Open TBM construction method in soft rock environment with high ground stress and large deformation
By assessing the geological environment and implementing support measures under high ground stress, the problem of initial support failure caused by soft rock deformation was solved, thus achieving stable tunneling of open-face TBMs and improving construction safety.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA RAILWAY TUNNEL GROUP CO LTD
- Filing Date
- 2023-08-09
- Publication Date
- 2026-06-30
AI Technical Summary
Under high ground stress, soft rock is prone to deformation, leading to the failure of initial support, which affects the normal tunneling of open-face TBMs, and also poses safety hazards and low construction efficiency.
By measuring ground stress and surrounding rock deformation rate, the geological environment is assessed. Advanced pilot holes are used to explore the geological conditions. Excavation cutters and fiberglass anchors are installed, polyurethane chemical grout is injected, pipe roofs and small guide pipes are installed, concrete of different materials is backfilled, steel bars and constant group anchor cables are laid, shotcrete is used for sealing, and stress relief holes are set up to achieve stable support for the surrounding rock.
Effective control of surrounding rock deformation, improvement of support strength and stability, ensuring smooth TBM tunneling, reducing the risk of cavity expansion, and improving construction safety and efficiency.
Smart Images
Figure CN117307185B_ABST
Abstract
Description
Technical Field
[0001] This invention application relates to the field of open-type TBM construction technology, specifically to an open-type TBM construction method for soft rock with large deformation under high ground stress. Background Technology
[0002] Open-face TBM, short for full-face rock tunnel boring machine, is a large-scale tunneling equipment that integrates multiple functions such as tunneling, muck removal, guidance, support, ventilation and dust control, with rock strata as the target of tunneling. It can simultaneously carry out construction processes such as tunneling, support and muck removal and operate continuously. It has the advantages of fast tunneling speed, environmental protection and high comprehensive benefits. It can realize the rapid construction of long tunnels in complex geographical terrain that is difficult to achieve with traditional drill and blast methods.
[0003] Under high ground stress, the softer rock in fractured zones makes the matrix (clay minerals) within the rock skeleton highly susceptible to slippage and expansion. This is followed by expansion and slippage plastic deformation of defects or cracks, leading to soft rock deformation. However, under high ground stress, the initial support structure within the tunnel struggles to effectively control the large deformation of soft rock caused by high stress, resulting in severe end-face convergence. This, in turn, causes the tunnel arches to twist and deform. The twisting deformation of the steel arches can potentially cause the open-type TBM's travel track to overturn, the rear trailer to shift, or even the open-type TBM's travel wheels to derail, restricting space and damaging facilities in relevant areas of the open-type TBM. Repeated disassembly and replacement of deformed arches has resulted in low construction efficiency, significant delays in the project schedule, and prominent safety hazards, including a substantial risk of collapse.
[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 an open-type TBM construction method in a soft rock environment with large deformation under high ground stress, aiming to solve the technical problem that the easy deformation of soft rock under high ground stress leads to the failure of initial support, thereby affecting the normal tunneling of open-type TBMs.
[0006] According to one aspect of this disclosure, an open-type TBM construction method is provided for soft rock with large deformation under high ground stress, comprising the following steps:
[0007] (1) Determine the hardness of the surrounding rock based on the tunneling parameters of the open-face TBM and the shield pressure; measure the ground stress and classify the measured ground stress data according to the principle that the greater the ground stress, the higher the grade; and analyze the deformation rate of the surrounding rock based on the monitoring data; and then determine the geological environment of the open-face TBM.
[0008] (2) Conduct advance drilling through the advance guide hole reserved at the open TBM cutterhead to explore the geological conditions in front of the tunnel.
[0009] (3) Install an enlarged cutter at the cutterhead of the open-type TBM and enlarge it by 10-15cm in the direction of the cutterhead radius;
[0010] (4) Several glass fiber anchors are installed in the cutter head towards the working face, and polyurethane chemical grout is injected into each of the glass fiber anchors;
[0011] (5) Several pipe roofs are constructed through guide holes with an outward inclination angle of 5° to 10° within a 120° range at the top of the shield, and several small guide pipes with an outward inclination angle of 40° to 50° are constructed within a 120° range at a position 2m to 2.5m behind the tail of the shield, and polyurethane chemical grout is injected into each pipe roof and small guide pipe respectively.
[0012] (6) If a cavity collapses at the support shoe location and the cavity collapses less than 3m, polypropylene coarse fiber concrete is poured into the cavity for backfilling; if the cavity collapses more than 3m, cast-in-place concrete is used for backfilling; loose material within the support shoe area is consolidated by small guide pipes and double grout injection.
[0013] (7) If a cavity collapses at the arch location and the cavity collapses less than 3m, steel pipes and polypropylene coarse fiber concrete shall be used for backfilling, and drainage pipes shall be pre-embedded; if the cavity collapses more than 3m, steel pipes and polypropylene coarse fiber concrete shall be used for backfilling, followed by M30 mortar layer backfilling, and drainage pipes shall be pre-embedded.
[0014] (8) Lay steel bars within a 120° range of the top arch and install constant anchor cables within a 270° range of the side top arch. At certain intervals, lay square steel arch frames with concrete poured into the internal cavity. A number of steel sections in a circular array are longitudinally connected between the square steel arch frames.
[0015] (9) The entire circle is sealed with shotcrete;
[0016] (10) Several stress relief holes are drilled within a 270° range of the top arch.
[0017] In some embodiments of this disclosure, in step (1), when the ground stress is 5 to 10 MPa, the ground stress is determined to be Level I; when the ground stress is 10 to 15 MPa, the ground stress is determined to be Level II; and when the ground stress is greater than 15 MPa, the ground stress is determined to be Level III.
[0018] In some embodiments of this disclosure, in step (1), the surrounding rock is determined to be slightly deformed when the deformation rate is ≤10mm / d; slightly deformed when the deformation rate is 10-30mm / d; moderately deformed when the deformation rate is 30-50mm / d; and severely deformed when the deformation rate is ≥50mm / d.
[0019] In some embodiments of this disclosure, in step (2), the advance drilling is performed in cycles of 20m with an overlap of 5m, and the geological conditions in front of the tunnel are obtained by combining the induced polarization method and the three-dimensional seismic wave method.
[0020] In some embodiments of this disclosure, in step (4), the glass fiber anchor bolt includes a plurality of extended glass fiber anchor bolts horizontally arranged along the tunnel axis, and a plurality of ordinary glass fiber anchor bolts horizontally arranged at the corresponding position of the cutter head center or at the corresponding position of the cutter head edge at a certain angle to the cutter head. The arrangement density of the ordinary glass fiber anchor bolts at the top position of the cutter head is greater than the arrangement density at the bottom position of the cutter head.
[0021] In some embodiments of this disclosure, in step (4) and / or step (5), the polyurethane chemical grout is prepared in equal volume ratios of component A and component B; and a circulating grouting process is adopted when injecting the polyurethane chemical grout, with the grouting pressure controlled in the range of 0.1 to 0.3 MPa, until the injection rate is ≤0.2 L / min, and then the grouting continues for at least 15 minutes before ending the grouting.
[0022] In some embodiments of this disclosure, in step (5), plum blossom-shaped holes are respectively opened along each cross section within a certain length of the front end of the pipe shed, and there is a certain included angle between the plum blossom-shaped holes at adjacent cross sections.
[0023] In some embodiments of this disclosure, in step (8), the constant group anchor cable is anchored with resin anchoring agent, the anchoring length is not less than 2m, the exposed length after anchoring is 250mm to 350mm, and the anchoring force is not less than 300KN.
[0024] One or more technical solutions provided in the embodiments of this application have at least one of the following technical effects or advantages:
[0025] 1. Concrete is poured into the square steel arch frame to achieve external constraint and improve the bearing capacity of the concrete. Furthermore, through the structural characteristics of the square steel, the combined effect of these two methods can greatly enhance the support strength of the square steel arch frame, increase the upper limit of the stress, ensure the stability and reliability of the support when soft rock deforms under high ground stress, and avoid deformation under stress that would restrict the TBM tunneling.
[0026] 2. In adverse geological conditions, the use of constant-group anchor cables for stabilization has a high success rate and can effectively and promptly converge the stress-controlled sections of the surrounding rock.
[0027] 3. By using advanced pilot holes and tunneling data, it is possible to predict the surrounding geological environment, which can improve the accuracy and reliability of geological prediction.
[0028] 4. Using concrete mortar with different material ratios to backfill cavities of different locations and sizes can achieve full filling of the cavities, stabilize the rock mass inside the cavities, prevent further collapse, and the corresponding drainage pipes can release water in the rock strata in a timely manner to avoid instability of the surrounding rock caused by water pressure.
[0029] 5. Several stress relief holes drilled within a 270° range of the top arch can effectively disperse the high ground stress in the surrounding rock, thereby helping to improve the stability of the support and ensuring the smooth tunneling of the TBM. Attached Figure Description
[0030] Figure 1 This is a front view schematic diagram of a glass fiber anchor bolt applied at the cutter head in one embodiment of this application.
[0031] Figure 2 This is a side view of a glass fiber anchor bolt installed at the cutter head in one embodiment of this application.
[0032] Figure 3 This is a schematic diagram of grouting within the collapsed cavity in one embodiment of this application.
[0033] Figure 4 This is a schematic diagram of the backfilling of the collapsed cavity in an embodiment of this application.
[0034] In the above figures, 1 is the cutterhead, 2 is the fiberglass anchor, 21 is the extended fiberglass anchor, 22 is the ordinary fiberglass anchor, 3 is the open TBM, 4 is the small conduit, 5 is the cement-water glass double-liquid grout, 6 is the polypropylene coarse fiber concrete, 7 is the mortar layer, and 8 is the drainage pipe. Detailed Implementation
[0035] 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.
[0036] This example discloses an open-type TBM construction method for soft rock with large deformation under high ground stress, which specifically includes the following steps:
[0037] (1) Determine the hardness of the surrounding rock based on the tunneling parameters of the open-face TBM and the shield pressure; measure the ground stress and classify the measured ground stress data according to the principle that the greater the ground stress, the higher the grade; and analyze the deformation rate of the surrounding rock based on the monitoring data; and then determine the geological environment of the open-face TBM.
[0038] Due to the complex underground environment, the excavation of open-face TBMs faces significant uncertainties. To accurately grasp the geological conditions ahead of the open-face TBM and avoid problems such as surrounding rock collapse that could trap the TBM or cause initial support deformation that hinders normal excavation, this embodiment collects and analyzes geological environment information around the TBM from multiple perspectives. This allows for accurate identification of unstable geological factors and timely implementation of effective and targeted solutions to ensure smooth TBM excavation. Specifically, in this example, the hardness of the surrounding rock is determined based on excavation parameters such as the open-face TBM's excavation speed, cutterhead rotation speed, cutterhead torque, and cutterhead propulsion force, as well as the shield pressure value. Ground stress is also measured and classified according to the measurement data. Specifically, in this example, ground stress of 5–10 MPa is classified as Level I (mild); ground stress of 10–15 MPa is classified as Level II (moderate); and ground stress greater than 15 MPa is classified as Level III (severe). Furthermore, after preliminary analysis and assessment of the hardness of the surrounding rock and classification of the surrounding environmental stress level, the deformation rate of the surrounding rock was measured and analyzed. In this case, a deformation rate ≤10mm / d was considered relatively minor deformation; a deformation rate of 10–30mm / d was considered minor deformation; a deformation rate of 30–50mm / d was considered moderate deformation; and a deformation rate ≥50mm / d was considered severe deformation. Therefore, the safety of the TBM tunneling environment was determined based on the hardness of the surrounding rock, the stress level, and the deformation rate.
[0039] (2) Conduct advance drilling through the advance guide hole reserved at the open TBM cutterhead to explore the geological conditions in front of the tunnel.
[0040] To investigate the geological conditions ahead of the open-face TBM and pre-treat weak surrounding rock or cavities, in this embodiment, advance exploratory boreholes are drilled towards the tunnel face through advance guide holes at the TBM cutterhead. This allows for the determination of the geological structure ahead of the tunnel face based on the borehole samples. In this example, each advance drilling cycle is 20m with a 5m overlap. Due to the limitations of geological exploration using advance guide holes, this example also incorporates induced polarization (IP) method to further and more accurately grasp the geological information ahead. This method explores geological problems by analyzing the differences in rock conductivity and IPV characteristics, and uses three-dimensional seismic wave analysis to reflect the geological morphology, thereby obtaining the geological conditions ahead of the tunnel.
[0041] Based on the assessment of the geological conditions, corresponding measures need to be taken. This case involves a section of the Dianzhong Water Diversion Project. According to geological exploration, the environment around the open TBM is affected by high ground stress and is located in a fracture zone with soft rock. The risk of collapse and breakage is relatively high. Therefore, subsequent support measures are taken to reinforce and stabilize the surrounding soft geological environment.
[0042] (3) Install a widening cutter at the cutterhead of the open-type TBM and widen it by 10-15cm in the direction of the cutterhead radius.
[0043] First, the excavation operation is carried out using the excavation cutter installed on the TBM cutterhead. Due to the instability of the rock mass, in order to prevent partial collapse caused by large-scale excavation, the excavation distance is set to 15cm in this case, so as to provide subsequent support space and play a stabilizing role for the surrounding rock.
[0044] (4) Install several glass fiber anchors in the cutter head towards the working face, and inject polyurethane chemical grout into each glass fiber anchor.
[0045] Surveying revealed that the geological environment in front of the tunnel face was relatively unstable. To prevent the TBM from being affected by unstable geological conditions and high ground stress during tunneling, which could lead to collapse in front of the cutterhead, several fiberglass anchor bolts were installed from inside the cutterhead towards the tunnel face in this case. See details below. Figures 1-2 In this example, the fiberglass anchor bolts include several extended fiberglass anchor bolts 21 horizontally arranged along the tunnel axis, and several ordinary fiberglass anchor bolts 22 horizontally arranged at the corresponding position of the cutterhead center or at the corresponding position of the cutterhead edge at a certain angle to the cutterhead. Thus, the extended fiberglass anchor bolts 21 provide initial stabilization and reinforcement of the rock mass at the center of the tunnel to be excavated along the tunnel axis, and the remaining ordinary fiberglass anchor bolts 22 further stabilize the rock mass and working face near the cutterhead. In addition, in this embodiment, considering that the top rock mass is more prone to collapse, the density of ordinary fiberglass anchor bolts at the top of the cutterhead is greater than the density at the bottom of the cutterhead, thereby reducing the risk of collapse before support.
[0046] In addition, after each fiberglass anchor is drilled, grouting is required inside the anchor to enhance its strength and anchoring effect. In this case, considering the special geological environment of weak surrounding rock and high ground stress, polyurethane chemical grout is injected into the fiberglass anchor. The polyurethane chemical grout is prepared according to the equal volume ratio of component A and component B to achieve the best performance and ensure the stability of the surrounding rock in front of the cutterhead and the tunnel face during the excavation process. To ensure the grouting is dense, a circulating grouting process is adopted when injecting polyurethane chemical grout. Every 4m is used for advance reinforcement, and the grouting pressure is controlled within the range of 0.1 to 0.3MPa. When the injection rate is ≤0.2L / min, grouting is continued for at least 15 minutes before the grouting is stopped to ensure the anchoring effect.
[0047] (5) Several pipe roofs are constructed through guide holes with an outward inclination angle of 5° to 10° within a 120° range at the top of the shield, and several small guide pipes with an outward inclination angle of 40° to 50° are constructed within a 120° range at a position 2m to 2.5m behind the tail of the shield. Polyurethane chemical grout is injected into each pipe roof and small guide pipe respectively.
[0048] Considering the support effect of the shield's curvature and the influence of gravity on the loose rock mass, in this example, nine Φ76mm pipe roofs, each 20m long and with an overlap of 10mm, were alternately installed within a 120° range at the top of the shield through nine guide holes with an outward inclination angle of 5°. These pipe roofs were constructed using seamless steel pipes with a wall thickness of 6mm. To ensure effective grouting, staggered openings were made along the cross-sections of each pipe within a 15.5m range at the front end of the pipes. Furthermore, to ensure even and sufficient grout overflow, a certain angle was maintained between the staggered openings at adjacent cross-sections, thus guaranteeing the support effect of the pipe roofs. In addition, considering that the tail of the shield gradually becomes exposed as the TBM advances, several small guide pipes with an outward inclination angle of 45° were installed within a 120° range at a position 2m behind the shield tail to ensure stability in this area, thereby achieving better support. Similarly, according to the grouting steps described in step (4), polyurethane chemical grout is injected into the pipe roof and small pipes to achieve the required strength.
[0049] (6) If a cavity collapses at the support shoe location, and the cavity is less than 3m, polypropylene coarse fiber reinforced concrete should be poured into the cavity for backfilling; if the cavity collapses more than 3m, cast-in-place concrete should be used for backfilling; loose material within the support shoe area should be consolidated using small guide pipes and double-slurry grouting; for details, please refer to Figure 4 .
[0050] Due to unstable geological structures, tunneling disturbances can easily lead to cavities around the TBM. When cavities appear, they must be sealed promptly to prevent further expansion and serious adverse consequences. In this example, if a cavity appears at the support shoe location and is less than 3m, an emergency sprayed concrete system will be used to backfill it with C25 polypropylene coarse fiber reinforced concrete; if the cavity is greater than 3m, C20 cast-in-place concrete will be used for backfilling. Additionally, see [link to relevant documentation]. Figure 3 Within the support shoe area, several small guide pipes with a length of 3.0m and a diameter of 42mm are installed and cement-water glass double liquid grout is injected to consolidate the loose body. The small guide pipes are arranged in an array with a spacing of 1m between each other and between rows. The grouting pressure is 0.1MPa to 0.5MPa.
[0051] (7) If a cavity collapses at the arch location and the cavity collapses less than 3m, steel pipes and polypropylene coarse fiber concrete shall be used for backfilling, and drainage pipes shall be pre-embedded; if the cavity collapses more than 3m, steel pipes and polypropylene coarse fiber concrete shall be used for backfilling, followed by M30 mortar layer backfilling, and drainage pipes shall be pre-embedded.
[0052] When a cavity collapses in the arch and is less than 3m in length, Φ76mm steel pipes of matching length to the cavity size are used, spaced 3.0m apart in both the ring and longitudinal directions. C25 polypropylene fiber reinforced concrete is then sprayed into the cavity for backfilling. Furthermore, due to the arch's special location, to prevent stress caused by groundwater pressure, 3m long, Φ42mm drainage pipes are pre-embedded during cavity sealing, spaced 3.0m apart in both the ring and longitudinal directions, to facilitate timely drainage of groundwater and release pressure on the weak surrounding rock. When the arch cavity collapses beyond 3m, Φ76mm steel pipes of matching length to the cavity size are used, spaced 3.0m apart in both the ring and longitudinal directions. After partial backfilling with C25 polypropylene fiber reinforced concrete, M30 mortar is used for layered backfilling, with the mortar backfill height not exceeding 3.0m. Additionally, several 6m long, Φ42mm drainage pipes are pre-embedded at the same 3m ring and longitudinal spacing.
[0053] (8) Lay steel bars within a 120° range of the top arch and install constant anchor cables within a 270° range of the side top arch. At certain intervals, lay square steel arch frames with concrete poured into the internal cavity. A number of steel sections in a circular array are longitudinally connected between the square steel arch frames.
[0054] Furthermore, to achieve reliable support for weak surrounding rock and avoid difficulties in support replacement and impact on TBM excavation due to initial support failure under high ground stress, a square steel-concrete arch frame is installed in the widened section in this example. This arch frame is supported by high-strength square steel and filled with core concrete. This utilizes external constraints to improve the load-bearing capacity of the internal concrete, while minimizing the risk of local instability of the external constraint material. Both methods fully leverage their respective advantages, achieving high-strength and high-rigidity support requirements with relatively low support costs. In this embodiment, the filling concrete inside the pipe is micro-expansion C40 fine aggregate concrete; in other embodiments, micro-expansion M40 cement mortar is used. In this example, the square steel-concrete arch frames are spaced 0.5m apart, and I20b semi-sectioned steel sections are arranged circumferentially with a longitudinal spacing of 0.5m between adjacent arch frames to achieve longitudinal connection between the arch frames and improve their load-bearing strength.
[0055] In this example, to improve the support strength, constant-group anchor cables are installed within a 270° range of the top arch. These anchor cables have a high success rate and can promptly converge the stress control section of the surrounding rock. Specifically, 10m long, Φ21.8mm constant-group anchor cables are used, with a circumferential and longitudinal spacing of 1m, arranged in a staggered pattern, and anchored with resin anchoring agent. The anchoring length is not less than 2m, and the exposed length after anchoring is 250mm to 350mm, with an anchoring force of not less than 300KN. In addition, Φ12mm steel bars are laid within a 120° range of the top arch, and the steel bars are fixed to the constant-group anchor cables to improve the overall stress strength and ensure the support effect. In other embodiments, eight tapered anchor bolts are installed at each arch frame, and W-shaped steel strips are added circumferentially to improve the stress strength. Additionally, 6m long, Φ38mm self-drilling anchor bolts are installed within a 90° range of the tunnel floor, with a spacing of 1m between rows.
[0056] In addition, in this embodiment, each square steel concrete arch frame includes several ring segments, and each ring segment is provided with a flange node at the end, thereby forming the tunnel cross-sectional outline. Furthermore, the arch frame is provided with four Φ30 vent holes at equal intervals, one of which is located at the highest point of the arch frame, and the other vent holes are provided with Φ70 grouting holes on the side. Thus, the grout overflow status of the highest vent hole can be used to determine whether the square steel arch frame is grouted tightly.
[0057] (9) The entire circle is sealed with shotcrete.
[0058] After the anchor cables, steel bars, and square steel concrete arch frame are completed, the completed parts are sealed with full-circle shotcrete. In this example, polypropylene coarse fiber C25 concrete with a shotcrete thickness of 25cm is used to place the square steel concrete arch frame and other structures inside the concrete as a supporting structure to avoid collapse and breakage caused by high ground stress.
[0059] (10) Several stress relief holes are drilled within a 270° range of the top arch.
[0060] In this embodiment, considering that the open TBM is in a high ground stress environment, several stress relief holes with a depth of 6m and a diameter of 50mm are drilled within the 270° range of the side arch that is prone to collapse due to stress. This allows some stress to be released into the holes, alleviating the squeezing effect of the rock mass and reducing the adverse effects of ground stress on the tunnel.
[0061] Although some preferred embodiments of this application 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 this invention.
[0062] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of the invention. Therefore, if such modifications and variations to this application fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.
Claims
1. An open-type TBM construction method for soft rock with large deformation under high ground stress, characterized in that, Includes the following steps: (1) Determine the hardness of the surrounding rock based on the tunneling parameters of the open-face TBM and the shield pressure; measure the ground stress and classify the measured ground stress data according to the principle that the greater the ground stress, the higher the grade; and analyze the deformation rate of the surrounding rock based on the monitoring data; and then determine the geological environment of the open-face TBM. (2) Conduct advance drilling through the advance guide hole reserved at the open TBM cutterhead to explore the geological conditions in front of the tunnel. (3) Install an enlarged cutter at the cutterhead of the open-type TBM and enlarge it by 10-15cm in the direction of the cutterhead radius; (4) Several glass fiber anchors are installed in the cutter head towards the working face, and polyurethane chemical grout is injected into each of the glass fiber anchors; (5) Several pipe roofs are constructed through guide holes with an outward inclination angle of 5° to 10° within a 120° range at the top of the shield, and several small guide pipes with an outward inclination angle of 40° to 50° are constructed within a 120° range at a position 2m to 2.5m behind the tail of the shield, and polyurethane chemical grout is injected into each pipe roof and small guide pipe respectively. (6) If a cavity collapses at the support shoe location and the cavity collapses less than 3m, polypropylene coarse fiber concrete is poured into the cavity for backfilling; if the cavity collapses more than 3m, cast-in-place concrete is used for backfilling; loose material within the support shoe area is consolidated by small guide pipes and double grout injection. (7) If a cavity collapses at the arch location and the cavity collapses less than 3m, steel pipes and polypropylene coarse fiber concrete shall be used for backfilling and drainage pipes shall be pre-embedded; if the cavity collapses more than 3m, steel pipes and polypropylene coarse fiber concrete shall be used for backfilling and then M30 mortar shall be used for layered backfilling and drainage pipes shall be pre-embedded. (8) Lay steel bars within a 120° range of the top arch and install constant anchor cables within a 270° range of the side top arch. At certain intervals, lay square steel arch frames with concrete poured into the internal cavity. A number of steel sections in a circular array are longitudinally connected between the square steel arch frames. (9) The entire circle is sealed with shotcrete; (10) Several stress relief holes are drilled within a 270° range of the top arch.
2. The open-type TBM construction method for soft rock with large deformation under high ground stress according to claim 1, characterized in that, In step (2), the advance drilling is carried out in cycles of 20m with an overlap of 5m, and the geological conditions in front of the tunnel are obtained by combining the induced polarization method and the three-dimensional seismic wave method.
3. The open-type TBM construction method for soft rock with large deformation under high ground stress according to claim 1, characterized in that, In step (4), the glass fiber anchor includes several extended glass fiber anchors horizontally arranged along the tunnel axis, and several ordinary glass fiber anchors horizontally arranged at the corresponding position of the cutter head center or at the corresponding position of the cutter head edge at a certain angle to the cutter head. The arrangement density of the ordinary glass fiber anchors at the top position of the cutter head is greater than the arrangement density at the bottom position of the cutter head.
4. The open-type TBM construction method for soft rock with large deformation under high ground stress according to claim 1, characterized in that, In step (4) or step (5), the polyurethane chemical grout is prepared according to the ratio of equal volume of component A and component B; and when injecting the polyurethane chemical grout, a circulating grouting process is adopted, and the grouting pressure is controlled within the range of 0.1 to 0.3 MPa until the injection rate is ≤0.2 L / min, and then the grouting continues for at least 15 minutes before the grouting ends.
5. The open-type TBM construction method for soft rock with large deformation under high ground stress according to claim 1, characterized in that, In step (5), plum blossom-shaped holes are opened along each cross section within a certain length of the front end of the pipe shed, and there is a certain angle between the plum blossom-shaped holes at adjacent cross sections.
6. The open-type TBM construction method for soft rock with large deformation under high ground stress according to claim 1, characterized in that, In step (8), the constant group anchor cable is anchored with resin anchoring agent, the anchoring length is not less than 2m, the exposed length after anchoring is 250mm to 350mm, and the anchoring force is not less than 300KN.