Full-face shield tunnel construction device and method for liquefied sand layer

Abstract

The application belongs to the technical field of shield tunnel construction, and discloses a full-face liquefied sand layer shield tunnel construction device and method, which comprises: an ultra-long distance shield axis positioning detection system, which is used for realizing real-time monitoring, deviation detection and positioning of the shield axis, and is composed of a ground pre-buried mechanism, a tunnel internal detection mechanism and a ground positioning mechanism; and a shield split starting extension pipeline protection system, which is composed of a support connecting mechanism, a pipeline placing groove and a drag reduction mechanism. Based on the above construction device, six construction steps of test section tunneling, phased test and parameter determination, axis positioning detection arrangement, pipeline protection, shield tunneling construction, pipeline extension and recovery are sequentially performed, so that efficient construction of the full-face liquefied sand layer shield tunnel is realized. The application adopts the above construction device and method, solves the core technical pain points in the construction of the full-face liquefied sand layer, improves the construction safety and efficiency, and is suitable for various full-face liquefied sand layer shield tunnel projects.

Description

Technical Field

[0001] This invention relates to the field of shield tunnel construction technology, and in particular to a shield tunnel construction device and method for a full-section liquefied sand layer. Background Technology

[0002] In the construction of infrastructure such as urban rail transit and river-crossing passages, shield tunneling is widely used due to its advantages such as high construction efficiency and minimal impact on the surrounding environment. However, when shield tunnels pass through liquefiable sand layers with a full cross-section, the construction process faces many technical challenges due to the high permeability, poor cohesion, weak stability, and sharp drop in strength after liquefaction of this stratum. These challenges severely restrict construction safety and efficiency.

[0003] The core challenges of full-face shield tunneling in liquefied sand layers are mainly reflected in three aspects: First, axis control is difficult. The significant difference in strength between the upper and lower strata of the liquefied sand layer leads to uneven shield advancement resistance, making it easy to encounter difficulties in advancement and failure of posture control. This can cause the shield axis to deviate from the design requirements, resulting in increased ground settlement and segment damage. Second, pipeline protection is poor. During the split-stage launch of the shield, various extension pipelines such as hydraulic pipes and cables are prone to haphazard stacking and mutual compression. During dragging, they are easily worn and damaged, which not only increases the cost of pipeline replacement and maintenance but also affects the efficiency of construction process connection. Third, ground settlement control is poor. The high porosity of the liquefied sand layer makes it difficult to fully fill the building voids generated by shield tunneling using conventional grouting methods. This can easily lead to problems such as water and sand inrush and excessive ground settlement, threatening the safety of surrounding buildings and underground pipelines.

[0004] Existing tunnel boring machine (TBM) construction technologies and equipment are mainly designed for ordinary strata. While they can meet the needs of conventional construction, they have significant limitations under the complex conditions of full-section liquefied sand layers: there is a lack of axis positioning and detection methods specifically adapted to liquefied sand layers, making it impossible to achieve accurate monitoring and real-time correction of the TBM axis; pipeline protection devices have simple structures and do not take into account the characteristics of frequent pipeline dragging and high wear risk during construction in liquefied sand layers, making it difficult to achieve orderly pipeline layout and effective protection; grouting parameter calculations have not been specifically modified in conjunction with the liquefaction characteristics of the sand layer, resulting in insufficient precision in controlling grouting volume and grouting pressure, and making it impossible to effectively control ground settlement.

[0005] Therefore, developing a construction method and device that is suitable for the working conditions of liquefied sand layers across the entire cross section and can systematically solve the above-mentioned technical pain points has become an urgent need in the field of shield tunnel construction. Summary of the Invention

[0006] The purpose of this invention is to provide a construction device and method for full-section liquefied sand layer shield tunnels. By optimizing the device structure design, improving the construction process, and establishing a dedicated grouting parameter calculation method, the invention achieves precise positioning of the shield axis, effective protection of pipelines, and precise control of ground settlement, thereby improving the safety, reliability, and construction efficiency of full-section liquefied sand layer shield tunnel construction and filling the gap in the existing technology in this field.

[0007] To achieve the above objectives, the present invention provides a shield tunnel construction device for a full-section liquefied sand layer, comprising two parts: an ultra-long distance shield axis positioning and detection system and a shield split launching extension pipeline protection system; The ultra-long-distance shield tunnel axis positioning and detection system is used to realize real-time monitoring, deviation detection and positioning of the shield tunnel axis. It consists of three parts: a ground pre-embedded mechanism, a tunnel detection mechanism and a ground positioning mechanism. The ground-embedded mechanism includes an inclinometer tube, which is buried in a pre-set hole above the underground tunnel. The burial depth is adapted to the tunnel depth to sense changes in the strata above the tunnel and vibrations caused by the tunnel boring machine's advance. A solid iron ball, a corner reflector, and a vibration probe are fixedly installed at the bottom of the inclinometer tube. The tunnel detection mechanism consists of a detection component and a ground-penetrating radar detection auxiliary component; the detection component is responsible for signal reception and geological detection, while the ground-penetrating radar detection auxiliary component is responsible for adjusting the position and height of the ground-penetrating radar. The ground positioning mechanism uses a total station, combined with positioning data from ground prisms and L-shaped prisms inside the tunnel, to achieve three-dimensional positioning of the shield tunnel axis, calculate the deviation between the shield tunnel axis and the design axis, and provide data support for axis correction. The shield tunneling split-type starting extension pipeline protection system consists of a support connection mechanism, a pipeline placement groove, and a drag reduction mechanism. Based on the type and specifications of the pipelines required for shield tunneling, multiple pipeline placement slots are set on the top and sides of the supporting connection mechanism. The size of each pipeline placement slot is adapted to the diameter of the corresponding pipeline, so as to realize the classified placement of various types of pipelines, ensure the orderly arrangement of pipelines, and facilitate the extension and recycling of pipelines. The drag reduction mechanism is installed on the pipeline placement trough to reduce resistance and wear during pipeline dragging. It uses one or a combination of pulley blocks and wear-resistant pads. The pulley blocks are installed on the inner wall of the pipeline placement trough and use wear-resistant rolling bearings, with the pipeline in contact with the pulley blocks. The wear-resistant pads are made of wear-resistant and corrosion-resistant materials and are laid on the bottom and side walls of the pipeline placement trough. To address the characteristics of liquefiable sand layers across the entire cross section, a calculation method for grouting volume and grouting pressure was designed. Furthermore, by introducing a sand layer porosity correction coefficient and a sand layer liquefaction correction pressure, the accuracy of parameter calculations was improved. (1) Calculate the grouting volume as follows: ; in, This refers to the grouting volume; This is the correction factor for the porosity of the sand layer; This is the slurry loss coefficient; The volume of the circumferential structure void during shield tunneling is shown below: ; in, The outer diameter of the tunnel boring machine; The outer diameter of the tunnel segment; For the width of the shield tunneling ring; (2) Calculate the grouting pressure as follows: ; in, This refers to the grouting pressure; This is the initial grouting pressure; The specific gravity of the slurry; Depth of the grouting point; Pressure correction for sand layer liquefaction.

[0008] Preferably, in the ground-embedded mechanism, a solid iron ball is used to increase the weight of the bottom of the inclinometer tube to ensure the stability of the inclinometer tube in the liquefied sand layer; a corner reflector is used to enhance the electromagnetic wave reflection signal and improve the transmission efficiency and receiving sensitivity of the electromagnetic wave signal; a vibration probe is used to sense the vibration of the liquefied sand layer in real time, and establishes a connection with the ground vibration frequency meter through a cable to transmit the vibration signal to the vibration frequency meter in real time, providing data support for axis deviation analysis.

[0009] Preferably, in the tunnel detection mechanism, the detection components include a ground-penetrating radar, an electromagnetic wave signal receiver, and a vibration frequency receiver. The ground-penetrating radar is used to detect the distribution, thickness, and stability of the liquefied sand layer in front of the tunnel face in real time, and to predict geological risks in advance. The electromagnetic wave signal receiver and the vibration frequency receiver are fixedly installed on the upper inner wall of the tunnel and kept parallel to the tunnel axis. The electromagnetic wave signal receiver is wirelessly connected to an electromagnetic wave signal transmitter on the ground cable and is used to receive electromagnetic wave signals reflected by corner reflectors in the ground-embedded mechanism to realize signal linkage between the ground and the tunnel. The vibration frequency receiver is used to receive the vibration frequency signal transmitted by the vibration probe and compare it with the data of the vibration frequency meter to help determine the impact of the shield tunneling on the strata and the axis deviation. The ground-penetrating radar detection auxiliary component includes a movable support and a height adjustment element. The movable support is equipped with wear-resistant wheels at the bottom to adapt to the position adjustment requirements of the ground-penetrating radar during shield tunneling. The height adjustment element adopts a telescopic structure, and the ground-penetrating radar is fixedly installed on the height adjustment element. The height of the ground-penetrating radar is adjusted according to the height of the tunnel face and the geological detection requirements to ensure that the detection range covers the entire tunnel face.

[0010] Preferably, the ground positioning mechanism includes a prism, which is mounted at the center of the top of the pre-embedded inclinometer tube and is coaxial with the inclinometer tube; at the same time, an L-shaped prism is installed inside the tunnel and fixed at the center of the detection basket. The detection basket moves synchronously with the tunnel boring machine to ensure that the L-shaped prism can reflect the position of the tunnel boring machine in real time.

[0011] Preferably, the support connection mechanism adopts an arc-shaped structure that is perfectly adapted to the inner cavity shape of the shield tunnel segment, and is fixedly connected to the shield tunnel segment by high-strength bolts, with anti-slip pads installed at the connection points.

[0012] A construction method for a shield tunneling device for full-section liquefied sand layers includes the following steps: Step S1: Test section excavation; First, a section of the liquefied sand layer in the entire cross-section of the shield tunnel was selected as the test section. The length of the test section was determined based on the project scale and the complexity of the strata. Subsequently, the tunnel boring machine was started to excavate the test section. During the excavation process, the propulsion system, grouting system, and muck removal system of the tunnel boring machine were comprehensively and systematically inspected and tested. The focus was on testing the operational stability, parameter adjustment flexibility, and reliability of each system, and timely troubleshooting of equipment failures to ensure that each system operated normally. Meanwhile, through the test section excavation, the excavation characteristics of the liquefied sand layer were initially understood; Step S2: Phased experiments and parameter determination; Settlement monitoring equipment such as level and total station was used to detect the ground settlement data of the test section in real time. The correlation between grouting volume, grouting pressure and ground settlement was analyzed by settlement fitting calculation. Combined with the calculation method of grouting volume and grouting pressure with the introduction of sand layer porosity correction coefficient and sand layer liquefaction correction pressure, the optimal grouting parameters for the suitable stratum were determined to control ground settlement. Step S3: Axis positioning and detection setup; First, on the ground above the tunnel, according to the shield design axis, a pre-embedded hole is preset every 50 to 100 meters. The position of the pre-embedded hole is consistent with the tunnel axis to ensure detection accuracy. The pre-embedded holes are drilled using drilling equipment, and the hole depth is matched with the tunnel burial depth. The inclinometer tube is buried in the pre-embedded hole, ensuring that the inclinometer tube is vertical and stable. The solid iron ball, corner reflector and vibration probe at the bottom of the inclinometer tube are firmly installed. Subsequently, the installation and commissioning of the ground-embedded mechanism, the tunnel detection mechanism, and the ground positioning mechanism were completed, specifically including: (1) Connect the vibration probe to the ground vibration frequency meter via a cable and adjust the signal transmission stability; (2) Install the electromagnetic wave signal receiver and vibration frequency receiver on the upper inner wall of the tunnel, ensuring that the installation position is accurate and the fixation is firm. Debug the wireless connection between the electromagnetic wave signal receiver and the ground electromagnetic wave signal transmitter to ensure smooth signal transmission. (3) The ground prism is set up at the center of the top of the inclinometer tube, and the L-shaped prism inside the tunnel is fixed at the center of the detection basket. The positioning accuracy is adjusted by the total station to ensure that the three-dimensional positioning data of the shield axis can be accurately obtained. Step S4: Protection of the shield tunneling unit's launching pipeline; The support and connection mechanism of the shield tunnel segment starting extension pipeline protection system is fixedly connected to the shield tunnel segment with high-strength bolts. After the connection is completed, the stability of the device is checked. According to the pipeline type and specifications, various pipelines such as hydraulic pipes, cables, and grouting pipes are classified and placed into the corresponding pipeline placement slots. The drag reduction mechanism is used to reduce the resistance and wear during the pipeline dragging process. Step S5: Shield tunneling construction; The tunnel boring machine was started, and formal tunneling began according to the tunneling parameters determined in the test section. During the tunneling process, the various structures worked together, and the specific process is as follows: Step S51: Real-time detection of the distribution, thickness and stability of the liquefied sand layer in front of the tunnel face using ground penetrating radar. If geological anomalies are detected, adjust the tunnel boring machine's advance speed and thrust parameters in a timely manner. Step S52: Receive signals from the ground-embedded mechanism in real time using an electromagnetic wave signal receiver and a vibration frequency receiver. Combine the positioning data of the ground positioning mechanism and the L-shaped prism in the tunnel with the data processing system to calculate the deviation between the shield axis and the design axis. Set the axis deviation threshold to ±50mm. When the deviation exceeds this threshold, adjust the stroke difference and thrust distribution of the shield machine's propulsion jacks to correct the axis deviation and ensure that the shield axis always meets the design requirements. Step S53: Simultaneously, based on the grouting volume and grouting pressure parameters determined in step S2, synchronous grouting is carried out. During the grouting process, the grouting volume and grouting pressure are monitored in real time, and the parameters are adjusted in a timely manner to ensure that the grout fully fills the building voids generated by the shield tunneling and to control the ground settlement within the allowable range specified in the code. Step S6: Pipeline extension and recovery; During the tunnel boring machine (TBM) excavation, various pipelines need to be extended synchronously as the TBM advances. At this time, the pipelines are extended in an orderly manner along the pipeline placement trench by utilizing the classified arrangement of the pipeline placement trench and the drag reduction mechanism. After the construction is completed, the various pipelines are retrieved in reverse along the pipeline placement trench. During the retrieval process, the pipelines are checked for wear and damage. Damaged pipelines are repaired or replaced to complete the entire TBM tunnel construction process.

[0013] Therefore, the present invention employs the above-mentioned full-section liquefied sand layer shield tunnel construction device and method, and the beneficial effects are as follows: (1) High accuracy of axis control: In view of the working conditions of the full-section liquefied sand layer, the ultra-long distance shield axis positioning and detection system is designed. Combined with ground penetrating radar, electromagnetic wave signal, vibration signal detection and prism three-dimensional positioning, it realizes real-time monitoring and accurate correction of the shield axis, and controls the axis deviation within ±50mm. It solves the technical pain points of difficult axis control and excessive deviation in the existing technology, and effectively avoids the hidden dangers such as ground settlement aggravation and segment damage caused by axis deviation.

[0014] (2) Good pipeline protection effect: The shield tunneling split launch extension pipeline protection system realizes the orderly arrangement of pipelines through classified placement slots, and reduces pipeline drag resistance and wear by combining drag reduction mechanism, avoiding pipeline mess, entanglement and damage, reducing pipeline replacement and maintenance costs, and reducing the workload of pipeline extension and recovery, improving construction efficiency by more than 20%, and solving the problem of pipeline protection during shield tunneling split launch.

[0015] (3) Precise ground settlement control: The proposed grouting volume and grouting pressure calculation method is specifically modified for the characteristics of the full-section liquefied sand layer. By introducing the sand layer porosity correction coefficient and sand layer liquefaction correction pressure, the calculation accuracy of grouting parameters is improved. Combined with the synchronous grouting process, it can effectively fill the building voids and control the ground settlement within the allowable range of the standard. It solves the problems of excessive ground settlement, water inrush and sand inrush caused by liquefaction of silty sand layer, and ensures the safety of surrounding buildings and underground pipelines.

[0016] (4) High construction safety and efficiency: The construction method and equipment are used in combination, which systematically solves the core technical problems such as axis control, pipeline protection and ground settlement control in the construction of shield tunnels in full-section liquefied sand layers. It optimizes the construction process, reduces construction hazards and downtime due to malfunctions, improves the safety and reliability of construction, and reduces construction costs. It is applicable to various full-section liquefied sand layer shield tunnel projects and has a wide range of application prospects.

[0017] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a shield tunnel construction device for a full-section liquefied sand layer according to the present invention; Figure 2 This is a flowchart of a shield tunnel construction method for a full-section liquefied sand layer according to the present invention. Detailed Implementation

[0019] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] like Figure 1As shown, the present invention provides a full-section shield tunnel construction device for liquefied sand layers, which mainly consists of two parts: an ultra-long-distance shield axis positioning and detection system and a shield split starting extension pipeline protection system. The two parts are independent of each other and work together to solve the two core problems of axis control and pipeline protection, respectively, while providing support for ground settlement control.

[0021] I. Ultra-long distance shield tunnel axis positioning and detection system, used to realize real-time monitoring, deviation detection and precise positioning of shield tunnel axis, adapted to the unstable strata of liquefied sand layer and easy axis deviation in the whole section, and consists of three parts: ground pre-embedded mechanism, tunnel detection mechanism and ground positioning mechanism.

[0022] 1. Ground-embedded mechanism: The core component is the inclinometer tube, which is made of high-strength, wear-resistant pipe and buried in pre-set holes above the underground tunnel. The burial depth is adapted to the tunnel depth to ensure accurate detection of changes in the strata above the tunnel and vibrations caused by the tunnel boring machine's (TBM) advancement. A solid iron ball, corner reflector, and vibration probe are fixedly installed at the bottom of the inclinometer tube. The solid iron ball increases the weight at the bottom of the inclinometer tube, ensuring its stability in the liquefied sand layer and preventing displacement due to strata liquefaction, which would affect detection accuracy. The corner reflector enhances the reflected electromagnetic wave signal, improving the transmission efficiency and receiving sensitivity of the electromagnetic wave signal, facilitating accurate signal capture by the detection device inside the tunnel. The vibration probe is used to sense the vibration of the liquefied sand layer in real time. It is connected to a ground-based vibration frequency meter via a cable, transmitting the vibration signal to the meter in real time to provide data support for axis deviation analysis.

[0023] 2. Tunnel Detection Mechanism: It consists of a detection component and a ground-penetrating radar detection auxiliary component. The detection component is responsible for signal reception and stratum detection, while the ground-penetrating radar detection auxiliary component is responsible for adjusting the position and height of the ground-penetrating radar to ensure detection effectiveness.

[0024] The detection components include a ground-penetrating radar, an electromagnetic wave signal receiver, and a vibration frequency receiver. The ground-penetrating radar is used to detect the distribution, thickness, and stability of the liquefied sand layer in front of the tunnel face in real time, predict geological risks in advance, and provide a basis for adjusting the tunnel boring machine (TBM) propulsion parameters. The electromagnetic wave signal receiver and the vibration frequency receiver are fixedly installed on the upper inner wall of the tunnel and kept parallel to the tunnel axis. The electromagnetic wave signal receiver is wirelessly connected to an electromagnetic wave signal transmitter on the ground cable to receive electromagnetic wave signals reflected by corner reflectors in the ground-embedded mechanism, realizing signal linkage between the ground and the tunnel. The vibration frequency receiver is used to receive the vibration frequency signal transmitted by the vibration probe and compare it with the data of the vibration frequency meter to help determine the impact of the TBM propulsion on the strata and the axis deviation.

[0025] The ground-penetrating radar (GPR) detection auxiliary component includes a movable support and a height adjustment element. The movable support is equipped with wear-resistant wheels at the bottom for easy movement within the tunnel, adapting to the position adjustment requirements of the GPR during shield tunneling. The height adjustment element adopts a telescopic structure, with the GPR fixedly mounted on it. The height of the GPR can be flexibly adjusted according to the tunnel face height and geological detection requirements to ensure that the detection range covers the entire tunnel face and improve detection accuracy.

[0026] 3. Ground Positioning Mechanism: The core component is a prism, which is mounted at the center of the top of the pre-embedded inclinometer tube, maintaining coaxiality with the tube to ensure the accuracy of the positioning benchmark. Simultaneously, an L-shaped prism is installed inside the tunnel, fixed at the center of the detection basket. The detection basket moves synchronously with the tunnel boring machine (TBM), ensuring the L-shaped prism reflects the TBM's position in real time. The ground positioning mechanism, using equipment such as a total station, combines positioning data from the ground prism and the L-shaped prism inside the tunnel to achieve three-dimensional positioning of the TBM's axis, accurately calculating the deviation between the TBM's axis and the design axis, providing data support for axis correction.

[0027] II. Shield Tunnel Split Launch Extension Pipeline Protection System: This system is designed to address issues such as messy pipelines, severe wear, and inconvenience in extension and recovery during the shield tunnel split launch process. It consists of a support connection mechanism, multiple pipeline placement slots, and a drag reduction mechanism.

[0028] 1. Support and Connection Mechanism: The support and connection mechanism adopts an arc-shaped structure that perfectly matches the inner shape of the tunnel segment. High-strength steel is used to ensure structural strength and stability. The support and connection mechanism is fixed to the tunnel segment using high-strength bolts. Anti-slip pads are installed at the connection points to prevent loosening due to tunnel vibration during construction, providing a stable installation foundation for pipeline protection.

[0029] 2. Pipeline placement slots: Based on the type and specifications of pipelines required for shield tunneling, multiple pipeline placement slots are set on the top and sides of the support connection mechanism in different categories. The size of each pipeline placement slot is adapted to the diameter of the corresponding pipeline, which can realize the classified placement of various pipelines such as hydraulic pipes, cables, and grouting pipes, avoid pipelines squeezing or tangling with each other, ensure orderly pipeline layout, and facilitate pipeline extension and recovery.

[0030] 3. Drag Reduction Mechanism: Installed on the pipeline placement trench, this mechanism reduces resistance and wear during pipeline dragging, extends pipeline lifespan, and reduces construction workload. It can be composed of one or a combination of pulley blocks and wear-resistant pads. The pulley blocks, installed on the inner wall of the pipeline placement trench, utilize wear-resistant rolling bearings. The contact between the pipeline and the pulley blocks converts sliding friction into rolling friction, significantly reducing dragging resistance. The wear-resistant pads, made of wear-resistant and corrosion-resistant materials such as polyurethane, are laid on the bottom and side walls of the pipeline placement trench, reducing wear between the pipeline and the trench while also acting as a buffer to prevent pipeline damage due to vibration.

[0031] like Figure 2 As shown, the present invention discloses a method for constructing a full-section liquefied sand layer shield tunnel. Based on the above-mentioned construction device, and following the principles of trial first, precise control, and coordinated construction, the method proceeds through six steps in sequence: test section excavation, phased testing and parameter determination, axis positioning and detection layout, pipeline protection, shield tunneling construction, and pipeline extension and recovery. This method enables the safe and efficient construction of a full-section liquefied sand layer shield tunnel.

[0032] Step S1: Test section excavation.

[0033] A section within the liquefied sand layer of the entire shield tunnel is selected as a test section. The length of the test section is determined based on the project scale and geological complexity, generally ranging from 100 to 200 meters. The shield machine is then started to excavate the test section. During excavation, a comprehensive and systematic inspection and testing of all functional systems of the shield machine, including its propulsion system, grouting system, and muck removal system, is conducted. The focus is on testing the operational stability, parameter adjustment flexibility, and reliability of each system, promptly identifying and troubleshooting equipment malfunctions, and ensuring the normal and effective operation of each system to provide reliable equipment support for subsequent formal construction. Simultaneously, the test section excavation provides a preliminary understanding of the excavation characteristics of the liquefied sand layer, providing fundamental data for subsequent phased tests and parameter determination.

[0034] Step S2: Phased experiments and parameter determination.

[0035] Based on the characteristics of the liquefied sand layer in the next stage of shield tunneling (such as porosity, liquefaction degree, and burial depth), phased tests of construction measures will be conducted in the test section, focusing on grouting tests and axis control tests. Settlement monitoring equipment such as levels and total stations will be used to monitor ground settlement data in the test section in real time. Through settlement fitting calculations, the correlation between grouting volume, grouting pressure, and ground settlement will be analyzed. Combined with the invention's proprietary calculation methods for grouting volume and pressure, the optimal grouting parameters suitable for this stratum will be determined to ensure that the grouting effectively fills the structural voids generated by shield tunneling and controls ground settlement.

[0036] Specifically, a calculation method for grouting volume and grouting pressure was designed for the characteristics of the full-section liquefiable sand layer. The accuracy of parameter calculation was improved by introducing a sand layer porosity correction coefficient and a sand layer liquefaction correction pressure.

[0037] (1) Calculate the grouting volume as follows: ; in, Grouting volume (m) 3 ); This is a porosity correction factor for the sand layer, with a value ranging from 1.2 to 1.5. It is adjusted according to the porosity of the liquefied sand layer; the higher the porosity, the better. The larger the value; This is the slurry loss coefficient, with a value ranging from 0.1 to 0.3. It is adjusted according to the degree of sand liquefaction; the higher the degree of liquefaction, the greater the slurry loss. The larger the value; The circumferential void volume of the shield tunneling structure (m³) 3 ), as shown below: ; in, The outer diameter of the shield tunnel (m); The outer diameter of the tunnel segment (m); The width of the tunnel boring machine's excavation ring (m).

[0038] (2) Calculate the grouting pressure as follows: ; in, Grouting pressure (MPa); The initial grouting pressure is 0.1~0.2MPa, used to start the grouting system and ensure smooth injection of grout. The specific gravity of the slurry (kN / m) 3 The value is 18~20kN / m 3 Adjust according to the slurry ratio; The grouting point depth (m) is the vertical distance from the grouting point to the ground surface. The correction pressure for sand liquefaction is 0.05~0.1MPa. It is used to compensate for insufficient strength of liquefied sand layers, ensure that the grout can fully fill the voids in the structure, and avoid problems such as grout loss and poor grouting effect.

[0039] Step S3: Axis positioning and detection setup.

[0040] First, on the ground above the tunnel, pre-embedded holes are pre-set every 50-100 meters according to the shield tunneling design axis. The positions of the pre-embedded holes are consistent with the tunnel axis to ensure detection accuracy. Pre-embedded holes are drilled using drilling equipment, with the hole depth matching the tunnel depth. The inclinometer tube is then slowly embedded into the pre-embedded hole, ensuring the inclinometer tube is vertical and stable, and that the solid iron ball, corner reflector, and vibration probe at the bottom of the inclinometer tube are securely installed.

[0041] Subsequently, the installation and commissioning of the ground-embedded mechanism, the tunnel detection mechanism, and the ground positioning mechanism were completed, specifically including: (1) Connect the vibration probe to the ground vibration frequency meter via a cable and adjust the signal transmission stability; (2) Install the electromagnetic wave signal receiver and vibration frequency receiver on the upper inner wall of the tunnel, ensuring that the installation position is accurate and the fixation is firm. Debug the wireless connection between the electromagnetic wave signal receiver and the ground electromagnetic wave signal transmitter to ensure smooth signal transmission. (3) The ground prism is set up at the center of the top of the inclinometer tube, and the L-shaped prism inside the tunnel is fixed at the center of the detection basket. The positioning accuracy is adjusted by the total station to ensure that the three-dimensional positioning data of the shield axis can be accurately obtained.

[0042] Step S4: Protection of the shield tunneling unit's starting pipeline.

[0043] The support and connection mechanism of the shield tunnel segment originating extension pipeline protection system is fixedly connected to the shield tunnel segments using high-strength bolts. After connection, the stability of the device is checked to ensure there is no loosening. According to pipeline type and specifications, various pipelines such as hydraulic pipes, cables, and grouting pipes are classified and placed into their corresponding pipeline placement slots, ensuring the pipelines are neatly arranged, without tangling or compression. If the drag reduction mechanism uses a combination of pulley blocks and wear-resistant pads, it is necessary to ensure that the pulley blocks are installed flexibly without jamming, and that the wear-resistant pads are laid flat and undamaged. The drag reduction mechanism reduces resistance and wear during pipeline dragging, preparing for subsequent pipeline extension.

[0044] Step S5: Shield tunneling construction.

[0045] The tunnel boring machine was started, and formal tunneling began according to the tunneling parameters determined in the test section. During the tunneling process, the various structures worked together to achieve precise control. The specific process is as follows: Step S51: Real-time detection of the distribution, thickness and stability of the liquefied sand layer in front of the tunnel face using ground penetrating radar. If geological anomalies are found (such as increased sand liquefaction, presence of weak interlayers, etc.), adjust the shield tunneling speed, thrust and other parameters in a timely manner to avoid potential hazards such as water inrush, sand inrush, and tunnel face collapse. Step S52: Receive signals from the ground-embedded mechanism in real time using an electromagnetic wave signal receiver and a vibration frequency receiver. Combine the positioning data of the ground positioning mechanism and the L-shaped prism in the tunnel with the data processing system to calculate the deviation between the shield axis and the design axis. Set the axis deviation threshold to ±50mm. When the deviation exceeds this threshold, adjust the stroke difference and thrust distribution of the shield machine's propulsion jacks to correct the axis deviation and ensure that the shield axis always meets the design requirements. Step S53: Simultaneously, based on the grouting volume and grouting pressure parameters determined in step S2, synchronous grouting is carried out. During the grouting process, the grouting volume and grouting pressure are monitored in real time, and the parameters are adjusted in a timely manner to ensure that the grout fully fills the building voids generated by the shield tunneling, effectively control ground settlement, and keep the ground settlement within the allowable range specified in the standard.

[0046] Step S6: Pipeline extension and recovery.

[0047] During the tunnel boring machine (TBM) excavation, various pipelines need to be extended synchronously as the TBM advances. At this time, the pipeline placement trenches are used to extend the pipelines in an orderly manner, avoiding mess and entanglement, and reducing drag resistance and wear. After construction is completed, in accordance with the principle of "classified recycling and orderly sorting", the various pipelines are recycled in reverse along the pipeline placement trenches. During the recycling process, the pipelines are checked for wear and damage. Damaged pipelines are repaired or replaced to facilitate subsequent reuse, thus completing the entire TBM tunnel construction process.

[0048] Example 1 This embodiment is applied to a subway tunnel project in a city. The project passes through a full-section liquefiable sand layer with a porosity of 35%~40% and a moderate degree of liquefaction. The tunnel is 18m deep, the shield outer diameter D is 6.2m, the segment outer diameter d is 6.0m, and the shield excavation ring width L is 1.5m. During construction, it is necessary to focus on controlling the axial deviation and ground settlement, while also ensuring the protection of pipelines.

[0049] 1. System setup and debugging.

[0050] (1) Ultra-long distance shield axis positioning and detection system: A pre-embedded hole is set every 50m on the ground above the tunnel. A pre-embedded hole with a diameter of 160mm and a depth of 20m is drilled using drilling equipment. A high-strength inclinometer tube with a diameter of 150mm is buried in the hole. A solid iron ball, corner reflector and vibration probe are installed at the bottom of the inclinometer tube. The vibration probe is connected to the ground vibration frequency meter through a cable. An electromagnetic wave signal receiver and a vibration frequency receiver are installed on the upper inner wall of the tunnel, which are kept parallel to the tunnel axis. The ground penetrating radar is installed on a movable support with a height adjustment component. The bottom of the movable support is equipped with wear-resistant walking wheels. The prism of the ground positioning device is set at the center of the top of the inclinometer tube. The L-shaped prism inside the tunnel is fixed at the center of the detection basket. After debugging with a total station, the positioning accuracy reaches ±5mm.

[0051] (2) Shield tunnel segment starting extension pipeline protection system: an arc-shaped support connection mechanism adapted to the inner cavity of the shield tunnel segment is made of high-strength steel and fixed to the shield tunnel segment by high-strength bolts. Anti-slip pads are set at the connection parts. Three hydraulic pipe placement grooves (diameter 80mm) and two cable placement grooves (diameter 50mm) are set at the top of the support connection mechanism. Pulley groups are installed on the inner wall of the placement grooves. The bottom and side walls of the grooves are covered with polyurethane wear-resistant pads with a thickness of 10mm.

[0052] 2. Construction process.

[0053] (1) Test section tunneling: A 100m test section was selected for tunneling. The propulsion system, grouting system and slag removal system of the shield machine were fully tested. All systems were operating normally, and the tunneling characteristics of the liquefied sand layer were initially understood.

[0054] (2) Phased tests and parameter determination: Phased grouting tests were conducted, and ground settlement data were monitored in real time using a level. Based on the grouting volume and grouting pressure calculation method of this invention, the parameters were determined as follows: Sand layer porosity correction factor Take 1.3 as the slurry loss coefficient. Take 0.2; the circumferential void volume of the shield tunneling structure is: Grouting volume is: ; Grouting point burial depth Initial grouting pressure Take 0.15 MPa, slurry unit weight Take 19kN / m 3 Sand layer liquefaction correction pressure If we take 0.08 MPa, then the grouting pressure is... .

[0055] (3) Axis positioning detection setup: The installation and debugging of each detection device were completed. The electromagnetic wave signal receiver and the ground electromagnetic wave signal transmitter were wirelessly connected smoothly. The vibration probe and the vibration frequency meter transmitted signals normally. The positioning accuracy of the total station met the requirements.

[0056] (4) Protection of the shield tunneling unit's starting pipeline: Place the hydraulic pipes and cables into their respective placement slots, and use pulley blocks and wear-resistant pads for protection to ensure that the pipelines are neatly arranged and free from tangling.

[0057] (5) Tunneling construction: The tunnel boring machine was started and tunneling was carried out. The advance speed was controlled at 30 mm / min. The ground penetrating radar detected the strata in front of the tunnel face in real time and no abnormalities were found. The axis positioning detection device detected an axis deviation of 60 mm, which exceeded the threshold of ±50 mm. By adjusting the stroke difference of the advance jack, the axis deviation was corrected to 40 mm, which met the requirements. Synchronous grouting was carried out according to the calculated grouting volume and pressure. The ground settlement monitoring data showed that the maximum settlement was 30 mm, which met the specifications.

[0058] (6) Pipeline extension and recovery: During the tunnel boring process, the pipeline is extended in an orderly manner along the placement trench, and the dragging resistance is significantly reduced; after the construction is completed, the pipeline is recovered along the placement trench, and there is no pipeline wear or damage.

[0059] Example 2 This embodiment is applied to a river-crossing tunnel project. The project passes through a full-section liquefied sand layer with a porosity of 40%~45% and a high degree of liquefaction. The tunnel is 30m deep, the shield outer diameter D is 11.3m, the segment outer diameter d is 11.0m, and the ring width L is 2.0m. The construction is difficult and the requirements for axis control and ground settlement control are strict.

[0060] 1. Equipment setup and debugging.

[0061] (1) Ultra-long distance shield axis positioning and detection system: a pre-embedded hole is set every 80m above the tunnel. A pre-embedded hole with a diameter of 200mm and a depth of 32m is drilled and a 180mm diameter inclinometer tube is buried. A solid iron ball, corner reflector and vibration probe are installed at the bottom of the inclinometer tube. The vibration probe is connected to the ground vibration frequency meter through a cable. An electromagnetic wave signal receiver and a vibration frequency receiver are installed in the tunnel. The ground penetrating radar is installed on a movable support with a height adjustment range of 1.5~3.0m. The ground prism and the L-shaped prism in the tunnel are installed and debugged, and the positioning accuracy reaches ±5mm.

[0062] (2) Shield tunneling segment starting extension pipeline protection system: The support connection mechanism adopts an arc structure, which is adapted to the inner cavity of the shield tunnel segment and is fixed by high-strength bolts. Four hydraulic pipe placement slots, three cable placement slots, and two grouting pipe placement slots are respectively set on the top and side of the support connection mechanism. The inner wall of the placement slot is equipped with pulley blocks, and the bottom and side walls of the slot are covered with a polyurethane wear-resistant pad with a thickness of 12mm.

[0063] 2. Construction process.

[0064] (1) Test section tunneling: A 150m test section was selected for tunneling. The various functional systems of the tunnel boring machine were tested to ensure normal operation and to understand the tunneling characteristics of the high liquefaction sand layer.

[0065] (2) Phased tests and parameter determination: Phased grouting tests were conducted, and the parameters were determined as follows: Sand layer porosity correction factor Take 1.4 as the slurry loss coefficient. Take 0.25; the circumferential void volume of the shield tunneling structure is: Grouting volume is: ; Grouting point burial depth Initial grouting pressure Take 0.2 MPa, slurry unit weight Take 20kN / m 3 Sand layer liquefaction correction pressure Take 0.1 MPa as the grouting pressure. .

[0066] (3) Axis positioning and detection layout: After the installation and debugging of each device are completed, the signal transmission is smooth and the positioning is accurate.

[0067] (4) Protection of the starting pipeline of the shield tunnel: Classify and place various pipelines into the corresponding placement slots, and use the drag reduction mechanism to protect them.

[0068] (5) Shield tunneling construction: The shield machine advance speed is controlled at 25mm / min, the ground penetrating radar detects the strata in real time, and avoids the risk of strata anomalies in a timely manner; the axis deviation is always controlled within ±45mm, the synchronous grouting effect is good, and the maximum ground settlement is 25mm, which meets the requirements of the specifications.

[0069] (6) Pipeline extension and recycling: There is no wear during pipeline extension and the pipeline can be successfully recycled after construction, improving construction efficiency by 25%.

[0070] Therefore, the present invention adopts the above-mentioned construction device and method for full-section liquefied sand layer shield tunnels. The construction device and method work together to systematically solve the core technical pain points in the construction of full-section liquefied sand layers, and improve construction safety and efficiency. The construction method is based on the construction device and combined with the calculation method of grouting volume and grouting pressure to achieve precise control of the shield axis, effective protection of pipelines and precise control of ground settlement. It is applicable to various full-section liquefied sand layer shield tunnel projects.

[0071] Finally, 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 still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A shield tunnel construction device for full-section liquefied sand layers, characterized in that: It consists of two parts: an ultra-long-distance shield tunnel axis positioning and detection system and a shield tunnel split-type starting and extension pipeline protection system; The ultra-long-distance shield tunnel axis positioning and detection system is used to realize real-time monitoring, deviation detection and positioning of the shield tunnel axis. It consists of three parts: a ground pre-embedded mechanism, a tunnel detection mechanism and a ground positioning mechanism. The ground-embedded mechanism includes an inclinometer tube, which is buried in a pre-set hole above the underground tunnel. The burial depth is adapted to the tunnel depth to sense changes in the strata above the tunnel and vibrations caused by the tunnel boring machine's advance. A solid iron ball, a corner reflector, and a vibration probe are fixedly installed at the bottom of the inclinometer tube. The tunnel detection mechanism consists of a detection component and a ground-penetrating radar detection auxiliary component; the detection component is responsible for signal reception and geological detection, while the ground-penetrating radar detection auxiliary component is responsible for adjusting the position and height of the ground-penetrating radar. The ground positioning mechanism uses a total station, combined with positioning data from ground prisms and L-shaped prisms inside the tunnel, to achieve three-dimensional positioning of the shield tunnel axis, calculate the deviation between the shield tunnel axis and the design axis, and provide data support for axis correction. The shield tunneling split-type starting extension pipeline protection system consists of a support connection mechanism, a pipeline placement groove, and a drag reduction mechanism. Based on the type and specifications of the pipelines required for shield tunneling, multiple pipeline placement slots are set on the top and sides of the supporting connection mechanism. The size of each pipeline placement slot is adapted to the diameter of the corresponding pipeline, so as to realize the classified placement of various types of pipelines, ensure the orderly arrangement of pipelines, and facilitate the extension and recycling of pipelines. The drag reduction mechanism is installed on the pipeline placement trough to reduce resistance and wear during pipeline dragging. It uses one or a combination of pulley blocks and wear-resistant pads. The pulley blocks are installed on the inner wall of the pipeline placement trough and use wear-resistant rolling bearings, with the pipeline in contact with the pulley blocks. The wear-resistant pads are made of wear-resistant and corrosion-resistant materials and are laid on the bottom and side walls of the pipeline placement trough. To address the characteristics of liquefiable sand layers across the entire cross section, a calculation method for grouting volume and grouting pressure was designed. Furthermore, by introducing a sand layer porosity correction coefficient and a sand layer liquefaction correction pressure, the accuracy of parameter calculations was improved. (1) Calculate the grouting volume as follows: ； in, This refers to the grouting volume; This is the correction factor for the porosity of the sand layer; This is the slurry loss coefficient; The volume of the circumferential structure void during shield tunneling is shown below: ； in, The outer diameter of the tunnel boring machine; The outer diameter of the tunnel segment; For the width of the shield tunneling ring; (2) Calculate the grouting pressure as follows: ； in, This refers to the grouting pressure. This is the initial grouting pressure; The specific gravity of the slurry; Depth of the grouting point; Pressure correction for sand layer liquefaction.

2. The shield tunnel construction device for full-section liquefied sand layer according to claim 1, characterized in that: In the ground-embedded mechanism, solid iron balls are used to increase the weight of the bottom of the inclinometer tube, ensuring the stability of the inclinometer tube in the liquefied sand layer; corner reflectors are used to enhance the electromagnetic wave reflection signal, improve the transmission efficiency and receiving sensitivity of the electromagnetic wave signal; vibration probes are used to sense the vibration of the liquefied sand layer in real time, and are connected to the ground vibration frequency meter through a cable to transmit the vibration signal to the vibration frequency meter in real time, providing data support for axis deviation analysis.

3. The shield tunnel construction device for full-section liquefied sand layer according to claim 1, characterized in that: The detection mechanism inside the tunnel includes a ground-penetrating radar, an electromagnetic wave signal receiver, and a vibration frequency receiver. The ground-penetrating radar is used to detect the distribution, thickness, and stability of the liquefied sand layer in front of the tunnel face in real time, and to predict geological risks in advance. The electromagnetic wave signal receiver and the vibration frequency receiver are fixedly installed on the upper inner wall of the tunnel and kept parallel to the tunnel axis. The electromagnetic wave signal receiver is wirelessly connected to the electromagnetic wave signal transmitter on the ground cable and is used to receive the electromagnetic wave signal reflected by the corner reflector in the ground pre-embedded mechanism to realize the signal linkage between the ground and the tunnel. The vibration frequency receiver is used to receive the vibration frequency signal transmitted by the vibration probe and compare it with the data of the vibration frequency meter to help judge the impact of the shield tunneling on the strata and the axis deviation. The ground-penetrating radar detection auxiliary component includes a movable support and a height adjustment element. The movable support is equipped with wear-resistant wheels at the bottom to adapt to the position adjustment requirements of the ground-penetrating radar during shield tunneling. The height adjustment element adopts a telescopic structure, and the ground-penetrating radar is fixedly installed on the height adjustment element. The height of the ground-penetrating radar is adjusted according to the height of the tunnel face and the geological detection requirements to ensure that the detection range covers the entire tunnel face.

4. The shield tunnel construction device for full-section liquefied sand layer according to claim 1, characterized in that: The ground positioning mechanism includes a prism, which is mounted at the center of the top of the pre-embedded inclinometer tube and is coaxial with the inclinometer tube. At the same time, an L-shaped prism is installed inside the tunnel and fixed at the center of the detection basket. The detection basket moves synchronously with the tunnel boring machine to ensure that the L-shaped prism can reflect the position of the tunnel boring machine in real time.

5. The shield tunnel construction device for full-section liquefied sand layer according to claim 1, characterized in that: The support connection mechanism adopts an arc-shaped structure that is perfectly adapted to the inner cavity shape of the shield tunnel segment. It is fixedly connected to the shield tunnel segment by high-strength bolts, and anti-slip pads are installed at the connection points.

6. A construction method for a full-section liquefied sand layer shield tunnel construction device according to any one of claims 1-5, characterized in that, Includes the following steps: Step S1: Test section excavation; First, a section of the liquefied sand layer in the entire cross-section of the shield tunnel was selected as the test section. The length of the test section was determined based on the project scale and the complexity of the strata. Subsequently, the tunnel boring machine was started to excavate the test section. During the excavation process, the propulsion system, grouting system, and muck removal system of the tunnel boring machine were comprehensively and systematically inspected and tested. The focus was on testing the operational stability, parameter adjustment flexibility, and reliability of each system, and timely troubleshooting of equipment failures to ensure that each system operated normally. Meanwhile, through the test section excavation, the excavation characteristics of the liquefied sand layer were initially understood; Step S2: Phased experiments and parameter determination; Settlement monitoring equipment such as level and total station was used to detect the ground settlement data of the test section in real time. The correlation between grouting volume, grouting pressure and ground settlement was analyzed by settlement fitting calculation. Combined with the calculation method of grouting volume and grouting pressure with the introduction of sand layer porosity correction coefficient and sand layer liquefaction correction pressure, the optimal grouting parameters for the suitable stratum were determined to control ground settlement. Step S3: Axis positioning and detection setup; First, on the ground above the tunnel, according to the shield design axis, a pre-embedded hole is pre-set every 50 to 100 meters. The position of the pre-embedded hole is consistent with the tunnel axis to ensure detection accuracy. Pre-embedded holes are drilled using drilling equipment, with the hole depth matching the tunnel burial depth. Inclinometer tubes are then embedded in the pre-embedded holes to ensure that the inclinometer tubes are vertical and stable. The solid iron ball, corner reflector, and vibration probe at the bottom of the inclinometer tubes are securely installed. Subsequently, the installation and commissioning of the ground-embedded mechanism, the tunnel detection mechanism, and the ground positioning mechanism were completed, specifically including: (1) Connect the vibration probe to the ground vibration frequency meter via a cable and adjust the signal transmission stability; (2) Install the electromagnetic wave signal receiver and vibration frequency receiver on the upper inner wall of the tunnel, ensuring that the installation position is accurate and the fixation is firm. Debug the wireless connection between the electromagnetic wave signal receiver and the ground electromagnetic wave signal transmitter to ensure smooth signal transmission. (3) The ground prism is set up at the center of the top of the inclinometer tube, and the L-shaped prism inside the tunnel is fixed at the center of the detection basket. The positioning accuracy is adjusted by the total station to ensure that the three-dimensional positioning data of the shield axis can be accurately obtained. Step S4: Protection of the shield tunneling unit's launching pipeline; The support and connection mechanism of the shield tunnel segment starting extension pipeline protection system is fixedly connected to the shield tunnel segment with high-strength bolts. After the connection is completed, the stability of the device is checked. According to the pipeline type and specifications, various pipelines such as hydraulic pipes, cables, and grouting pipes are classified and placed into the corresponding pipeline placement slots. The drag reduction mechanism is used to reduce the resistance and wear during the pipeline dragging process. Step S5: Shield tunneling construction; The tunnel boring machine was started, and formal tunneling began according to the tunneling parameters determined in the test section. During the tunneling process, the various structures worked together, and the specific process is as follows: Step S51: Real-time detection of the distribution, thickness and stability of the liquefied sand layer in front of the tunnel face using ground penetrating radar. If geological anomalies are detected, adjust the tunnel boring machine's advance speed and thrust parameters in a timely manner. Step S52: Receive signals from the ground-embedded mechanism in real time using an electromagnetic wave signal receiver and a vibration frequency receiver. Combine the positioning data of the ground positioning mechanism and the L-shaped prism in the tunnel with the data processing system to calculate the deviation between the shield axis and the design axis. Set the axis deviation threshold to ±50mm. When the deviation exceeds this threshold, adjust the stroke difference and thrust distribution of the shield machine's propulsion jacks to correct the axis deviation and ensure that the shield axis always meets the design requirements. Step S53: Simultaneously, based on the grouting volume and grouting pressure parameters determined in step S2, synchronous grouting is carried out. During the grouting process, the grouting volume and grouting pressure are monitored in real time, and the parameters are adjusted in a timely manner to ensure that the grout fully fills the building voids generated by the shield tunneling and to control the ground settlement within the allowable range specified in the code. Step S6: Pipeline extension and recovery; During the tunnel boring machine (TBM) excavation, various pipelines need to be extended synchronously as the TBM advances. At this time, the pipelines are extended in an orderly manner along the pipeline placement trench by utilizing the classified arrangement of the pipeline placement trench and the drag reduction mechanism. After the construction is completed, the various pipelines are retrieved in reverse along the pipeline placement trench. During the retrieval process, the pipelines are checked for wear and damage. Damaged pipelines are repaired or replaced to complete the entire TBM tunnel construction process.

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