Construction method of lateral ear hole of TBM tunnel under complex geological environment

Abstract

This invention discloses a method for constructing lateral side openings in TBM tunnels under complex geological conditions, aiming to solve the technical problems of poor safety and low efficiency in traditional construction methods under complex geological conditions. Before constructing the side opening, a three-dimensional geological model is built and a warning threshold is set. When the detected data exceeds the warning threshold, an alarm is triggered and construction parameters are adjusted. A folding sliding track equipped with excavation equipment is deployed near the TBM equipment on the side of the side opening to be excavated. Small guide pipe holes and anchor bolt holes are drilled along the outer side of the excavation outline at the designed opening location of the side opening. After installing a double-section H175 steel arch frame optimized by finite element topology, shotcrete is used to seal and form a locking structure. Once the locking structure reaches the design strength, the side opening is excavated from the inside of the locking structure using a partitioned-step coupled excavation algorithm, and unbonded anchor cables are installed at the edge arch of the excavated side opening area. This method makes the excavation of side openings in complex geological environments extremely safe and efficient.

Description

Technical Field

[0001] This invention relates to the field of TBM construction technology, specifically to a method for constructing lateral side openings in TBM tunnels under complex geological conditions. Background Technology

[0002] Full-face tunnel boring machines (TBMs) are the mainstream equipment in modern tunnel construction, with advantages such as fast excavation speed, good tunnel quality, and minimal disturbance to the surrounding rock. However, during TBM construction, it is often necessary to excavate side chambers (such as refuge chambers, equipment storage chambers, turning chambers, etc.) to facilitate equipment maintenance, personnel refuge, or tunnel turning.

[0003] When tunnels traverse complex geological areas such as active fault zones (e.g., areas with high ground stress, large deformation of soft rock, fault fracture zones, and water-rich strata), the extremely poor geological conditions, including fractured surrounding rock, developed groundwater, and high ground stress, lead to significant problems with large deformation of soft rock. Traditional geological prediction methods, relying on single sensors or manual interpretation, struggle to accurately predict adverse geological formations such as faults, fracture zones, and water-rich areas ahead of the tunnel face, resulting in high construction risks. Furthermore, the TBM (Tunnel Boring Machine) occupies a large portion of the tunnel space, making the construction space for lateral tunnels extremely limited, hindering the application of conventional equipment and methods, thus increasing the difficulty and risk of lateral tunnel construction and reducing excavation efficiency. Additionally, during lateral tunnel construction, the complex geological conditions make it difficult for traditional excavation methods to effectively control the deformation of the surrounding rock within the tunnel area, failing to meet the excavation and support requirements under complex geological conditions. Traditional support structures are prone to deformation and failure, potentially leading to collapses.

[0004] The information disclosed in this background section is intended only to enhance the understanding of the background technology of this disclosure and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0005] In view of at least one of the above technical problems, this disclosure provides a method for constructing lateral abutments in TBM tunnels under complex geological conditions, aiming to solve the technical problems of poor construction safety and low efficiency of traditional construction methods under complex geological conditions.

[0006] According to one aspect of this disclosure, a method for constructing lateral side openings in TBM tunnels under complex geological conditions is provided, comprising the following steps: (1) Before the ear hole is constructed, geological exploration is carried out in the ear hole area by using ground-penetrating radar, sonic detector and advanced directional drilling core sampling on the side of the TBM equipment. The collected geological data are calibrated, filtered and fused in sequence to construct a three-dimensional geological model. Warning thresholds including surrounding rock strain energy density and water inflow are set. When the detection data reaches or exceeds the warning threshold, an alarm is triggered and the construction parameters are adjusted accordingly. (2) At the corresponding position of the TBM equipment near the side of the ear hole to be excavated, a folding sliding track with excavation equipment is arranged in the direction of TBM tunneling. The excavation equipment includes a sliding platform for moving along the folding sliding track, a folding arm fixed at the sliding platform, and an operating end corresponding to the end of the folding arm, including a bucket and a drilling machine. When the ear hole is excavated, the working position of the excavation equipment is adjusted according to the designed position of the ear hole and the TBM tunneling speed. (3) Drill small guide pipe holes and anchor bolt holes at the opening location of the ear hole along the outer side of the excavation outline, and insert self-sealing grouting small guide pipes and stretchable anchor bolts for grouting and anchoring; then install the double H175 steel arch frame optimized by finite element topology and weld it to the small guide pipes and anchor bolts, and then spray concrete to seal and form the lock structure. (4) After the lock structure reaches the design strength, the ear hole is excavated from the inside of the lock. During the excavation of the ear hole, the partition-step coupling excavation algorithm is used to dynamically adjust the excavation parameters, including the vertical step height and the axial segment length. After each certain excavation advance, initial support is immediately carried out and unbonded anchor cables are applied to the side arch of the excavated ear hole range.

[0007] In some embodiments of this disclosure, in step (1), the adjustment of construction parameters includes the adjustment of ear hole excavation parameters and TBM tunneling parameters, and when the surrounding rock strain energy density and water inflow index exceed the set threshold, the TBM thrust is correspondingly reduced by 10-20. % Reduce the speed by 5-10. rpm Simultaneously increase the grouting pressure by 0.5–1 MPa.

[0008] In some embodiments of this disclosure, the construction of the three-dimensional geological model in step (1) includes the following steps: (11) Obtain the layered structure and discontinuity information of the strata based on the electromagnetic wave reflection signal of the ground radar; determine the elastic parameters and structural characteristics of the strata based on the propagation speed and reflection signal of the acoustic detector in the strata; and obtain the lithology, structure and water content information of the strata based on advanced directional drilling core sampling. (12) The collected raw geological data are calibrated and filtered to remove noise and interference signals, and the geological data from each region are fused to form a comprehensive geological dataset; (13) Based on the distribution and complexity of the geological data, the exploration area is divided into several grid units that represent specific geological bodies. In each grid unit, a geometric model of the corresponding geological body, including stratum thickness, dip angle, and strike parameters, is constructed according to the geological data. Each geological body is assigned corresponding physical and mechanical properties, including lithology, density, elastic modulus, and compressive strength. (14) The three-dimensional geological model is dynamically adjusted based on the geological deformation, stress and water pressure parameters obtained in real time by the sensor network deployed in the construction area, and the geometric shape and attribute parameters of the corresponding geological body are updated.

[0009] In some embodiments of this disclosure, in step (2), the folding sliding track includes a main support that is hinged to the TBM auxiliary equipment, a hydraulic cylinder that is fixed to the main support perpendicular to the hinge axis of the main support and has a tapered pin fixed to its movable end, and a pin hole seat that is fixed to the TBM auxiliary equipment along the axial direction of the hydraulic cylinder; the side and top of the pin hole seat near the ear hole are respectively provided with pin holes that match the taper of the tapered pin and have a certain depth.

[0010] In some embodiments of this disclosure, in step (3), the self-sealing grouting conduit includes a tapered portion with an expanded diameter structure and a plurality of sealing rings fixed at the middle position of the self-sealing grouting conduit; the sealing rings are made of a water-swellable material.

[0011] In some embodiments of this disclosure, in step (3), the two H-beams in the double H175 steel arch frame optimized by finite element topology have flanges of unequal thickness, and the flange thickness near the TBM side is greater than the flange thickness on the opposite side; the web of the double H175 steel arch frame is provided with a weight reduction hole, and the long axis of the weight reduction hole is set along the direction of the principal stress trace.

[0012] In some embodiments of this disclosure, step (4) of the partition-level coupled excavation algorithm specifically includes the following steps: (41) Monitor the surrounding rock strain in real time based on the strain sensor network deployed within the ear hole construction area, and calculate the surrounding rock strain energy density U in real time; (42) Set the threshold value of the surrounding rock strain energy density according to the geological conditions and construction requirements; (43) Calculate the step height and corresponding step segment length dynamically based on the real-time surrounding rock strain energy density, and adjust the ear hole excavation parameters accordingly when the surrounding rock strain energy density exceeds the set threshold.

[0013] In some embodiments of this disclosure, in step (4), the unbonded anchor cable includes an unbonded anchor cable body, a corrugated sleeve sleeved outside the unbonded anchor cable body, and a retarding resin layer for filling the space between the corrugated sleeve and the anchor cable hole wall and between the corrugated sleeve and the unbonded anchor cable body.

[0014] One or more technical solutions provided in the embodiments of this application have at least one of the following technical effects or advantages: 1. By integrating geological data obtained from ground-penetrating radar, sonic detection, and advanced directional drilling before and after excavation, a high-precision and highly reliable three-dimensional geological model is constructed. By setting early warning thresholds, when indicators such as the surrounding rock strain energy density and water inflow exceed the set thresholds, the construction parameters can be adjusted accordingly to achieve closed-loop feedback, which can effectively reduce the probability of geological disasters and ensure the safety of construction.

[0015] 2. The foldable sliding track enables rapid release and recovery of the TBM's lateral space, avoiding obstruction of the TBM's normal personnel and material passages during non-excavation periods. Furthermore, by using excavation equipment operating on the foldable sliding track, the excavation equipment's operation is matched with the TBM's tunneling speed, ensuring the relative stability of the tunneling equipment's position and enabling ear-hole excavation without stopping the TBM. At the same time, hydraulic pins ensure the stability of the equipment under vibration environments.

[0016] 3. Based on the surrounding rock strain energy density, the partition-decomposition coupled excavation dynamically partitions the excavation range. The partition height and segment length can be adjusted in real time according to the surrounding rock strain energy density, thereby achieving effective control of the deformation of the surrounding rock in complex geological environments.

[0017] 4. The ear piercing lock structure adopts a topology-optimized double H175 steel arch frame, which reduces the weight of the arch frame while improving the bending stiffness. The other high-strength tensile anchor rods and self-sealing grouting small pipes are welded together to bear the stress, which can significantly improve the stability of the ear piercing opening area.

[0018] 5. The unbonded anchor cable adopts a dual anchoring mechanism with the combined action of corrugated sleeve and retarding resin. The micro-protrusions on the surface of the corrugated sleeve increase the interlocking between the sleeve and the borehole wall, and the retarding resin forms a chemical bond, which significantly improves the anchoring force of the anchor cable and solves the problem of traditional anchor cables being prone to failure in complex geological environments. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the layout of excavation equipment at the TBM auxiliary equipment location in a tunnel according to one embodiment of this application.

[0020] Figure 2 This is a schematic diagram of the layout of unbonded anchor cables in one embodiment of this application.

[0021] In the above figures, 11 is the tunnel, 12 is the side hole, 13 is the TBM auxiliary equipment, 2 is the sliding track, 3 is the sliding platform, 4 is the folding arm, 5 is the actuating end, 6 is the surrounding rock of the side hole, 7 is the unbonded anchor cable, 71 is the corrugated sleeve, 72 is the unbonded anchor cable body, and 73 is the anchor cable hole. Detailed Implementation

[0022] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inner", "outer", "vertical", "horizontal", "clockwise", "counterclockwise", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0023] The programs involved or relied upon in the following embodiments are all conventional or simple programs in this technical field. Those skilled in the art can make conventional choices or adaptive adjustments according to specific application scenarios.

[0024] To better understand the technical solution of this application, the above technical solution will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] In complex geological environments such as fractured surrounding rock, well-developed groundwater, and high ground stress, the traditional method of constructing lateral tunnels presents challenges, including difficulties in advance detection, poor support effects, limited construction space, and low construction efficiency. These issues severely impact the safety and schedule of lateral tunnel excavation. Therefore, this example, using a tunnel traversing a complex geological area of ​​an active fault zone, discloses a method for constructing a lateral tunnel in a TBM tunnel under complex geological conditions. In this case, at a certain mileage of the tunnel, a permanent equipment storage chamber (tunnel) is designed to be excavated laterally to the TBM. The chamber is 5.5m wide, 6.5m high, and 12m deep. The geological conditions in this section are extremely complex, as revealed by preliminary geological exploration, exhibiting adverse geological characteristics such as large deformation of soft rock and softening upon contact with water. Specifically, the method for constructing a lateral tunnel in this complex geological environment includes the following steps: (1) Before the ear hole is constructed, geological exploration is carried out in the ear hole area by using ground radar, sonic detector and advanced directional drilling core sampling on the side of the TBM equipment. The collected geological data are calibrated, filtered and fused in sequence to construct a three-dimensional geological model. Warning thresholds including surrounding rock strain energy density and water inflow are set. When the detection data reaches or exceeds the warning threshold, an alarm is triggered and the construction parameters are adjusted accordingly.

[0026] Considering that traditional advanced detection methods are difficult to accurately obtain geological information in complex geological environments, thus failing to provide a reliable basis for tunnel excavation, and frequently encountering sudden geological situations during construction, such as sudden water inrush and surrounding rock collapse, seriously affecting construction safety and progress, this embodiment first conducts geological exploration before the ear hole construction. In this example, ground-penetrating radar, sonic detectors, and advanced directional drilling core sampling are used to conduct geological exploration in the ear hole area. Then, based on the geological exploration data, a corresponding three-dimensional geological model is established, and the accurate three-dimensional geological model guides the subsequent ear hole excavation.

[0027] Specifically, in this embodiment, the establishment of the three-dimensional geological model includes the following sub-steps: (11) Obtain information on the layered structure and discontinuities of the strata based on the electromagnetic wave reflection signal of the ground radar; determine the elastic parameters and structural characteristics of the strata based on the propagation speed and reflection signal of the sonic detector in the strata; and obtain information on the lithology, structure and water content of the strata based on advanced directional drilling core sampling.

[0028] Specifically, in this example, the ground-penetrating radar (GPR) system used is the ProEx model manufactured by MALA GmbH of Sweden, equipped with both 100MHz and 250MHz shielded antennas. In this case, three longitudinal survey lines and five transverse survey lines were arranged on the face and sidewalls of the tunnel, with a line spacing of 0.5m and a point spacing of 0.1m. The longitudinal survey lines were placed at the center line of the face, 1.5m to the left, and 1.5m to the right, covering the entire height of the face. The transverse survey lines were placed at the bottom, 1.5m, 3.0m, 4.5m, and top of the face, covering the entire width of the face. For the data acquisition parameters of this GPR system, the time window was set to 200ns, the number of sampling points to 512, the number of superpositions to 16, and the scan rate to 64 scans / second. A point-based measurement method was used, triggering a data acquisition every 0.1m of movement. During on-site data acquisition, it was ensured that the antenna was in close contact with the rock surface, and a coupling agent was applied to reduce air coupling interference. Therefore, by analyzing the electromagnetic wave reflection signals from the strata, information on the strata's layered structure and discontinuities can be obtained.

[0029] In this example, the acoustic wave detector used is the RS-ST01D intelligent acoustic wave detector manufactured by Wuhan Yanhai Company, equipped with a dual-hole, single-transmitter, dual-receiver probe. In this embodiment, a total of six acoustic wave detection holes were arranged around the ear hole, with a depth of 12m and a diameter of 75mm. Two holes were arranged at the arch, tilted upwards at a 5° angle, spaced 1.5m apart; two holes were arranged horizontally on each of the two side walls, spaced 1.5m apart; and two holes were arranged at the bottom plate, tilted downwards at a 5° angle, spaced 1.5m apart. The test employed a cross-hole method, with a single transmitter and dual receiver, a transmission voltage of 500V, a sampling interval of 0.5μs, a sampling length of 2048 points, and the probe was raised every 0.2m to perform the full-section test. The dynamic elastic modulus and dynamic Poisson's ratio of the surrounding rock were calculated based on the longitudinal and transverse wave velocities measured on-site.

[0030] During the advanced directional drilling coring, a C6 multi-functional drilling rig was used, equipped with a dual-tube single-action coring process. A total of three advance exploratory boreholes (holes 1, 2, and 3) were arranged in a triangular pattern at the tunnel face, with a depth of 30m and a diameter of 91mm. Specifically, borehole 1 was located 1.0m to the left of the center of the tunnel face, with a horizontal angle of 0° and an azimuth aligned with the tunnel axis; borehole 2 was located 1.0m to the right of the center of the tunnel face, with a horizontal angle of 5° upward and an azimuth of 3° to the right; and borehole 3 was located 1.0m below the center of the tunnel face, with a horizontal angle of 3° downward and an azimuth of 3° to the left. During drilling, drilling speed, torque, and propulsion pressure were recorded every 1m of drilling. Double-layer core tubes were used for coring, with a core diameter of 63mm. Each drilling pass was 2.5m, and the average core recovery rate was 92%. The extracted rock cores were cataloged on-site, including lithological description, RQD index calculation, joint and fracture statistics, and water content observation.

[0031] (12) The collected raw geological data are calibrated and filtered to remove noise and interference signals, and the geological data from each region are fused to form a comprehensive geological dataset.

[0032] After acquiring the relevant geological data, the ground-penetrating radar data underwent background removal, gain adjustment, and bandpass filtering; the acoustic data underwent first arrival picking, wave velocity calculation, and spectrum analysis; and the core data underwent lithological description, RQD index calculation, and water content testing. These processes effectively remove noise and interference signals, improving the accuracy and reliability of the data. These data processing methods are standard practices in the field and will not be elaborated further in this example.

[0033] After calibration and filtering, to improve the accuracy and completeness of subsequent model building, this example fuses data acquired through different detection methods to form a comprehensive geological dataset. Specifically, this example uses the Kalman filter algorithm to perform spatiotemporal registration and feature-level fusion of ground-penetrating radar, acoustic detection, and core data to form a comprehensive geological dataset. The fused data achieves a spatial resolution of 0.5m and includes attributes such as P-wave velocity, S-wave velocity, density, elastic modulus, Poisson's ratio, compressive strength, and RQD.

[0034] (13) Based on the distribution and complexity of geological data, the exploration area is divided into several grid units that represent specific geological bodies. In each grid unit, a geometric model of the corresponding geological body, including the thickness, dip angle, and strike parameters of the strata, is constructed according to the geological data. Each geological body is given corresponding physical and mechanical properties, including lithology, density, elastic modulus, and compressive strength.

[0035] Specifically, in this example, a tetrahedral grid was used to divide the exploration area into 50cm×50cm×50cm grid cells. Then, the Kriging interpolation algorithm was used to construct a geometric model of the geological body within each grid cell, including parameters such as stratum thickness, dip angle, and strike. Three-dimensional visualization software was used to display the spatial distribution of fault fracture zones and the range of water-rich areas. Furthermore, based on laboratory tests and empirical formulas, corresponding physical and mechanical properties were assigned to each geological body. In this embodiment, the lithology is classified into grades III, IV, and V, with densities of 2.65 g / cm³. 3 2.45 g / cm 3 2.20g / cm 3 The elastic moduli are 20 GPa, 8 GPa, and 2 GPa, respectively, and the compressive strengths are 80 MPa, 30 MPa, and 5 MPa, respectively.

[0036] (14) The three-dimensional geological model is dynamically adjusted based on the deformation, stress and water pressure parameters of the geological body obtained in real time by the sensor network deployed in the construction area, and the geometric shape and attribute parameters of the corresponding geological body are updated.

[0037] In this embodiment, a total of 20 multi-point displacement gauges, 15 pressure cells, and 10 piezometers were deployed in the construction area to monitor the deformation, stress, and water pressure parameters of the geological body in real time. Each sensor had a sampling frequency of 100Hz and measurement accuracies of 0.1mm (displacement), 0.01MPa (pressure), and 0.001MPa (water pressure), respectively. Data from each sensor was transmitted to the data acquisition unit via a CAN bus and then transmitted in real time to the data processing center via a fiber optic network. To enable dynamic adjustment of the 3D model based on the real-time sensor data and accurately reflect actual geological changes during construction, a sequential Gaussian simulation algorithm was used in this example. The 3D geological model was dynamically adjusted every 10 minutes based on real-time monitoring data, updating the geometric shape and attribute parameters of the geological body. This dynamic model update resulted in clearer boundaries of fault fracture zones and more accurate water pressure distribution in water-rich areas.

[0038] Therefore, by establishing a three-dimensional geological model, potential geological hazards such as faults, fracture zones, and water-rich areas within the construction area can be effectively predicted. This allows for the early development of corresponding construction plans and countermeasures, improving construction efficiency and safety. Furthermore, real-time monitoring of geological deformation during construction not only enables the timely detection of potential geological hazards but also allows for dynamic updates to the geological model based on real-time monitoring data. This allows for dynamic adjustment of construction parameters, ensuring the safety and stability of the construction process.

[0039] Furthermore, the inventors discovered in practice that although the TBM main unit and the tunnel are located in different spatial positions, they belong to the same geomechanical system. Therefore, when the TBM tunnels through complex geological sections, the tunneling loads (thrust, torque, vibration) generated by it will propagate through the rock mass to the surrounding areas, directly affecting the stress field in the tunnel area. Conversely, the redistribution of surrounding rock stress caused by tunnel excavation may also have a reaction effect on the TBM tunneling area. To further improve construction safety, an early warning threshold is set in this embodiment. When the detected data reaches or exceeds the early warning threshold, an alarm is triggered and the tunnel excavation parameters are adjusted accordingly (including dynamically adjusting the step height, segment length, and support strength based on the surrounding rock strain energy density), and the TBM construction parameters are adjusted simultaneously.

[0040] Specifically, in this example, the threshold value for the surrounding rock strain energy density is set to 0.5 KJ / m³. 3 The inflow threshold is 50m³. 3 / h, when abnormal geological conditions in the tunnel affect the safety of the TBM main unit, and when the surrounding rock strain energy density and water inflow exceed the set threshold, the system will adjust the TBM tunneling parameters accordingly: reducing the TBM thrust by 10-20. % Reduce the speed by 5-10. rpmSimultaneously, the grouting pressure was increased by 0.5–1 MPa. This, combined with threshold alarm-linked adjustments to construction parameters, ensured that TBM tunneling parameters were automatically adjusted according to pre-defined rules once monitoring data reached the warning threshold. This reduced the disturbance of the tunneling area by the TBM and prepared construction parameters for the risky sections the TBM was about to enter. Using this method, three fault fracture zones and two water inrush events were successfully warned during construction, reducing the probability of sudden geological disasters by 31%.

[0041] (2) At the corresponding position of the TBM equipment near the side of the ear hole to be excavated, a folding sliding track equipped with the excavation equipment is set up along the TBM excavation direction.

[0042] TBM equipment occupies a significant amount of space within the tunnel, resulting in extremely limited working space when performing tasks such as excavating side tunnels. In this case, there was a mere 1.2m of narrow working space on each side of the TBM. Traditionally, when constructing side tunnels with the TBM, the machine is shut down, and its auxiliary equipment is removed to make room for the tunnel construction. However, the dismantling and transportation of these auxiliary equipment is difficult and time-consuming, and the complete cessation of TBM excavation during tunnel construction severely impacts the construction schedule.

[0043] Therefore, in this embodiment, see Figure 1 A sliding rail 2 is fixedly installed at the TBM auxiliary equipment 13, and the sliding rail 2 is laid parallel to the TBM's tunneling direction. The excavation equipment sliding along the sliding rail moves in the opposite direction to the TBM's tunneling direction. While the TBM continues to tunnel, the position of the excavation equipment in the absolute spatial coordinate system remains constant, thereby realizing continuous construction of the ear hole without stopping the TBM.

[0044] One issue is that fixing the sliding rail near the tunnel excavation side in the TBM rear support area would inevitably block the pedestrian passage between the TBM rear support area and the tunnel, affecting personnel passage and material transportation. Furthermore, tunnel excavation is not entirely straight; it often includes curved sections with turning radii of several hundred degrees. The sliding rail fixed to the TBM rear support area would interfere with the TBM's turns and could not adapt to the tunnel's curvature. Additionally, the inventors discovered in practice that the TBM generates strong vibrations during excavation, and the fixed rail, subjected to long-term vibration, would suffer fatigue damage, reducing its service life. Therefore, in this embodiment, a foldable sliding rail 2 is specifically adopted. Specifically, this sliding rail includes a main support structure using a truss structure. The main support specifically includes longitudinal beams, transverse beams, and diagonal braces that are connected to each other. This truss structure reduces the weight of the main support while maintaining the structural strength of the frame. In addition, the main support has a hinge point on the longitudinal beam near the TBM side. It is hinged to the beam of the TBM auxiliary equipment through the hinge seat. The hinge axis of each hinge part is parallel to the axis of the TBM auxiliary equipment. In this example, the rotation angle of each hinge part is 90°. As a result, the main support can be flipped down (unfolded) or flipped up (folded) around each hinge axis.

[0045] However, the TBM generates vibrations during excavation, which can cause the main support to vibrate, affecting the accuracy and reliability of the ear hole excavation process. Therefore, in this embodiment, several hydraulic pins are used to lock the main support. Specifically, each hydraulic pin includes a hydraulic cylinder fixed to the main support perpendicular to its hinge axis. The actuating end of the hydraulic cylinder faces the TBM auxiliary equipment side, and a tapered pin is fixed at the actuating end. Correspondingly, a pin hole seat is fixed to the TBM auxiliary equipment along the axis of the hydraulic cylinder. The pin hole seat has pin holes on its side near the ear hole and on its adjacent top surface. The taper of the pin holes matches the taper of the tapered pin and has a certain depth. Therefore, when the main support is unfolded, the actuating end of the driving hydraulic cylinder extends, and the tapered pin of the actuating end precisely engages with the pin hole on the side of the pin seat; and when the main support is flipped upwards and folded, the actuating end of the driving hydraulic cylinder extends again, and the tapered pin of the actuating end precisely engages with the pin hole at the top of the pin seat, thereby achieving a limiting function and ensuring the stability of the main support in both unfolded and folded states. In some other embodiments, the hydraulic cylinder is also equipped with a self-locking structure as in the prior art to ensure the stable and reliable operation of the cylinder. Testing showed that in this example, under a 20Hz vibration condition, the displacement of the hydraulic pin was less than 0.2mm, fully meeting the stability requirements.

[0046] Furthermore, the sliding track 2 is fixed to the main support, and the sliding track can be deployed as needed by folding and unfolding the main support, avoiding obstruction of personnel and material passage during normal tunneling. In this embodiment, during the excavation of the ear hole, a sliding platform 3 is slidably installed at the sliding track 2. This sliding platform is equipped with a servo motor drive, enabling precise speed control. Additionally, a folding arm 4 is fixedly installed on the top surface of the sliding platform 3, and an actuating end 5 is fixedly installed at the end of the folding arm 4. In this example, the actuating end includes a bucket and a drilling machine. Thus, the working position of the excavation equipment can be moved as needed via the sliding platform 3, matching its speed with the TBM's tunneling speed, enabling fixed-position excavation operations. Furthermore, the folding arm 4 effectively expands the range of motion of the actuating end and can be folded and stored during normal TBM tunneling, reducing space occupation. To achieve dynamic balance between the movement of the sliding platform and the tunneling of the TBM, thus ensuring the relative stability of the excavation equipment without stopping the TBM, this example also includes a TBM speed sensor installed at the TBM's propulsion cylinder to measure the TBM's tunneling speed. Laser sensors are also installed at both ends of the sliding track to measure the absolute position of the excavation equipment on the track. In other embodiments, an accelerometer is also installed at the folding arm 4 for vibration monitoring and compensation.

[0047] (3) Drill small guide pipe holes and anchor bolt holes at the opening location of the ear hole along the outer side of the excavation outline, and insert self-sealing grouting small guide pipes and stretchable anchor bolts for grouting and anchoring; then install the double H175 steel arch frame optimized by finite element topology and weld it to the small guide pipes and anchor bolts, and then spray concrete to seal and form the lock structure.

[0048] Through long-term practice and research, the inventors discovered that the opening of the ear hole is a stress concentration zone. Excavation disturbance will immediately trigger a redistribution of stress in the surrounding rock, causing damage to the surrounding rock at the opening in the early stages of ear hole excavation. Therefore, to ensure the construction safety of the TBM's lateral ear hole, this example constructs a complete combined interlocking structure at the designed opening location of the ear hole before formal excavation. The main excavation of the ear hole is only carried out after the interlocking structure reaches its design strength.

[0049] Specifically, small guide pipes and anchor bolts are first installed at the designed opening locations of the ear-shaped opening for advance support. In this embodiment, 80cm outward from the ear-shaped opening excavation outline, a 5m long, 42mm Φ, and 3.5mm thick small guide pipe is drilled using a drilling machine; and 30cm outward from the arch excavation outline at the opening, a locking anchor bolt is installed. During the drilling of the small guide pipe holes, the outward insertion angle is set to 5°–10° to ensure the small guide pipe can penetrate deep into the surrounding rock; during the drilling of the anchor bolt holes, the upward inclination angle is set to 15°±2° to allow the anchor bolt to extend into the stable rock layer above the arch.

[0050] In practice, the inventors discovered that traditional small-diameter guide pipe installation involves drilling a hole slightly larger than the guide pipe's diameter. After the guide pipe enters the hole, the opening is sealed with quick-setting cement or an anchoring agent to prevent grout leakage. However, this sealing material is prone to shrinkage and cracking, leading to grout leakage and making it difficult to increase the grouting pressure. Therefore, based on traditional methods, this embodiment employs a self-sealing small-diameter guide pipe. Specifically, the self-sealing guide pipe includes a tapered section with an expanded diameter at the front end. During insertion, the tapered section compresses and expands loose rock debris within the hole, ensuring smooth insertion of the guide pipe. Furthermore, two sealing rings are fixed to the outside of the guide pipe. To prevent the sealing rings from being scratched during insertion, water-swellable rubber is used, which has a small initial volume but expands upon contact with water after insertion. After grouting begins (pressure 1-2 MPa), the grout enters the gap between the guide pipe and the borehole wall. The sealing ring expands upon contact with water, increasing its outer diameter and allowing it to contact the borehole wall for sealing. As the grouting pressure gradually increases (pressure 3-5 MPa), the high-pressure grout compresses the sealing ring, causing further deformation and a tighter fit against the borehole wall. In this example, at a grouting pressure of 5 MPa, the expansion coefficient of the sealing ring is not less than 300%, resulting in a complete seal. Therefore, by placing a sealing ring in the middle of the guide pipe, the grout channel is significantly blocked, reducing leakage from the traditional 12% to 0.5%.

[0051] After grouting and anchoring the self-sealing grouting conduit and the stretchable anchor bolts, the steel arch frame is installed. However, through long-term practice and research, the inventors have found that traditional steel arch frames can only use standard steel sections in design and use. To improve stiffness, the cross-section must be increased, resulting in a significant increase in the weight of the steel arch frame. In addition, the stress on different parts of the steel arch frame cross-section is uneven, and the material utilization rate is low. Therefore, in this embodiment, a double-section H175 steel arch frame optimized by finite element topology is used. The traditional standard H175 steel section is uniform, with a flange thickness of 11mm and a web thickness of 7mm, and is consistent along its entire length. In this example, the double-section H175 steel section, after topology optimization, achieves a variable cross-section. Considering that the arch crown region mainly bears compression and bending, the flange thickness is increased to 14mm and the web thickness is reduced to 6mm. Considering that the arch foot region bears compression, bending, and shear, the flange thickness is increased to 12mm and the web thickness to 9mm. Furthermore, the connection area between the arch crown and arch foot is locally reinforced, increasing the flange thickness in this area to 16mm. In addition, while traditional H-beams have equal flange thickness at the same cross-section location, the flanges in this example are designed with unequal thickness based on the asymmetry of the stress on the opening (stronger constraint and greater rock pressure on the side closer to the TBM, and weaker constraint and relatively less stress on the other side). Specifically, the flange thickness (higher compressive stress) on the side closer to the TBM is greater than the flange thickness (relatively lower tensile stress) on the other side. In this embodiment, weight-reducing holes are also provided in areas of lower stress in the steel web. In this example, the weight-reducing holes are specifically elliptical, with their major axis aligned along the stress trajectory. This reduces the weight of the steel section while avoiding any impact on its stiffness. Furthermore, traditional double-section structures require separate welded connecting plates, whereas in this example, the connecting plate between the steel sections is integrally rolled or welded to the steel sections, forming a continuous corrugated connecting plate. This makes the connecting plate and the steel section a unified design, serving both a connecting function and bearing loads. Simultaneously, it optimizes the dynamic loads caused by TBM vibration, using the dynamic loads as topology optimization constraints. Field practice in this example shows that the double-section H175 steel arch frame, optimized using finite element topology, achieves a 15% weight reduction and a significant increase in stiffness, while simultaneously increasing the moment of inertia by 200%. This means its bending stiffness is three times that of the traditional design.

[0052] After the double-section H175 steel arch frame is in place, it is welded and fixed to the small guide pipe and anchor rod to ensure overall stress. Then, shotcrete is sprayed to seal the rock surface in time to prevent weathering and form a bond with the surrounding rock. In this example, the initial shotcrete thickness is 5cm. After the initial shotcrete has set, a second shotcrete is sprayed with a designed thickness of 17.5cm to ensure the integrity and stability of the support structure.

[0053] (4) After the lock structure reaches the design strength, the ear hole is excavated from the inside of the lock. During the excavation of the ear hole, the partition-step coupling excavation algorithm is used to dynamically adjust the excavation parameters, and initial support is carried out immediately after each certain excavation depth.

[0054] When constructing lateral tunnels using a TBM under extremely complex geological conditions, traditional excavation methods employ fixed step heights and segment lengths, which are unsuitable for sudden geological changes such as fault fracture zones and large deformations in soft rock, often leading to excessive deformation of the surrounding rock or even collapse accidents. Furthermore, full-face excavation requires extensive support work, resulting in low construction efficiency. In addition, traditional methods rely heavily on manual experience for decision-making, leading to delayed response and high construction risks. Therefore, in this embodiment, a partitioned-step coupled excavation algorithm is used to dynamically adjust excavation parameters, including vertical step height and axial segment length, during tunnel excavation. This algorithm uses the surrounding rock strain energy density as a real-time control index, achieving precise control of surrounding rock deformation through dynamic adjustment of excavation parameters.

[0055] Specifically, high-precision strain sensors and pressure cells are first deployed in the construction area to build a real-time monitoring network. Stress and strain data of the surrounding rock are continuously collected, serving as the data foundation for the zoned-stage coupled excavation algorithm. In this example, the surrounding rock strain energy density U is calculated in real time using edge computing nodes. The calculation of the surrounding rock strain energy density is a standard procedure in this field and will not be elaborated upon here. Three warning thresholds are set according to the type of surrounding rock. For example, in this embodiment, for Class IV surrounding rock (soft rock), the three warning thresholds are set as U1 = 0.2 KJ / m³. 3 U2 = 0.4 KJ / m 3 U3 = 0.4 kJ / m 3 That is, when the surrounding rock strain energy density U of soft rock is less than 0.2 kJ / m 3 When the surrounding rock strain energy density U of soft rock is within the normal range of 0.2–0.4 KJ / m, it is considered within the normal range. 3 The area is designated as a warning zone when the surrounding rock strain energy density U of the soft rock is greater than 0.4 KJ / m³. 3 The area was determined to be within a dangerous zone. Furthermore, a dynamic relationship was established between the step height H and the surrounding rock strain energy density U: H = H0 × f (U), where H0 is the reference step height (4.85 m in this example). f (U) represents the segmentation adjustment coefficient; specifically, in this embodiment, when U exceeds the first-level threshold, the step height decreases linearly, and when U exceeds the second-level threshold, it decreases further, down to a minimum of 0.2 times the baseline value (i.e., the soft rock area can be reduced to 2 m). Simultaneously, the segment length L is dynamically adjusted based on the step height and the exposure time of the working face. Specifically, in this example, the segment length L = L0 × g(H, t), where L0 is the base segment length (5.5 m in this example). g (H, t) = min(1, (H / H0) × (t0 / t)), where t is the actual exposure time and t0 is the baseline exposure time (24 h in this example). Furthermore, in this example, the algorithm executes automatically every 10 minutes, dynamically updating excavation parameters including the excavation step height H and step segment length L, thus forming a closed-loop control system of monitoring, calculation, adjustment, and execution.

[0056] In practical engineering applications, during the construction of the lateral tunnel using a TBM in this example, the excavation work was carried out using excavation equipment operating on a folding sliding track. When excavation reached the fault fracture zone, the surrounding rock strain energy density U increased from 0.18 KJ / m³. 3 It surged to 0.42 KJ / m 3 This triggered a level-two early warning, leading to adjustments in the step height from 4.85 m to 2.4 m and the segment length from 5.5 m to 4.0 m, effectively curbing the continued rise of the U-value. Throughout the construction process, the maximum deformation of the surrounding rock was controlled at 85 mm, a 53% reduction compared to traditional methods (average 180 mm). Simultaneously, dynamic adjustments avoided rework and reinforcement due to excessive deformation, improving construction efficiency by 43.8% and reducing cycle time from 8 hours to 4.5 hours. By dynamically adjusting excavation parameters based on real-time geological conditions, surrounding rock deformation can be effectively controlled, construction efficiency improved, construction risks reduced, and safety and stability ensured during construction.

[0057] After the ear hole is excavated, initial support is carried out in a timely manner. In this embodiment, shotcrete is immediately sprayed to seal the surrounding rock after the ear hole is excavated, and the thickness of the initial shotcrete is 5cm. Then, steel mesh is laid and steel arch frame is installed to ensure stable support. At the same time, anchor bolts are also installed in this example to ensure a tight fit between the arch frame and the surrounding rock. Finally, shotcrete is sprayed to the designed thickness of 17.5cm to ensure the integrity and stability of the support structure.

[0058] In the construction of lateral ear holes in TBMs, anchor cables are typically required. However, the inventors have found in practice that existing unbonded anchor cables usually consist of steel strands, anti-corrosion lubricant, a PE sheath, and ordinary grout (usually cement mortar). The anchoring section only comes into direct contact with the grout after the PE pipe is removed. In soft rock formations with large deformation, traditional unbonded anchor cables are prone to slippage failure at the interface with the surrounding rock, resulting in a sharp decrease in the anchoring force. In water-rich formations, the grout of traditional unbonded anchor cables is easily diluted or washed away by groundwater, forming grouting voids and weakening the anchoring effect. Therefore, in this embodiment, an unbonded anchor cable with double anchoring by a corrugated sleeve and retarding resin is used. The unbonded anchor cable is installed immediately after the excavation cycle of the side arch of the ear hole is completed.

[0059] Specifically, after completing the excavation of a segment of the ear hole, the exposed surrounding rock 6 of the side arch is immediately sealed with a 5cm thick layer of initial shotcrete. Then, anchor cable holes are drilled on the initial shotcrete surface at the designed intervals. In this embodiment, the diameter of the anchor cable holes is 75mm, the hole depth is 10m, and the downward inclination angle is set to 10°. See [link to documentation]. Figure 2 After drilling the anchor hole 73, the unbonded anchor cable 7 is installed. First, a corrugated sleeve 71 with a wall thickness of 2mm and micro-protrusions on its surface is inserted into the hole. In this example, the corrugated sleeve 71 is made of high-strength plastic or composite material to provide good corrosion resistance and mechanical strength. In this embodiment, the unbonded anchor cable body consists of steel strands, a grease layer coated on the surface of the steel strands, and a PE sleeve covering the grease layer. Then, the unbonded anchor cable body 72, after the PE sleeve has been removed and cleaned, is inserted into the center of the corrugated sleeve. The centering of the unbonded anchor cable body can be ensured by a centering bracket. Subsequently, a high-pressure grouting pump is used to inject retarded resin grout into the corrugated sleeve. In this example, the retarded resin is specifically polyurethane-modified epoxy resin with a gel time of 30 minutes. In addition, the grouting pressure of the retarded resin in this example is 1.0 MPa to ensure that the grout can fill the gap between the sleeve and the hole wall. After the retarding resin has cured for 24 hours, the anchor cable is tensioned in stages to the design locking load of 250kN. Finally, sprayed concrete is applied to a design thickness of 17.5cm to completely encapsulate the anchor and the pad. This creates a mechanical interlocking and limiting effect between the corrugated sleeve surface protrusions and the surrounding rock, while the retarding resin forms a chemical bond with the anchor cable and the surrounding rock. This dual anchoring significantly improves the anchoring force of the unbonded anchor cable in this example. Field pull-out tests showed that the peak load of the unbonded anchor cable in this example reached 450kN, an increase of approximately 36.4% compared to the peak load of approximately 330kN for traditional anchor cables. Furthermore, the corrugated sleeve also plays a role in pressure maintenance and guidance during grouting. Combined with the water-resistant dilution properties of the retarding resin, the unbonded anchor cable in this example can achieve 100% grout saturation even in water-rich strata, reducing the grout leakage rate from the traditional 12% to 0.5%. In practical use, when the surrounding rock displacement reaches 200mm, the unbonded anchor cable in this example can still maintain 85% of the anchoring force without brittle fracture or slippage, effectively solving the problem of anchor cable failure in soft rock strata with large deformation.

[0060] Although some preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0061] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this application and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for constructing lateral side openings in TBM tunnels under complex geological conditions, characterized in that, Includes the following steps: (1) Before the ear hole is constructed, geological exploration is carried out in the ear hole area by using ground-penetrating radar, sonic detector and advanced directional drilling core sampling on the side of the TBM equipment. The collected geological data are calibrated, filtered and fused in sequence to construct a three-dimensional geological model. Warning thresholds including surrounding rock strain energy density and water inflow are set. When the detection data reaches or exceeds the warning threshold, an alarm is triggered and the construction parameters are adjusted accordingly. (2) At the corresponding position of the TBM equipment near the side of the ear hole to be excavated, a folding sliding track with excavation equipment is arranged in the direction of TBM tunneling. The excavation equipment includes a sliding platform for moving along the folding sliding track, a folding arm fixed at the sliding platform, and an operating end corresponding to the end of the folding arm, including a bucket and a drilling machine. When the ear hole is excavated, the working position of the excavation equipment is adjusted according to the designed position of the ear hole and the TBM tunneling speed. (3) Drill small guide pipe holes and anchor bolt holes at the opening location of the ear hole along the outer side of the excavation outline, and insert self-sealing grouting small guide pipes and stretchable anchor bolts for grouting and anchoring; then install the double H175 steel arch frame optimized by finite element topology and weld it to the small guide pipes and anchor bolts, and then spray concrete to seal and form the lock structure. (4) After the lock structure reaches the design strength, the ear hole is excavated from the inside of the lock. During the excavation of the ear hole, the partition-step coupling excavation algorithm is used to dynamically adjust the excavation parameters, including the vertical step height and the axial segment length. After each certain excavation advance, initial support is immediately carried out and unbonded anchor cables are applied to the side arch of the excavated ear hole range.

2. The application method according to claim 1, characterized in that, In step (1), the construction parameter adjustment includes the adjustment of the ear hole excavation parameters and the TBM tunneling parameters. When the surrounding rock strain energy density and water inflow index exceed the set threshold, the TBM thrust is correspondingly reduced by 10-20. % Reduce the speed by 5-10. rpm Simultaneously increase the grouting pressure by 0.5–1 MPa.

3. The application method according to claim 1, characterized in that, In step (1), the construction of the three-dimensional geological model includes the following steps: (11) Obtain the layered structure and discontinuity information of the strata based on the electromagnetic wave reflection signal of the ground radar; determine the elastic parameters and structural characteristics of the strata based on the propagation speed and reflection signal of the acoustic detector in the strata; and obtain the lithology, structure and water content information of the strata based on advanced directional drilling core sampling. (12) The collected raw geological data are calibrated and filtered to remove noise and interference signals, and the geological data from each region are fused to form a comprehensive geological dataset; (13) Based on the distribution and complexity of the geological data, the exploration area is divided into several grid units that represent specific geological bodies. In each grid unit, a geometric model of the corresponding geological body, including stratum thickness, dip angle, and strike parameters, is constructed according to the geological data. Each geological body is assigned corresponding physical and mechanical properties, including lithology, density, elastic modulus, and compressive strength. (14) The three-dimensional geological model is dynamically adjusted based on the geological deformation, stress and water pressure parameters obtained in real time by the sensor network deployed in the construction area, and the geometric shape and attribute parameters of the corresponding geological body are updated.

4. The application method according to claim 1, characterized in that, In step (2), the folding sliding track includes a main support that is hinged to the TBM auxiliary equipment, a hydraulic cylinder that is fixed to the main support perpendicular to the hinge axis of the main support and has a tapered pin fixed to its movable end, and a pin hole seat that is fixed to the TBM auxiliary equipment along the axial direction of the hydraulic cylinder; the side and top of the pin hole seat near the ear hole are respectively provided with pin holes that match the taper of the tapered pin and have a certain depth.

5. The application method according to claim 1, characterized in that, In step (3), the self-sealing grouting conduit includes a tapered part with an expanded diameter structure and several sealing rings fixed at the middle position of the self-sealing grouting conduit; the sealing rings are made of a water-swellable material.

6. The application method according to claim 1, characterized in that, In step (3), the two H-beams in the double H175 steel arch frame optimized by finite element topology have flanges of unequal thickness, and the flange thickness near the TBM side is greater than the flange thickness on the opposite side; the web of the double H175 steel arch frame is provided with weight reduction holes, and the long axis of the weight reduction holes is set along the direction of the principal stress trace.

7. The application method according to claim 1, characterized in that, In step (4), the partition-level coupled excavation algorithm specifically includes the following steps: (41) Monitor the surrounding rock strain in real time based on the strain sensor network deployed within the ear hole construction area, and calculate the surrounding rock strain energy density U in real time; (42) Set the threshold value of the surrounding rock strain energy density according to the geological conditions and construction requirements; (43) Calculate the step height and corresponding step segment length dynamically based on the real-time surrounding rock strain energy density, and adjust the ear hole excavation parameters accordingly when the surrounding rock strain energy density exceeds the set threshold.

8. The application method according to claim 1, characterized in that, In step (4), the unbonded anchor cable includes an unbonded anchor cable body, a corrugated sleeve sleeved on the unbonded anchor cable body, and a retarding resin layer for filling the space between the corrugated sleeve and the anchor cable hole wall and between the corrugated sleeve and the unbonded anchor cable body.

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