnel excavation profile more regular, reduce over-excavation and under-excavation, improve tunnel construction quality, and lay a solid foundation for subsequent tunnel lining and track laying.

[0107] In some examples, during the shield tunneling construction in step S4, when the shield tunnel crosses existing lines and risk sources, the soil chamber pressure is stably controlled at 1.0~1.4 bar with a fluctuation range of ≤±0.2 bar, the tunneling speed is stably controlled at 40~50 mm / min, and the tunneling is maintained at a uniform speed and continuous passage. The amount of excavated soil is controlled by volume and weight, with the amount of excavated soil per ring controlled at 46.1±2 m³. The horizontal attitude of the shield is controlled within ±20 mm, the vertical attitude front point is controlled within ±20 mm, and the rear point is controlled within -30~-10 mm. The single correction amount does not exceed 4 mm / m.

[0108] For example, multiple high-precision pressure sensors are evenly installed on the soil chamber wall of the tunnel boring machine (TBM), such as the PA-100 model with an accuracy of ±0.01 bar. These sensors collect soil chamber pressure data in real time and synchronously feed the data back to the monitoring system in the TBM operator's cab via data transmission lines. Operators can visually view the real-time values ​​and variation curves of the soil chamber pressure on the monitoring system's display screen.

[0109] When the soil chamber pressure is within the normal range of 1.0 - 1.4 bar and the fluctuation range is ≤ ±0.2 bar, the tunnel boring machine (TBM) continues to advance while maintaining the current tunneling parameters. Once the soil chamber pressure exceeds this fluctuation range, the monitoring system immediately issues an alarm. If the pressure drops below 0.8 bar (1.0 - 0.2 bar), the operator first reduces the speed of the screw conveyor to slow down the soil discharge rate and reduce the amount of soil discharged from the soil chamber. Simultaneously, the thrust of the propulsion cylinder is appropriately increased to propel the TBM forward, compressing the soil within the soil chamber and restoring the pressure. For example, when the soil chamber pressure drops to 0.7 bar, the screw conveyor speed is reduced from 25 r / min to 20 r / min, and the thrust of the propulsion cylinder is increased from 12000 kN to 13000 kN. After a period of adjustment, the soil chamber pressure gradually recovers to the range of 1.0 - 1.4 bar. If the soil chamber pressure is higher than 1.6 bar (1.4 + 0.2), increase the speed of the screw conveyor to improve the soil discharge rate, while reducing the thrust of the propulsion cylinder to lower the soil chamber pressure. For example, when the soil chamber pressure reaches 1.7 bar, increase the screw conveyor speed to 30 r / min and reduce the propulsion cylinder thrust to 11000 kN.

[0110] In addition to adjusting in real time based on pressure changes, operators also conduct comprehensive analysis of data from various aspects, including the tunnel boring machine's (TBM) excavation speed, cutterhead torque, and geological characteristics. Specialized data analysis software is used to predict trends in soil chamber pressure. For example, by studying historical data and analyzing the geological conditions of the current excavation section, potential changes in soil chamber pressure during subsequent excavation can be predicted. If an upward trend in soil chamber pressure is predicted, the excavation speed is appropriately reduced in advance, and the excavation speed of the screw conveyor is increased to prevent the soil chamber pressure from exceeding the control range.

[0111] Before the tunnel boring machine (TBM) crosses existing railway lines and potential risk sources, technicians input the set tunneling speed value on the control panel in the TBM operator's cab, based on the structural characteristics of the existing railway line, geological conditions, and the performance of the TBM. The tunneling speed is set between 40 and 50 mm / min. For example, based on the preliminary investigation of the anhydrous sand layer and factors such as the burial depth and structural form of the existing railway line, the tunneling speed for this crossing was determined to be 45 mm / min.

[0112] To ensure continuous and uniform tunneling by the tunnel boring machine (TBM), an advanced hydraulic proportional control system is employed in the propulsion system. This system precisely adjusts the pressure and flow rate of the propulsion cylinders to ensure stable extension and retraction speeds. The monitoring system tracks the tunneling speed in real time, automatically adjusting itself in case of fluctuations. If the speed drops to 35 mm / min, the system automatically increases the pressure of the propulsion cylinders to restore speed; if the speed exceeds 55 mm / min, it automatically decreases the pressure to reduce speed. Simultaneously, the construction process is optimized, such as by preparing all necessary materials and tools for segment assembly in advance. Once one ring is excavated, segment assembly can be performed quickly and efficiently, minimizing TBM downtime and ensuring continuous and uniform passage of the TBM through existing railway lines and potential hazards.

[0113] During tunneling, operators do not maintain a fixed speed but adjust it in real time based on actual conditions such as soil chamber pressure, cutterhead torque, and changes in the geological formation. When the formation becomes looser and the soil chamber pressure tends to increase, the tunneling speed is appropriately reduced to 40 mm / min, while closely monitoring changes in soil chamber pressure. When the formation is relatively stable and all parameters are normal, the tunneling speed can be maintained at 45-50 mm / min.

[0114] A high-precision ultrasonic volumetric flow meter is installed at the outlet of the screw conveyor. This flow meter can measure the volume of excavated soil in real time and accurately by utilizing the propagation characteristics of ultrasonic waves in materials. For each ring excavated (assuming a ring length of 1.5m), the theoretical excavated soil volume V = π × (26)² × 1.5 = 42.41m³ can be calculated based on the tunnel excavation diameter (set as 6m). Considering that there will be some over-excavation in actual excavation, the excavated soil volume per ring is set to be controlled at 46.1 ± 2m³. When the measured excavated soil volume exceeds 48.1m³ (46.1 + 2), the screw conveyor automatically reduces its speed to reduce the excavated soil volume; when the excavated soil volume is lower than 44.1m³ (46.1 - 2), the screw conveyor speed is appropriately increased to increase the excavated soil volume. For example, when the volumetric flow meter shows that the excavated soil volume reaches 48.5m³, the screw conveyor speed is reduced from 25r / min to 22r / min, so that the excavated soil volume is gradually reduced to within the control range.

[0115] A high-precision weighing platform is installed below the screw conveyor outlet. Multiple weighing sensors are mounted on the platform to form a weighing system, which measures the weight of the excavated soil in real time. Based on the average density of the sand (assumed to be 1.8 t / m³), the weight range corresponding to the excavation volume per ring is calculated to be from 44.1 × 1.8 = 79.38 t to 48.1 × 1.8 = 86.58 t. When the excavated weight exceeds this range, the excavation volume is controlled by adjusting the screw conveyor speed. For example, when the excavated weight reaches 88 t, the screw conveyor speed is reduced to decrease the excavation volume; when the excavated weight is 78 t, the screw conveyor speed is increased to increase the excavation volume.

[0116] Operators precisely control the amount of excavated soil by combining volume and weight measurements. Simultaneously, they adjust the control range based on geological variations, such as the density and moisture content of the sand layer. In denser sand layers, the upper limit of the control range can be appropriately reduced; in looser sand layers, the lower limit can be appropriately increased. For example, in an area with high sand density, the control range for the excavated soil is adjusted to 46.1 ± 1.5 m³.

[0117] The tunnel boring machine (TBM) is equipped with an advanced guidance system, such as the commonly used German VMT guidance system. This system uses multiple measuring prisms and laser targets installed at different locations within the TBM, employing laser ranging and angle measurement principles to measure the TBM's horizontal attitude in real time. The guidance system transmits the measurement data to the monitoring system in the operator's cab, displaying the TBM's horizontal deviation in intuitive graphical and precise digital form. When the TBM's horizontal attitude deviation exceeds ±20mm, the monitoring system issues an alarm. Operators adjust the TBM's horizontal attitude by adjusting the propulsion cylinder groupings, changing the thrust of different parts of the propulsion cylinders. For example, when the TBM deviates 25mm to the right, the thrust of the left propulsion cylinder is increased, and the thrust of the right propulsion cylinder is decreased, causing the TBM to gradually deviate to the left, restoring it to the allowable horizontal attitude range. Simultaneously, the guidance system's measurement data is manually verified at regular intervals (e.g., 5m) to ensure data accuracy.

[0118] Similarly, the guidance system is used to monitor the deviations of the tunnel boring machine's (TBM) vertical attitude at the front and rear points in real time. The front point deviation is controlled within ±20mm, and the rear point deviation within -30 to -10mm. When the front point deviation exceeds ±20mm, such as an upward deviation of 25mm, the attitude is corrected by adjusting the TBM's pitch angle. Specifically, the thrust of the lower propulsion cylinders is appropriately increased while the thrust of the upper propulsion cylinders is decreased, causing the TBM head to adjust downwards. For the rear point deviation, if the deviation exceeds the -30 to -10mm range, such as a downward deviation of -35mm, the tail clearance and propulsion cylinder thrust distribution are adjusted to cause the tail of the TBM to adjust upwards. During the adjustment process, close attention is paid to the TBM's attitude changes to avoid over-adjustment that could cause the attitude to exceed the range again. For example, when adjusting the rear point attitude, the propulsion cylinder thrust is adjusted in small increments each time, gradually bringing the rear point attitude within a reasonable range.

[0119] To prevent excessive disturbance to the strata caused by large single corrections, the regulation that the single correction amount should not exceed 4mm / m is strictly enforced. During attitude adjustments, operators precisely calculate the required change in thrust of the propulsion cylinders based on data provided by the guidance system, and make adjustments gradually. For example, if the tunnel boring machine (TBM) needs to be corrected to the left by 15mm, and the current TBM speed is 45mm / min, according to the requirement that the single correction amount should not exceed 4mm / m, each adjustment of the propulsion cylinder thrust should ensure that the TBM's leftward deviation does not exceed 4 × 100045 = 0.18mm. This correction is completed gradually in multiple stages to ensure stable TBM attitude adjustments and minimize disturbance to the strata.

[0120] Maintaining stable soil chamber pressure within 1.0-1.4 bar with fluctuations ≤ ±0.2 bar ensures that the pressure impact of the tunnel boring machine (TBM) on the existing railway line's underlying strata remains within a small and stable range during tunneling. This effectively prevents ground deformation caused by abnormal soil chamber pressure, thus guaranteeing the structural safety and normal operation of the existing railway line. A uniform and continuous tunneling speed avoids uneven ground disturbance caused by speed variations, further reducing the impact on the existing railway line. Accurate control of excavated soil prevents over-excavation or under-excavation that could lead to ground cavities or uplift, protecting the stability of the surrounding strata. Reasonable TBM attitude control ensures that the TBM advances along the designed route when crossing the existing railway line, preventing deviations that could cause compression or collisions with the existing structure. This comprehensive approach ensures the safety of the existing railway line during tunnel crossings, reduces the risk of interference with existing line operations, and safeguards passenger safety and operational order.

[0121] Precise control of soil pressure, tunneling speed, excavation volume, and shield attitude minimizes ground disturbance during tunneling in anhydrous sand layers. Stable soil pressure and uniform tunneling speed prevent excessive compression or suction of the sand layer, reducing particle displacement and rearrangement. Strict control of excavation volume prevents the formation of cavities in the strata, reducing the risk of surface subsidence and collapse. Reasonable shield attitude adjustment and single-correction control avoid strong disturbances to the strata caused by sudden changes in shield attitude, maintaining the original structure and stability of the anhydrous sand layer. This is beneficial to the protection of the surrounding environment, reduces the impact of construction on surrounding buildings, roads, and other infrastructure, and lowers potential disputes and repair costs.

[0122] Strict control of various parameters ensured the construction quality of the shield tunnel. Stable excavation parameters resulted in a smooth tunnel face, reduced voids behind the tunnel lining, facilitated subsequent grouting and filling operations, improved the adhesion between the tunnel lining and the strata, and enhanced the stability and durability of the tunnel structure. Accurate shield attitude control ensured that the tunnel axis met design requirements, guaranteed the tunnel's forming quality, and provided a solid foundation for subsequent track laying and equipment installation. Simultaneously, reasonable parameter control reduced shield machine malfunctions and ground accidents caused by unreasonable parameters, avoided construction delays, improved construction efficiency, ensured timely project completion, and saved time and management costs.

[0123] In some examples, during the shield tunneling construction in step S4, the grouting volume was increased to 1.2 times that of the ordinary section, 5.4 m³ / ring, and the grouting pressure was controlled at 2.0~4.0 bar; secondary grouting was carried out after the segments exited the shield tail, and secondary grouting was carried out every 3 rings when crossing the risk source section, with the grouting pressure ≤0.5 MPa; when passing under the power tunnel, deep hole grouting was carried out through the reserved grouting holes after the segments exited the shield tail, with the grouting pressure controlled at 0.5~0.8 MPa, to supplement and reinforce the soil below the risk source.

[0124] For example, when a tunnel boring machine (TBM) crosses an existing railway line or a high-risk section, the construction team determines the grouting volume for the crossing section in advance based on the grouting volume of the ordinary section. Given that the grouting volume for the ordinary section is assumed to be 4.5 m³ / ring, the grouting volume is increased to 1.2 times that of the ordinary section, i.e., 4.5 × 1.2 = 5.4 m³ / ring.

[0125] On the grouting system control panel of the tunnel boring machine, the grouting volume per ring is set to 5.4 m³. The grouting system is equipped with a high-precision flow sensor, such as the LWGY-100 turbine flow sensor, which can monitor the grouting flow rate in real time. When the grouting volume approaches the set value, the system automatically adjusts the speed of the grouting pump to ensure the grouting volume accurately reaches 5.4 m³. For example, when the grouting volume reaches 5.0 m³, the system gradually reduces the speed of the grouting pump to stabilize the final grouting volume at 5.4 m³.

[0126] Install high-precision pressure sensors, such as the PT124G-211 pressure sensor, on the grouting pipeline. The accuracy can reach ±0.05 bar, which can monitor the grouting pressure in real time and feed the pressure data back to the monitoring system in the tunnel boring machine's control room.

[0127] When the grouting pressure drops below 2.0 bar, the monitoring system issues an alarm. Operators then increase the grouting pressure by adjusting the pressure regulating valve on the grouting pump. For example, when the pressure reading is 1.8 bar, the pressure regulating valve is gradually adjusted to raise the grouting pressure to 2.0 bar. Within the range of 4.0 bar. When the grouting pressure exceeds 4.0 bar, the opposite operation should be performed, reducing the grouting pressure. Simultaneously, operators should closely monitor pressure changes and fine-tune the pressure as needed based on formation conditions and grouting effectiveness. For example, in denser sand layers, the grouting pressure can be appropriately increased to 3.5 bar. 4.0 bar to ensure that the slurry can fully fill the formation pores.

[0128] During the segment production process, secondary grouting holes are pre-drilled on the segments according to design requirements. After the segments are transported to the construction site, the grouting holes are checked for blockage; any blockages are cleaned promptly. Simultaneously, the necessary equipment and materials for secondary grouting are prepared, including grouting pumps, grouting pipelines, cement grout, or other suitable grouting materials.

[0129] A secondary grouting device is installed on the tunnel boring machine, connecting the grouting pump, grouting pipeline, and grouting holes on the tunnel segments. Ensure the connection is secure and leak-free.

[0130] When traversing a high-risk section, after the tunnel segment exits the shield tail, grouting is performed on the corresponding segments according to the requirement of secondary grouting every three rings. Operators start the grouting pump and inject the prepared grouting material into the strata behind the tunnel segment through the grouting pipeline.

[0131] During grouting, the grouting pressure is strictly controlled to be ≤0.5MPa using the pressure regulating device and pressure sensor on the grouting pump. When the pressure approaches 0.5MPa, the grouting speed is reduced to prevent excessive pressure from damaging the strata and tunnel segments. For example, when the grouting pressure reaches 0.45MPa, the flow rate of the grouting pump is reduced from 10L / min to 5L / min to stabilize the grouting pressure within the allowable range.

[0132] Before the shield tunnel passes under the power tunnel, a deep-hole grouting scheme is designed based on the location, depth, and surrounding geological conditions of the power tunnel. This includes determining the layout, depth, angle of the grouting holes, and the mix proportions of the grouting materials. For example, the grouting holes are located within a certain range after the tunnel segments exit the shield tail, and the hole depth is determined to be 5 mm based on the reinforcement requirements of the soil beneath the power tunnel. The grouting hole is 8m long, and the angle between it and the tunnel axis is set to 30° based on the actual situation. 45°.

[0133] Prepare the necessary equipment and materials for deep hole grouting, including drilling rigs, grouting pumps, grouting pipelines, and specially designed grouting perforated pipes. Debug the drilling rig to ensure it can accurately drill holes at the designed angle and depth. Inspect the grouting pump and grouting pipelines to ensure they have good sealing performance and can withstand the corresponding grouting pressure.

[0134] Once the tunnel boring machine (TBM) segments have emerged from the tail shield, drilling operations are immediately commenced using a drilling rig through the pre-drilled grouting holes on the segments. During drilling, close monitoring of the drilling rig's progress, including parameters such as drilling speed and torque, is essential to ensure drilling quality. Once the borehole reaches the designed depth, a specially designed grouting perforated pipe is inserted into the hole.

[0135] Start the grouting pump and inject the prepared grouting material (such as cement-water glass double-liquid grout) into the soil beneath the power tunnel through the grouting pipe. Strictly control the grouting pressure at 0.5 liters using the pressure regulating device and pressure sensor on the grouting pump. Within the range of 0.8 MPa. During the grouting process, observe the changes in grouting pressure and grouting volume. If a sudden increase or decrease in pressure or abnormal grouting volume is found, stop grouting immediately, analyze the cause, and take appropriate measures. For example, if the grouting pressure suddenly rises to 0.9 MPa, stop grouting and check whether the grouting pipeline is blocked or whether there are abnormal structures in the soil.

[0136] Increasing the grouting volume in sections crossing existing railway lines and high-risk areas can more fully fill the voids in the soil formed after tunnel boring, reducing the possibility of ground settlement. The increased grouting volume allows the grout to better penetrate the pores of the anhydrous sand layer, binding loose sand particles together, improving soil cohesion and friction, enhancing ground stability, and providing more reliable support for existing railway lines and high-risk areas.

[0137] Secondary grouting further filled the voids caused by soil deformation after the segments exited the shield tail, and reinforced the strata crossing the risk source section, effectively controlling the later settlement of the strata and ensuring the long-term stability of the existing line structure.

[0138] Deep-hole grouting was carried out when tunneling under the power tunnel to reinforce the soil beneath it, thereby improving the bearing capacity of the soil in the area and preventing deformation of the soil beneath the power tunnel due to shield tunneling. This protected the safety of the power tunnel and ensured the stability of the power supply.

[0139] Strictly control the grouting pressure to avoid damage to existing railway structures, power tunnels, and other risk sources caused by excessive grouting pressure. Appropriate grouting pressure ensures effective filling of the strata with grout without causing excessive compression or disturbance to surrounding structures, thus guaranteeing the normal operation of existing railway lines and the safety of risk sources.

[0140] Through a series of grouting measures, the impact of the tunnel boring machine (TBM) crossing on the surrounding strata and structures was reduced as a whole, and the probability of safety accidents such as deformation of existing tracks and rupture of power tunnels caused by strata deformation was lowered, thus ensuring the safe operation of urban infrastructure.

[0141] Reasonable grouting parameters and processes ensured the stability of the surrounding strata, creating favorable conditions for tunnel construction. Stable strata helped the tunnel boring machine (TBM) maintain a good tunneling posture, reducing problems such as TBM deviation and uneven segment installation caused by unstable strata, thus improving the construction accuracy and forming quality of the tunnel.

[0142] Effective grouting reinforcement also enhances the bond between the tunnel lining and the stratum, making the tunnel structure more stable, extending the tunnel's service life, and reducing later maintenance costs.

[0143] In some examples, during the construction of the tunnel entrance in step S5, welded steel pipes with a diameter of 32×3.25mm and a length of 3.5m are used for the advance guide pipes. They are arranged in a double-row, quincunx pattern along the 150° range of the outer contour arch of the tunnel entrance, with a circumferential spacing of 300mm and a grouting pressure of 0.3~0.5MPa. The retaining piles are removed manually using hand-held pneumatic picks. The removal sequence is from top to bottom and from the center to both sides, layer by layer. Three grid steel frames are densely arranged at the entrance, with a spacing of 300mm. Double-layer Φ20 connecting bars are used to stagger the inner and outer sides. 300mm thick C25 concrete is sprayed to complete the support and closure.

[0144] For example, within 1m of the tip of the small guide pipe, use a bench drill to drill overflow holes with a diameter of 6-8mm, spaced 100mm apart in a quincunx pattern. After drilling, clean the iron filings inside the steel pipe to prevent clogging of the overflow holes and affecting the grouting effect.

[0145] Before the construction of the gate, the outer contour of the gate was accurately measured using a total station and a level, and the layout positions of the small guide pipes were marked on the working face.

[0146] Along the outer contour of the arched section of the gate, small guide pipes are laid out in a horizontal, double-row, quincunx pattern. The first row of guide pipes is installed first, using a pneumatic drill to drive them into the ground at the designed angle and position. The driving angle of the guide pipes is strictly controlled horizontally, with an error not exceeding ±2°, ensuring that the guide pipes are on the same plane. The circumferential spacing is 300mm, and a steel ruler is used for measurement during construction to ensure that the spacing error is controlled within ±10mm.

[0147] After the first row of small guide pipes is completed, the second row of small guide pipes is constructed in the same way. The longitudinal spacing between the two rows of small guide pipes is 300mm, and a steel ruler is used for precise measurement and control.

[0148] During construction, to ensure the stability of the small guide tube, a reinforcing rib with a length of 150-200mm is welded to the tail end of the small guide tube. The reinforcing rib is welded perpendicular to the small guide tube, and the weld is full to ensure the welding strength.

[0149] The grouting material used is a cement-water glass two-component grout. According to the designed mix ratio, cement and water are first mixed to form a cement slurry with a water-cement ratio of 1:1. Then, water glass is slowly added to the cement slurry at a volume ratio of 1:1, while stirring continuously to ensure uniform mixing. The prepared grout is then injected into a small conduit using a grouting pump. Before grouting, the grouting equipment is checked for proper operation, and the pipe connections are verified to be tight and leak-free.

[0150] The grouting pressure is controlled between 0.3 and 0.5 MPa, and is monitored in real time using a pressure gauge on the grouting pump. During the grouting process, close observation of changes in grouting pressure and grout volume is necessary. When the grouting pressure reaches 0.5 MPa and the grout volume decreases significantly, the grouting of the small-diameter pipe is considered essentially complete, and grouting should be stopped. If a sudden increase or decrease in grouting pressure is observed during the grouting process, grouting should be stopped immediately, the cause investigated, and appropriate measures taken, such as checking for pipe blockage, ground cavities, or other problems.

[0151] Following a top-down, center-to-side, layer-by-layer demolition sequence, construction workers used pneumatic picks to break down the retaining piles. Starting from the top of the piles, they began demolishing along the center line, breaking the concrete into smaller pieces for easier cleanup. During the demolition process, care was taken to control the impact force and demolition range of the pneumatic pick to avoid excessive disturbance to the surrounding soil and existing structures. Larger concrete blocks were further broken into smaller fragments using the pneumatic pick for easier cleanup and transportation.

[0152] After each layer is broken (approximately 300-500mm in height), promptly clean up the resulting debris and soil to maintain a clean and unobstructed construction site.

[0153] When breaking down the retaining piles near the opening, construction workers must operate with extra caution to avoid damaging the soil at the opening and the subsequent grating steel frame to be constructed.

[0154] The Φ20 connecting bars and grating steel frame are fabricated in the processing plant. The grating steel frame is welded from Φ22 steel bars, and the welding quality must meet relevant standards, with full welds and no defects such as slag inclusions or porosity. The fabricated grating steel frame is transported to the construction site, and is hoisted to the opening position using a gantry crane or with manual labor.

[0155] Three grating steel frames are installed closely at the tunnel entrance, with the spacing between the frames strictly controlled at 300mm, measured and adjusted using a steel ruler. During installation, ensure that the grating steel frames are perpendicular to the tunnel axis, with the verticality error controlled within ±2°.

[0156] Double-layered Φ20 connecting ribs are arranged alternately inside and outside to connect adjacent grating steel frames into a whole. The connecting ribs are welded to the grating steel frame, and the weld length is not less than 10d (d is the diameter of the connecting rib) to ensure a firm connection.

[0157] C25 concrete was used for shotcreting. Before spraying, the shotcreting machine was checked to ensure it was operating normally and that the material delivery pipeline was unobstructed and free of blockages. The surface of the surrounding rock at the tunnel entrance was cleaned, removing loose soil, rocks, and debris, and the rock surface was blown clean with high-pressure air. To ensure uniform shotcrete thickness, a thickness control marker was placed on the tunnel wall every 1-2 meters.

[0158] When spraying concrete, the working air pressure of the spraying machine should be controlled at 0.3-0.5MPa, the distance between the nozzle and the surface to be sprayed should be maintained between 0.8-1.2m, and the spraying angle should be perpendicular to the surface to be sprayed.

[0159] The concrete should be sprayed in a spiral motion from bottom to top, with the wall sprayed first and then the arch. During the spraying process, the concrete should be closely observed, and the spraying parameters should be adjusted in a timely manner to ensure that the concrete surface is smooth and free of defects such as honeycomb or pitting.

[0160] The shotcrete should be applied in 2-3 layers, with each layer being 100-150mm thick. After each layer is applied, allow it to initially set before applying the next layer. After spraying, the concrete should be cured promptly for at least 7 days.

[0161] Pre-installed small guide pipes with a diameter of 32×3.25mm and a length of 3.5m were horizontally arranged in a double-row, quincunx pattern along the outer contour of the arch of the horse-head gate. Grouting was then performed to integrate the small guide pipes with the surrounding soil, effectively reinforcing the soil of the arch of the horse-head gate, improving the soil's self-stability, reducing the risk of soil collapse, and providing a stable working space for subsequent construction.

[0162] Three steel grating frames are densely arranged at the opening with a spacing of 300mm. Double-layer Φ20 connecting bars are staggered inside and outside to enhance the overall strength and stability of the steel grating frames. They can better withstand soil pressure and work together with the 300mm thick C25 sprayed concrete to form a solid support structure, ensuring the stability of the gate during construction and use.

[0163] The retaining piles were removed manually using hand-held pneumatic picks. Compared to methods such as blasting, this method allows for more precise control of the removal range and intensity, reducing disturbance to the surrounding soil and existing structures. The removal sequence, proceeding layer by layer from top to bottom and from the center outwards, further minimized soil disturbance, ensuring the stability of the soil around the gate and reducing the impact on the existing railway line and the surrounding environment.

[0164] The strict adherence to construction techniques, including advanced small-diameter grouting, retaining pile removal, lattice steel frame installation, and shotcrete application, ensured the safety and quality of the gatehouse construction at every stage. The stable gatehouse structure reduced the probability of collapses and other safety accidents during construction, ensuring the safety of construction personnel. Simultaneously, the construction techniques, meeting design requirements, guaranteed the support strength and stability of the gatehouse, creating favorable conditions for subsequent cut-and-cover tunnel construction and ensuring the overall quality of the project.

[0165] In some examples, during step S6, the excavation and support of the cut-and-cover tunnel, the excavation method is adapted to the tunnel cross-section size. For example, for the 6.5m QA / QD type cross-section, the upper and lower bench method with 2 pilot tunnels is used for excavation, with core soil reserved on the upper bench and the spacing between the upper and lower benches staggered by 5-10m; for the 9.4m QC type cross-section, the CRD method with 4 pilot tunnels is used for excavation, with each pilot tunnel staggered by 5-7m; and for the 14.1m QB type cross-section, the double-side-wall pilot tunnel method with 9 pilot tunnels is used for excavation. Each pilot tunnel is constructed strictly according to the design sequence, with the excavation of the same numbered chambers on both sides staggered by 8-10m.

[0166] For example, adapting different excavation methods to the tunnel cross-section dimensions can fully leverage the advantages of each method and effectively address the construction challenges posed by different cross-section sizes. For smaller cross-sections of 6.5m, the step-down method is used, which is relatively simple to construct and allows for rapid progress. For medium-sized cross-sections of 9.4m, the CRD method is used, effectively controlling surrounding rock deformation through reasonable pilot tunnel layout and construction sequence. For larger cross-sections of 14.1m, the double-sidewall pilot tunnel method is used; the excavation of multiple pilot tunnels and strict staggered construction ensure the safety and stability of large-section tunnels under complex geological conditions such as waterless sand layers.

[0167] The measures adopted in different excavation methods, such as reserving core soil, staggered excavation of pilot tunnels, and setting up temporary supports, can effectively control the deformation of the surrounding rock. Reserving core soil provides support for the tunnel face and reduces the risk of soil collapse; staggered excavation of pilot tunnels avoids stress concentration in the surrounding rock, allowing the stress in the surrounding rock to be released gradually; temporary supports enhance the overall stability of the tunnel surrounding rock, thereby effectively controlling the deformation of the surrounding rock and ensuring the safety of the existing line and the surrounding environment.

[0168] Each construction method was strictly implemented in accordance with design requirements and construction specifications, with rigorous control over every stage from excavation to support. Precise surveying and setting out, reasonable blasting design, timely and effective initial support, and a scientific construction sequence ensured the safety and quality of tunnel construction. These measures reduced the probability of safety accidents during construction, ensured the stability and durability of the tunnel structure, and laid a solid foundation for subsequent operation and use.

[0169] In some examples, during step S6, the excavation and support of the cut-and-cover tunnel section, the excavation advance per cycle is 0.5m. Immediately after excavation, initial shotcrete is applied to seal the rock surface. Subsequently, a grid steel frame is erected, a Φ6@150×150mm steel mesh is installed, and longitudinal connecting bars are welded. Two Φ32×3.25mm anchor pipes with a length of 2m are driven at the foot of each arch. Finally, C25 concrete is sprayed to the designed thickness, with a spray layer thickness of 300mm for QA / QD type sections and 350mm for QB / QC type sections, ensuring that the initial support is sealed into a ring in a timely manner.

[0170] For example, the excavation advance is controlled at 0.5m per cycle, and shotcrete is immediately applied to seal the rock surface after excavation. This rapid sealing measure effectively prevents the anhydrous sand layer from loosening and collapsing due to prolonged exposure, thus stabilizing the surrounding rock in a timely manner. Subsequent procedures such as the erection of the grid steel frame, the hanging of the steel mesh, the welding of longitudinal connecting bars, and the installation of anchor pipes further enhance the strength and stability of the initial support, enabling it to withstand the pressure of the surrounding rock as quickly as possible and control its deformation.

[0171] The construction of the lattice steel frame, reinforcing mesh, longitudinal connecting bars, and shotcrete was carried out strictly in accordance with design requirements, ensuring the quality of the initial support. For example, the spacing, verticality, and closeness of the lattice steel frame to the surrounding rock, the specifications and connection methods of the reinforcing mesh, the welding quality of the longitudinal connecting bars, and the thickness and strength of the shotcrete were all effectively controlled. This ensured that the initial support could form a robust load-bearing structure, providing a guarantee for the safe construction and long-term stability of the tunnel.

[0172] By employing a reasonable construction sequence and timely construction measures, the initial support is ensured to be closed into a ring in a timely manner. For different types of cross-sections, close coordination is maintained at each construction stage according to their characteristics and construction methods, enabling the initial support to quickly form a closed structure. After the initial support is closed into a ring, the surrounding rock pressure can be effectively distributed evenly, improving the overall stability of the support structure, reducing the probability of safety accidents such as tunnel collapse, and ensuring the safe and smooth progress of the cut-and-cover tunnel construction.

[0173] In some examples, during the existing line connection construction in step S7, physical isolation is achieved by using 300mm thick brick partition walls and reinforced concrete structural columns to completely enclose the area to be excavated; static cutting strictly controls the weight of a single piece to ≤160kg to reduce vibration and damage to the existing structure; multiple waterproofing measures are implemented at the connection between the new and old structures, including grouting pipes, water-swellable waterproof sealant, and sealant, to ensure that the waterproofing quality of the joint meets the standards.

[0174] For example, a physical isolation structure consisting of a 300mm thick brick partition wall and reinforced concrete structural columns can effectively separate the area to be excavated from other parts of the existing railway line. The brick partition wall and structural columns possess sufficient strength and stability to not only prevent debris and dust from entering the existing railway line's operating area during construction, but also to some extent block the transmission of construction vibrations and noise, reducing the impact on the normal operation of the existing line. Fully enclosed fencing further enhances the isolation effect, improves the safety of the construction area, prevents unauthorized personnel from entering the construction site, and avoids safety accidents.

[0175] By strictly controlling the weight of each static cutting block to ≤160kg, vibration and damage to existing structures are significantly reduced during cutting. The smaller block weight results in less impact force during cutting, lowering the risk of cracks, loosening, or other damage caused by vibration, thus ensuring the safety and stability of the existing structure. This is crucial for projects like existing power lines, which have extremely high structural safety requirements, ensuring normal operation during connection construction and preventing structural damage from affecting their service life and operational safety.

[0176] Multiple waterproofing measures, including grouting pipes, water-swellable sealant, and sealant, were implemented at the junctions of new and old structures, forming a complete waterproofing system. The grouting pipes can be used to fill gaps at the junctions later, sealing any potential leakage channels. The water-swellable sealant expands upon contact with water, filling gaps and acting as a waterproof barrier. The sealant further enhances the waterproofing effect, preventing moisture penetration through the junctions. These multiple waterproofing measures work together to effectively ensure the quality of the joint waterproofing, preventing corrosion and damage to the existing structure due to leaks, extending the service life of the existing railway line, and guaranteeing its long-term safe operation.

[0177] In some examples, during steps S3 and S4, the tunnel segments are assembled using a staggered joint method. After positioning, the longitudinal bolts are initially tightened immediately, and then tightened again after the entire ring is assembled. A third tightening is performed after the segment exits the shield tail. The bolt torque is ≥100kN·m, the misalignment between adjacent ring segments is ≤5mm, and the misalignment between longitudinally adjacent segments is ≤6mm. Cement mortar is used for synchronous grouting, with a grouting pressure of 0.2~0.3MPa. The grouting volume is controlled at 1.6~1.7 times the volume of the voids in the tunnel segments, and the voids are filled densely.

[0178] For example, the staggered assembly method of the tunnel segments ensures a more uniform stress distribution among them, effectively improving the overall structural stability of the tunnel lining. Strict bolt tightening processes ensure a firm connection between the segments, better resisting ground pressure and various forces during tunnel boring machine (TBM) advancement. Three bolt tightening operations, gradually increasing bolt torque, further enhance the reliability of the segment connections, preventing increased segment misalignment or tunnel lining deformation due to loose bolts. Controlling the misalignment between adjacent ring segments to ≤5mm and between longitudinally adjacent segments to ≤6mm ensures the flatness of the tunnel wall, facilitating subsequent track laying and equipment installation. It also reduces localized stress concentration in the segments caused by excessive misalignment, extending the service life of the tunnel segments.

[0179] Cement mortar was used as the synchronous grouting material. Its good fluidity and strength after solidification effectively filled the structural voids behind the tunnel lining segments. The grouting pressure was reasonably controlled between 0.2 and 0.3 MPa, ensuring that the grout fully filled the voids while avoiding damage to the tunnel lining segments and the stratum due to excessive pressure. The grouting volume was controlled at 1.6 to 1.7 times the volume of the structural voids, ensuring that the voids were densely filled, reducing settlement and deformation of the stratum caused by the voids, ensuring the safe operation of the existing line, and also enhancing the bond between the tunnel lining and the stratum, thus improving the overall stability of the tunnel structure.

[0180] In some examples, during step S8, the tunneling measurement and shield receiving, connection measurements and traverse measurements are performed 80m, 50m, and 20m before the shield reaches the receiving shaft to verify the shield machine's attitude and tunnel axis. After entering the receiving reinforcement zone, the tunneling speed is reduced to 5-10mm / min, the soil chamber pressure is lowered to 0.8-1.2bar, and the total thrust is controlled at 900-1500t. After the shield machine has completely entered the receiving shaft, the 10 ring segments at the tunnel entrance are immediately grouted and sealed. First, a water-stop ring is installed, and then double-liquid grout and single-liquid grout are injected in stages until there is no leakage in the inspection hole.

[0181] For example, before the tunnel boring machine (TBM) reaches the receiving shaft, connection measurements and traverse measurements are conducted at different distances. Through multiple precise measurements and verifications of the TBM's attitude and the tunnel axis, deviations during the TBM's excavation process can be detected in a timely manner, and effective measures can be taken to adjust them. This ensures that the TBM can accurately reach the receiving shaft in the final stage, avoiding receiving failures or damage to the receiving shaft structure due to TBM attitude deviations, and guaranteeing the smooth progress of the tunnel boring construction.

[0182] After entering the receiving and reinforced area, parameters such as tunneling speed, soil chamber pressure, and total thrust are adjusted appropriately to ensure smooth tunneling by the tunnel boring machine (TBM) within the area. Reducing the tunneling speed minimizes disturbance to the strata, while lowering the soil chamber pressure and controlling the total thrust helps adapt to the geological conditions of the receiving and reinforced area. This avoids adverse effects on the strata and receiving shaft structure caused by excessive or insufficient pressure, ensuring the safety and stability of the receiving process and minimizing the impact on the surrounding environment.

[0183] After the tunnel boring machine (TBM) entered the receiving shaft, grouting was performed to seal the 10 rings of tunnel segments at the tunnel portal. First, a water-stop ring was installed, followed by the injection of double-liquid grout and single-liquid grout in stages. Through these multiple waterproofing measures, the voids behind the tunnel segments were effectively filled, preventing groundwater leakage. Rigorous inspection and repair ensured the waterproofing effect of the tunnel segments at the portal, guaranteeing the tunnel structure's waterproof performance and preventing problems such as water accumulation and structural corrosion inside the tunnel caused by portal leakage, thus extending the tunnel's service life.

[0184] In some examples, during step S9, the monitoring and dynamic adjustment of the entire process includes monitoring the vertical and horizontal settlement and displacement of the existing line, surface settlement, pipeline settlement, segment arch settlement and clearance convergence; automated monitoring collects data every 2 to 3 hours, manual monitoring is conducted 1 to 2 times per day during the crossing construction, and real-time monitoring is implemented when data is abnormal; the soil pressure, tunneling speed and grouting volume are adjusted in real time based on the monitoring data.

[0185] For example, monitoring points are set up at key parts of existing railway lines, such as track slabs and ballast. For instance, holes are drilled every 5 meters on the track slabs to insert specially made stainless steel measuring nails as vertical settlement monitoring points; and a reflecting prism is installed every 10 meters on the side of the ballast for horizontal displacement monitoring.

[0186] For vertical settlement, a high-precision electronic level, such as the Trimble Dini03 level, is used, with a measurement accuracy of ±0.3 mm / km. Leveling measurements are performed regularly at each monitoring point, and the vertical settlement is calculated by measuring the elevation changes at these points over different time periods. For horizontal displacement, a total station, such as the Leica TS16 total station, is used. Horizontal displacement data is obtained by measuring the coordinate changes of the reflecting prism. During the measurement process, the accuracy and stability of the instrument are ensured; the instrument is calibrated and leveled before each measurement.

[0187] Monitoring points are arranged at regular intervals on the ground surface above and around the shield tunnel. Using the tunnel centerline as a reference, a row of monitoring points is arranged every 3 meters on both sides, with a 5-meter interval between each row. The monitoring points are installed by drilling holes in the ground and embedding steel piles, with the top of the piles protruding 5-10 cm above the ground surface, and protective measures are implemented.

[0188] High-precision electronic levels are used for regular measurements. During each measurement, elevations are transferred from nearby benchmarks, and the elevation data at each monitoring point are recorded. The surface subsidence is calculated by comparing these elevations with the initial elevation. To minimize errors, the principle of "equal foresight and backsight distances" is followed during measurements, and the measurement route is kept as fixed as possible.

[0189] For underground pipelines within the construction impact area, the layout of monitoring points is determined based on the type, material, and importance of the pipelines. For important gas and water supply pipelines, a monitoring point is set every 10 meters. The monitoring points are fixed to the pipelines using clamps or welding to ensure a tight connection between the monitoring points and the pipelines.

[0190] Electronic levels are used to measure elevation changes at monitoring points to obtain pipeline settlement data. Care must be taken to avoid damaging the pipeline during the measurement process. Simultaneously, close communication should be maintained with the pipeline management unit to understand the original pipeline data and operational status, in order to better analyze the monitoring data.

[0191] On the tunnel lining segments, a settlement monitoring point is set at the crown every 10m, secured by attaching reflective sheets or installing measuring nails. On both sides of the same segment section, clearance convergence monitoring points are set up to obtain clearance convergence data by measuring the change in distance between the two points.

[0192] For crown settlement monitoring, a total station is used to measure the elevation changes of reflectors or measuring pins. For clearance convergence monitoring, a convergence meter is used. During each measurement, both ends of the convergence meter are fixed to the monitoring point, and the distance values ​​are read and recorded. By comparing with the initial values, the clearance convergence is calculated.

[0193] When monitoring data shows an increasing trend in vertical settlement or surface settlement of the existing railway line, and it is determined that this is caused by insufficient soil pressure leading to ground loss, the soil pressure should be appropriately increased based on the magnitude and rate of settlement. For example, if the vertical settlement rate of the existing railway line exceeds 0.5 mm / d, and data analysis determines that it is related to soil pressure, the soil pressure should be increased by 0.1 - 0.2 bar from the original set value.

[0194] Conversely, if the settlement gradually decreases and tends to stabilize, the soil pressure can be appropriately reduced to improve the tunnel boring machine's efficiency, provided that the strata stability is ensured. When reducing the soil pressure, each adjustment should not exceed 0.1 bar, and changes in monitoring data should be closely monitored.

[0195] If excessive surface subsidence or segment arch subsidence is detected, and analysis indicates that it is due to excessive ground disturbance caused by excessive tunneling speed, the tunneling speed should be reduced. For example, the tunneling speed can be reduced from 50 mm / min to 40 mm / min, while observing changes in settlement data. If the settlement rate slows down, the adjustment measures are effective; if the subsidence remains significant, the tunneling speed should be further reduced or other measures should be taken.

[0196] When monitoring data shows that the strata are stable and all settlement indicators are within the allowable range, the tunneling speed can be appropriately increased to accelerate the construction progress. When increasing the tunneling speed, the increase should not exceed 10 mm / min each time, and monitoring data should be continuously monitored to ensure construction safety.

[0197] If monitoring reveals that the grouting behind the tunnel segments is not dense enough, leading to increased settlement of the tunnel segment arch or ground surface settlement, the grouting volume should be appropriately increased. For example, the grouting volume can be increased by 10% to 20% based on the original design volume to fill the voids behind the tunnel segments and reduce ground settlement.

[0198] If monitoring data analysis reveals that the grouting volume is too high and may adversely affect the existing railway line or the surrounding environment, such as causing ground uplift or deformation of the existing railway line structure, the grouting volume should be reduced. When reducing the grouting volume, each adjustment should not exceed 10% of the original grouting volume, and monitoring data should be closely observed to ensure that the adjustment of the grouting volume is reasonable.

[0199] By monitoring various aspects such as vertical and horizontal settlement and displacement of existing lines, surface settlement, pipeline settlement, segment arch settlement, and clearance convergence, a comprehensive and systematic understanding of the impact of tunnel boring machine (TBM) construction on existing lines and the surrounding environment can be achieved. Accurate acquisition of data from each monitoring item provides a reliable basis for assessing construction safety and the extent of impact on existing structures, and helps to identify potential problems in a timely manner.

[0200] By appropriately setting the frequency of automated and manual monitoring, and implementing real-time monitoring when data anomalies occur, various changes during the construction process can be captured promptly. Through real-time monitoring data, construction parameters such as soil chamber pressure, tunneling speed, and grouting volume can be adjusted in a timely manner, ensuring the construction process remains under control. This effectively avoids problems such as excessive ground deformation and damage to existing railway structures caused by unreasonable construction parameters, thus ensuring construction safety and project quality.

[0201] By adjusting construction parameters in real time based on monitoring data, dynamic management of the construction process is achieved. This dynamic adjustment mechanism can flexibly respond to various complex geological conditions and changes in the construction environment according to the actual construction situation, optimize construction plans, improve construction efficiency, and at the same time minimize the impact on existing lines and the surrounding environment, ensuring the normal operation of existing lines and the safety of surrounding residents.

[0202] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for micro-disturbance construction of subway shield tunneling combined with underground excavation through existing railway lines in anhydrous sand layers, characterized in that... The construction steps include the following: S1. Surveying and setting out and monitoring system layout: Using total station and level instrument to survey the shield tunneling line, the outline of the cut-and-cover excavation, and the position of the gate, set up surface, pipeline, and building settlement observation points in the construction impact area, set up automated monitoring sections and install monitoring elements in the existing operating line, and collect and determine the initial monitoring values. S2. End reinforcement and advanced support operations: For the shield launching and receiving ends, plain piles combined with sleeve valve pipe grouting are used to reinforce the strata. For the tunnel excavation and before each cycle of excavation, advanced small guide pipes are installed in the arch and grouting is completed to form an advanced reinforcement ring outside the excavation outline. S3. Shield launching and trial excavation operations: install launching bracket and reaction frame, complete shield machine assembly and debugging and tunnel portal retaining structure demolition, and control shield machine to cut into the tunnel face to complete launching; S4. Shield tunneling construction: When the shield tunnel crosses over or sideways through existing lines and surrounding risk sources, it shall be continuously excavated at a uniform speed, and grouting operations shall be carried out simultaneously throughout the process to control the shield attitude and the single correction amplitude, and complete the shield tunneling section construction. S5. Construction of the tunnel gate: After the main structure of the shield receiving shaft is completed, double rows of advanced small guide pipes are installed along the outer contour of the tunnel gate and grouting is used for reinforcement. The retaining piles are broken in sequence by manual pneumatic picks. The grid steel frame is densely arranged at the tunnel entrance and the connecting bars are welded. The tunnel gate is supported and closed by spraying concrete. S6. The excavation and support of the cut-and-cover tunnel are carried out in stages according to the sectional excavation method. After each designed advance is excavated, the initial shotcrete, grid steel frame erection, steel mesh hanging, anchor pipe construction and re-shotcrete operation are completed immediately to make the initial support quickly closed into a ring. S7. Existing line connection construction: At the connection point between the tunnel section and the existing line, first set up brick partition walls and structural columns to complete physical isolation, use wire saw to cut the existing structure into sections and statically, and implement multiple waterproofing measures according to design requirements to complete the connection between the old and new structures. S8. Breakthrough Measurement and Shield Reception: Before the shield reaches the receiving shaft, multiple breakthrough measurements are completed according to the design mileage. The shield attitude is checked and adjusted. After entering the receiving reinforcement area, the tunneling parameters are adjusted to complete the tunneling of the receiving section. After the shield enters the receiving shaft, the segments at the tunnel entrance are immediately grouted and sealed. S9. Full-process monitoring and dynamic adjustment: Continuous monitoring of existing line structure deformation, surface settlement, pipeline settlement, and tunnel structure deformation throughout the construction process. Dynamic adjustment of construction parameters based on monitoring data. When the monitoring value reaches the early warning threshold, corresponding early warning response and disposal measures are initiated.

2. The method for micro-disturbance construction of subway shield tunneling combined with underground excavation through existing railway lines in anhydrous sand layers according to claim 1, characterized in that, In step S1, the measurement and layout and monitoring system setup deviation of the shield tunneling line is controlled within ±20mm, the measurement deviation of the cut-and-cover excavation outline is controlled within ±10mm, and the location deviation of the monitoring points is ≤5mm. The existing automated monitoring components include small prisms and hydrostatic levels.

3. The method for micro-disturbance construction of subway shield tunneling combined with underground excavation through existing railway lines in anhydrous sand layers according to claim 1, characterized in that, In the end reinforcement work of step S2, 2 rows of Φ800@1200mm C20 plain concrete piles are adopted, sleeve valve pipe grouting is carried out between the piles, the reinforcement range is 3m left and right and 3m longitudinally above and below the tunnel, after the reinforcement is completed, the unconfined compressive strength of the reinforced body is ≥0.5MPa, the permeability coefficient is <1.0×10 -6 cm / s, after reaching the standard, the subsequent portal breaking work can be carried out.

4. The method for micro-disturbance construction of subway shield tunneling combined with underground excavation through existing railway lines in anhydrous sand layers according to claim 1, characterized in that, In step S2 of the advanced support operation, the advanced small guide pipes are welded steel pipes with a diameter of 32×3.25mm and a length of 2m. They are laid out within a 150° range of the arch, with an installation angle of 30° and a circumferential spacing of 300mm. One ring is installed for each grid. Φ6~8mm overflow holes are drilled within 1m of the front end of the small guide pipes. Cement-water glass double liquid grout is used for grouting. The grouting pressure is controlled at 0.3~0.5MPa, and the grout diffusion radius is not less than 0.25m.

5. The method for micro-disturbance construction of subway shield tunneling combined with underground excavation through existing railway lines in anhydrous sand layers according to claim 1, characterized in that, In step S2, during the shield tunneling launch and trial excavation, the deviation between the center of the launch support and the tunnel design axis is controlled within ±10mm, and the end face of the reaction frame is perpendicular to the centerline of the support. During the shield tunneling launch stage, the tunneling parameters are controlled as follows: soil chamber pressure 1.0~1.4 bar, tunneling speed 5~10 mm / min, cutterhead speed 0.8~1.0 rpm. The installation and adjustment of the tunnel portal sealing device are completed simultaneously.

6. The method for micro-disturbance construction of subway shield tunneling combined with underground excavation through existing railway lines in anhydrous sand layers according to claim 1, characterized in that, During the shield tunneling construction in step S4, parameters such as soil chamber pressure, tunneling speed, and synchronous grouting volume are continuously adjusted based on surface settlement monitoring data.

7. The method for micro-disturbance construction of subway shield tunneling combined with underground excavation through existing railway lines in anhydrous sand layers according to claim 1, characterized in that, In step S4, during shield tunneling, when the shield tunnel crosses existing lines and risk sources, the soil chamber pressure is stably controlled at 1.0~1.4 bar with a fluctuation range of ≤±0.2 bar, the tunneling speed is stably controlled at 40~50 mm / min, and the tunneling is maintained at a uniform speed and continuous passage. The amount of excavated soil is controlled by volume and weight, with the amount of excavated soil per ring controlled at 46.1±2 m³. The horizontal attitude of the shield is controlled within ±20 mm, and the vertical attitude is controlled at ±20 mm at the front point and -30~-10 mm at the rear point. The amount of deviation correction in a single operation does not exceed 4 mm / m.

8. The method for micro-disturbance construction of subway shield tunneling combined with existing railway line crossing in anhydrous sand layers according to claim 7, characterized in that, During the shield tunneling construction in step S4, the grouting volume is increased to 1.2 times that of the ordinary section, 5.4 m³ / ring, and the grouting pressure is controlled at 2.0~4.0 bar. After the segments detach from the shield tail, secondary grouting is carried out. Secondary grouting is carried out every 3 rings when crossing the risk source section, and the grouting pressure is ≤0.5 MPa. When passing under a power tunnel, deep grouting is carried out through pre-reserved grouting holes after the segment detaches from the shield tail. The grouting pressure is controlled at 0.5~0.8MPa to supplement and reinforce the soil below the risk source.

9. The method for micro-disturbance construction of subway shield tunneling combined with underground excavation through existing railway lines in anhydrous sand layers according to claim 1, characterized in that, In step S5, during the construction of the tunnel entrance, welded steel pipes with a diameter of 32×3.25mm and a length of 3.5m are used for the advance guide pipes. They are arranged in a double-row, quincunx pattern along the 150° range of the outer contour arch of the tunnel entrance, with a circumferential spacing of 300mm and a grouting pressure of 0.3~0.5MPa. The retaining piles are removed manually using hand-held pneumatic picks. The removal sequence is from top to bottom and from the center to both sides, layer by layer. At the entrance, three grid steel frames are densely arranged with a spacing of 300mm. Double-layer Φ20 connecting bars are used to stagger the inner and outer sides. 300mm thick C25 concrete is sprayed to complete the support and closure.

10. The method for micro-disturbance construction of subway shield tunneling combined with underground excavation through existing railway lines in anhydrous sand layers according to claim 1, characterized in that, In step S6, during the excavation and support of the cut-and-cover tunnel, the excavation method is adapted to the tunnel cross-section dimensions. For the 6.5m QA / QD type cross-section, the upper and lower bench method with 2 pilot tunnels is used for excavation, with core soil reserved on the upper bench and the spacing between the upper and lower benches staggered by 5-10m. For the 9.4m QC type cross-section, the CRD method with 4 pilot tunnels is used for excavation, with each pilot tunnel staggered by 5-7m. For the 14.1m QB type cross-section, the double-side-wall pilot tunnel method with 9 pilot tunnels is used for excavation. Each pilot tunnel is constructed in a staggered manner according to the design sequence, and the excavation distance of the same numbered chambers on both sides is staggered by 8-10m.

Images