A method for excavating and constructing large-section tunnels in complex geological conditions
By adopting the methods of sectional excavation and enhancing the bearing capacity of the arch foot in large-section tunnels with complex geology, the problems of surrounding rock instability and lining cracks were solved, thereby improving the safety and stability of tunnel construction.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- GUONENG ECONOMIC & TECH RES INST CO LTD
- Filing Date
- 2026-01-22
- Publication Date
- 2026-07-17
AI Technical Summary
In the construction of large-section tunnels under complex geological conditions, the problems of surrounding rock instability and lining cracks are serious, and the existing blasting excavation methods pose a threat to tunnel safety and project quality.
A zoned excavation method was adopted, with blasting excavation used in hard rock areas and mechanical excavation used in soft and loose rock areas. Vibration monitoring and parameter optimization were carried out during blasting. Combined with measures to enhance the bearing capacity of the arch foot, such as multi-stage segmented blasting and steel arch reinforcement, a three-dimensional support system was formed.
It effectively reduced the disturbance of the surrounding rock caused by blasting, improved the safety and stability of tunnel construction, reduced the generation of lining cracks, and improved construction efficiency and project quality.
Smart Images
Figure CN121556868B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of tunnel excavation technology, specifically to a method for excavating and constructing large-section tunnels in complex geological conditions. Background Technology
[0002] As highway construction continues to extend into mountainous areas, the number of tunnels with special and complex geological conditions is gradually increasing. During the construction of mountain tunnels, especially large-section highway tunnels in soft rock with poor engineering mechanical properties, there are characteristics of large deformation, fast deformation rate, and long deformation time. These characteristics can cause the deformation scale of the weak surrounding rock to exceed the conventional dimensions, leading to the dangers of surrounding rock instability and collapse, and lining cracking, which seriously affect the safety and quality of tunnel construction.
[0003] Chinese invention patent application number CN202010716875.7 discloses a blasting excavation method for a large-section granite tunnel in Class V surrounding rock. Although this method can excavate the tunnel, it still has obvious shortcomings: its excavation scheme is relatively complex and involves many procedures. Moreover, it only adopts the single excavation scheme of blasting excavation. Blasting excavation will inevitably cause serious dynamic disturbance damage to the soft large-section tunnel surrounding rock, thereby threatening the safety of the tunnel lining. Summary of the Invention
[0004] In view of this, the present invention provides a method for excavating and constructing large-section tunnels in complex geological conditions, which effectively curbs the instability of surrounding rock and the generation of lining cracks, and ensures the safety and quality of tunnel construction.
[0005] This invention provides a method for excavating and constructing large-section tunnels in complex geological conditions, comprising: S1. Dividing the tunnel face into at least one hard rock mass zone and at least one soft and loose rock mass zone according to the surrounding rock grade; setting a blasting vibration buffer zone at the end of the soft and loose rock mass zone near the hard rock mass zone; using blasting excavation for the hard rock mass zone and mechanical excavation for the soft and loose rock mass zone; when using blasting excavation for the hard rock mass zone, monitoring and analyzing the tunnel blasting vibration, optimizing the blasting parameters, and controlling the blasting vibration velocity within the allowable value of the blasting procedure; S2. Taking measures to enhance the bearing capacity of the arch foot of the excavated surrounding rock.
[0006] Beneficial effects: By adopting different excavation methods according to different rock mass materials, the disturbance to the surrounding rock is reduced, thereby effectively curbing the instability of the surrounding rock; by enhancing the bearing capacity of the arch foot area, the generation of lining cracks is effectively curbed.
[0007] In one optional implementation, the optimization of blasting parameters includes at least one of the following: multi-stage segmented blasting design, adjustment of explosive dosage, optimization of borehole distribution, and optimization of the number of boreholes; wherein, multi-stage segmented blasting design refers to dividing the hard rock mass area into multiple regions, and detonating the side away from the soft and loose rock mass area first, thereby forming free faces in sequence.
[0008] Beneficial effects: Effectively avoids the risk of damage to the surrounding rock caused by blasting vibration, ensuring the safety and stability of tunnel excavation and construction.
[0009] In one optional implementation, when designing a multi-stage segmented blasting operation, the hard rock mass area is divided into an upper bench, a middle bench, a lower bench, and an invert. These are excavated sequentially from top to bottom. During the excavation of the upper bench, primary support is constructed simultaneously. When the excavation reaches the boundary between the upper and middle benches and the primary support is simultaneously constructed to the same boundary, the arch foot area of the upper and middle benches is reinforced. After the primary support of the upper bench is completed, the middle bench is excavated, and primary support is constructed simultaneously. When the excavation reaches the boundary between the middle and lower benches and the primary support is simultaneously constructed to the same boundary, the arch foot area of the middle and lower benches is reinforced. After the primary support of the middle bench is completed, the lower bench is excavated, and primary support is constructed simultaneously. When the excavation reaches the invert and the primary support is simultaneously constructed to the invert, a steel arch frame for the invert is laid above the invert, and both ends of the steel arch frame are fixedly connected to the primary support. Simultaneously, the arch foot area of the invert is reinforced.
[0010] Beneficial effects: By reinforcing the arch foot area at different locations, the bearing capacity of the primary support is improved, thereby effectively curbing the generation of lining cracks.
[0011] In one alternative embodiment, the reinforcement of the arch foot area of the invert arch includes: a diagonal bracing steel frame, one end of which is connected to the invert arch steel arch frame on the invert arch, and the other end of which is connected to the primary support.
[0012] Beneficial effects: By increasing the diagonal bracing steel frame, the load in the arch foot area of the inverted arch is distributed, the stress-bearing area is increased, and the effect of expanding the arch foot is achieved.
[0013] In one optional implementation, the reinforcement method for the arch foot area of the upper and middle steps is as follows: the arch foot area of the upper and middle steps is partially expanded and excavated, and after the expansion and hazard removal, a steel arch frame is installed; after the steel arch frame is installed, steel pipes are installed by drilling holes perpendicular to the rock surface; after the steel pipes are installed, grout is injected into the inside of the steel pipes, and the steel pipes are welded to the steel arch frame.
[0014] Beneficial effects: The bearing capacity of the foundation in the arch foot area of the upper and middle steps was improved by partially expanding the excavation and installing steel arch frames; the bearing capacity of the primary support in the arch foot area of the upper and middle steps was improved by anchoring steel pipes into the rock mass and grouting reinforcement.
[0015] In one optional implementation, the reinforcement method for the arch foot area of the middle and lower steps is as follows: the arch foot area of the middle and lower steps is reinforced by partial excavation, and after the excavation is completed and the danger is removed, a steel arch frame is installed; after the steel arch frame is installed, steel pipes are installed by drilling holes perpendicular to the rock surface; after the steel pipes are installed, grout is injected into the inside of the steel pipes, and the steel pipes are welded to the steel arch frame.
[0016] Beneficial effects: The bearing capacity of the foundation in the arch foot area of the middle and lower steps was improved by partially expanding the excavation and installing steel arch frames; the bearing capacity of the primary support in the arch foot area of the middle and lower steps was improved by anchoring steel pipes into the rock mass and grouting reinforcement.
[0017] In one optional embodiment, the reinforcement of the arch foot area of the invert arch includes: drilling holes perpendicular to the downward direction of the invert arch and holes inclined to the downward direction of the invert arch at the ends of the invert arch steel arch frame; installing steel pipes in the holes; grouting inside the steel pipes after installation, and welding the steel pipes to the invert arch steel arch frame.
[0018] Beneficial effects: The addition of steel pipe anchoring effectively enhances the overall stability of the invert arch foot area and improves the cooperative stress-bearing performance of the invert arch and primary support.
[0019] In one alternative implementation, the reinforcing steel pipes in the arch foot area of the invert arch are reinforced by grouting with a two-component grout.
[0020] Beneficial effects: The dual-liquid grout solidifies rapidly, which can quickly seal the cracks in the rock mass, and play a role in quickly stopping water and reinforcing the surrounding rock.
[0021] In one alternative embodiment, the blasting vibration buffer zone is a plurality of energy release holes set at the interface between the weak and loose rock mass zone and the hard rock mass zone; and / or, the blasting vibration buffer zone is excavated mechanically.
[0022] Beneficial effects: The venting holes can unload some of the energy generated by the blasting, reduce the impact on the surrounding rock and provide convenience for mechanical demolition of the rock mass in the area.
[0023] In one optional implementation, the method further includes active reinforcement of the loosened surrounding rock; the active reinforcement method is as follows: based on the test results of the loosened surrounding rock zone, hollow grouting anchors are driven into the loosened surrounding rock, and grouting is performed on the hollow grouting anchors to reinforce the loosened surrounding rock.
[0024] Beneficial effects: By reinforcing the surrounding rock, the overall stability of the surrounding rock is improved, effectively preventing instability and collapse, and further ensuring the safety of tunnel construction. Attached Figure Description
[0025] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0026] Figure 1 This is a schematic diagram of a method for excavating and constructing a large-section tunnel in complex geological conditions, according to an embodiment of the present invention.
[0027] Figure 2 This is a schematic diagram of the tunnel excavation cross-section.
[0028] Explanation of reference numerals in the attached figures:
[0029] 1. Hard rock mass area; 2. Soft and loose rock mass area; 3. Energy release hole; 4. Upper bench; 5. Middle bench; 6. Lower bench; 7. Inverted arch; 8. Excavation boundary line of upper and middle benches; 9. Excavation boundary line of middle and lower benches; 10. Arch foot area of upper and middle benches; 11. Arch foot area of middle and lower benches; 12. Arch foot area of inverted arch. Detailed Implementation
[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0031] The following is combined Figures 1 to 2 The following describes embodiments of the present invention.
[0032] According to an embodiment of the present invention, a method for excavating and constructing a large-section tunnel in complex geological conditions is provided, comprising:
[0033] S1. A comprehensive geological survey of the tunnel excavation area was conducted, and the surrounding rock was classified into different grades based on its characteristics. According to the rock grade, the tunnel face was divided into at least one hard rock mass zone 1 and at least one soft and loose rock mass zone 2. A blasting vibration buffer zone was set up at the end of the soft and loose rock mass zone 2 near the hard rock mass zone 1. Multi-stage, segmented blasting excavation was used for the hard rock mass zone 1, while mechanical excavation was used as an auxiliary method for the soft and loose rock mass zone 2. This minimized the impact of the drill-and-blast method on the stability of large-section highway tunnels in soft rock, offering convenient operation and solving the problem of localized collapse and severe rockfall instability after excavation of large-section tunnels in complex geological conditions. The combined blasting and mechanical excavation reduced damage to the surrounding rock caused by over-excavation during blasting, while mechanical excavation allowed for more precise control of the excavation profile, reducing unnecessary over-excavation and under-excavation, and improving construction efficiency.
[0034] When using blasting excavation in the hard rock mass area 1, the tunnel blasting vibration was monitored and analyzed, and blasting parameters were optimized to control the blasting vibration velocity within the allowable values specified in the blasting regulations. Through intelligent monitoring and analysis of blasting data, various blasting design parameters were adjusted and optimized in a timely manner, effectively minimizing the impact of blasting vibration on the soft and loose rock mass area and ensuring that the disturbance to the surrounding rock caused by tunnel blasting excavation was minimized. By controlling the blasting vibration velocity within the allowable values specified in the blasting regulations, the damage caused by blasting vibration to the surrounding rock was further reduced, ensuring construction safety. By setting up a blasting vibration buffer zone, the energy generated by blasting could be effectively absorbed and dispersed, reducing the impact on the soft and loose rock mass area 2, thereby reducing the risk of surrounding rock instability.
[0035] S2. Measures to enhance the bearing capacity of the arch foot in the excavated surrounding rock. During tunnel excavation, the arch foot area is prone to deformation and failure due to insufficient bearing capacity. Enhancing the bearing capacity of the arch foot area can effectively improve the stability of the surrounding rock, thereby effectively curbing the generation of lining cracks.
[0036] More specifically, the methods for identifying the surrounding rock grade include geological description of the tunnel excavation face and identification of joint structure surfaces, thereby classifying the surrounding rock.
[0037] More specifically, a blasting vibration buffer zone of 1.5m-3m is reserved according to the geological conditions of the surrounding rock.
[0038] In one embodiment, blasting parameter optimization includes at least one of the following: multi-stage segmented blasting design, explosive dosage adjustment, borehole distribution optimization, and borehole number optimization. By optimizing the blasting parameters, the aim is to minimize damage to the installed lining during blasting excavation. Specifically, the multi-stage segmented blasting design involves dividing the hard rock mass zone 1 into multiple areas, with detonation starting from the side furthest from the soft, loose rock mass zone 2, sequentially forming free faces. These sequentially formed free faces guide the energy generated by the blast towards the free face direction, effectively reducing the impact of blasting vibrations on the soft, loose rock mass zone 2.
[0039] More specifically, when designing multi-stage segmented blasting, the hard rock mass area 1 is divided into upper bench 4, middle bench 5, lower bench 6 and invert arch 7; it is excavated in sequence from top to bottom; by carrying out segmented blasting excavation, the impact damage to the surrounding rock caused by blasting excavation is reduced.
[0040] While the upper step 4 is being excavated, the primary support is being constructed simultaneously. When the excavation reaches the upper middle step excavation boundary line 8 and the primary support is being constructed at the same time, the arch foot area 10 of the upper middle step is reinforced. This enhances the bearing capacity of this critical area and improves the stability of the primary support.
[0041] After the primary support of the upper step 4 is completed, the middle step 5 is excavated and primary support is carried out at the same time. When the excavation reaches the excavation boundary line 9 of the middle and lower steps and the primary support is constructed at the same time, the arch foot area 11 of the middle and lower steps is reinforced to enhance the bearing capacity of this key area and improve the stability of the primary support.
[0042] After the primary support of the middle step 5 is completed, the lower step 6 is excavated and primary support is carried out simultaneously. When the excavation reaches the invert arch 7 and the primary support is constructed to the invert arch 7, the invert arch steel arch frame is laid above the invert arch 7, and the two ends of the invert arch steel arch frame are fixedly connected to the primary support. At the same time, the invert arch foot area 12 is reinforced to comprehensively improve the bearing capacity of the bottom structure. The connection between the invert arch steel arch frame and the primary support forms a closed loop of the support system, which improves the overall stability of the support system.
[0043] In one embodiment, the monitoring and analysis of tunnel blasting vibration is performed using a blasting vibration detection system. The blasting vibration velocity is controlled within the allowable value of the blasting procedure through the blasting vibration detection system. The maximum blasting vibration velocity of the lining structure with initial support during the excavation of the upper bench 4 is effectively controlled within 20 cm / s. The blasting vibration velocity of the lower bench 6 is effectively controlled within 15 cm / s.
[0044] More specifically, the blasting vibration detection system includes a triaxial intelligent sensor and analysis software. The triaxial intelligent sensor is installed on the lining to monitor and collect blasting stress wave data; the analysis software is connected to the triaxial intelligent sensor to perform real-time analysis and processing of the collected blasting stress wave data. The triaxial intelligent sensor employs distributed, unattended online monitoring capabilities; the analysis software has functions such as oscilloscope analysis, batch data download, data playback, blasting characteristic analysis, and blasting prediction. Through analysis by the software, subsequent blasting design parameters are adjusted and optimized in a timely manner, minimizing the use of blasting-related materials while meeting the blasting excavation requirements and keeping the blasting vibration velocity within the allowable values of the blasting regulations.
[0045] In one embodiment, the reinforcement of the arch foot area 12 of the invert arch includes: a diagonal bracing steel frame, one end of which is connected to the invert arch steel arch frame on the invert arch 7, and the other end is connected to the primary support. By increasing the diagonal bracing steel frame, the load on the arch foot area 12 of the invert arch is distributed, the stress-bearing area is increased, and the effect of expanding the arch foot is achieved.
[0046] More specifically, the angle between the diagonal bracing steel frame and the straight wall is 60°.
[0047] In one embodiment, the reinforcement method for the upper and middle step arch foot area 10 is as follows: The upper and middle step arch foot area 10 is partially enlarged and excavated; after the enlarged excavation and hazard removal, a steel arch frame is installed; after the steel arch frame is installed, steel pipes are drilled perpendicular to the rock surface; after the steel pipes are installed, grout is injected into the inside of the steel pipes, and the steel pipes are welded to the steel arch frame. The steel arch frame is made of I-beams; in principle, the steel pipes perpendicular to the rock surface should also be perpendicular to the I-beams to fully utilize the effect of the steel frame in reinforcing the foundation bearing capacity. The foundation bearing capacity of the upper and middle step arch foot area 10 is improved by partially enlarging the excavation and installing the steel arch frame; the use of steel pipe grouting reinforcement of the arch frame replaces the traditional anchor bolt reinforcement, enhancing the foundation bearing capacity of the anchor bolts and reducing the tensile force that causes longitudinal cracks in the tunnel; simultaneously, the bearing capacity of the primary support in the upper and middle step arch foot area 10 and the stability of the primary support structure are improved; and sufficiently high foundation bearing capacity is provided to resist the high-intensity loads caused by the local instability of the soft and loose rock mass area after large-section excavation.
[0048] And / or, the angle between the steel pipe and the rock surface being drilled is 10° below the horizontal.
[0049] In one embodiment, the reinforcement method for the lower and middle bench arch foot area 11 is as follows: The lower and middle bench arch foot area 11 is partially enlarged and excavated; after the enlarged excavation and hazard removal, a steel arch frame is installed; after the steel arch frame is installed, steel pipes are drilled perpendicular to the rock surface; after the steel pipes are installed, grout is injected into the inside of the steel pipes, and the steel pipes are welded to the steel arch frame. The steel arch frame is made of I-beams; in principle, the steel pipes perpendicular to the rock surface should also be perpendicular to the I-beams to fully utilize the effect of the steel frame in reinforcing the foundation bearing capacity. The foundation bearing capacity of the lower and middle bench arch foot area 11 is improved by partially enlarging the excavation and installing the steel arch frame; the use of steel pipe grouting reinforcement of the arch frame replaces the traditional anchor bolt reinforcement, enhancing the foundation bearing capacity of the anchor bolts and reducing the tensile force that causes longitudinal cracks in the tunnel; simultaneously, the bearing capacity of the primary support in the lower and middle bench arch foot area 11 and the stability of the primary support structure are improved; and sufficiently high foundation bearing capacity is provided to resist the high-intensity loads caused by the local instability of the soft and loose rock mass area after large-section excavation.
[0050] And / or, the angle between the steel pipe and the rock surface being drilled is 10° below the horizontal.
[0051] In one embodiment, the reinforcement of the arch foot area 12 of the invert arch includes: drilling holes perpendicular to the downward direction of the invert arch 7 and holes inclined downwards from the invert arch 7 at the ends of the invert arch steel arch frame; installing steel pipes in the holes; grouting inside the steel pipes after installation, and welding the steel pipes to the invert arch steel arch frame. The invert arch steel arch frame is made of I-beams. By using steel pipe grouting reinforcement to reinforce the arch foot instead of traditional anchor bolt reinforcement, the bearing capacity of the anchor bolt foundation is improved, and the tensile force that causes longitudinal cracks in the tunnel is reduced; at the same time, the bearing capacity of the primary support in the arch foot area 12 of the invert arch and the stability of the primary support structure are improved. By providing sufficiently high foundation bearing capacity, the high-strength load caused by local instability in the soft and loose rock mass area after large-section excavation is resisted.
[0052] A tracked self-propelled down-the-hole drill was used. Before drilling, the positioning and layout of the invert arch I-beams were carried out. Two holes were drilled for each I-beam: one located directly below the I-beam, perpendicular to invert arch 7, with a depth of 9m; the other close to the foot of the stepped arch, at a 45° angle downwards from the horizontal, with a depth of 8.7m. Drilling was carried out after the excavation and shotcreting of invert arch 7 to avoid prolonged exposure of invert arch 7. During drilling, the I-beams on the other side of invert arch 7 could be constructed simultaneously, shortening the initial support closure time and maximizing efficiency. After drilling, the holes were immediately cleaned with high-pressure air hoses and the openings were sealed to prevent debris from falling into the holes.
[0053] Drilling was carried out directly from the bottom of the cable trench for the already formed section of the invert arch 7, with a drilling depth of 8.7m. One pipe was drilled at a 45° angle downwards to the horizontal, and the other was drilled at a 90° angle perpendicular to invert arch 7. The steel pipes were welded to the invert arch I-beams to form an integrated load-bearing system. Grouting reinforcement was carried out immediately after the steel pipes were installed, using a 1:1 (mass ratio) cement grout. The initial grouting pressure was 0.5MPa, and the termination pressure was 2MPa. Grouting was stopped after the grout overflowed from the borehole. During the grouting process, changes in grouting pressure and grout pump discharge rate were constantly monitored to analyze the grouting situation and prevent pipe blockage, grout leakage, and grout failure. After the grouting of the inner circulating steel pipes was completed, a secondary grouting was required to ensure that the grout inside the pipes was saturated.
[0054] For the unfinished section of the invert arch 7, steel pipes are first drilled and installed in the arch foot area 12 of the invert arch. The parameters and angles of the steel pipes are consistent with those of the formed section of the invert arch. Grouting is carried out immediately after the steel pipes are installed. Then, the invert arch I-beams are constructed, and the steel pipes are tightly welded to the invert arch I-beams. In principle, the steel pipes perpendicular to the invert arch 7 should be located directly below the I-beams to fully utilize the effect of the steel frame in reinforcing the bearing capacity of the foundation.
[0055] By setting holes at different angles at the ends of the invert arch steel frame and installing steel pipes for grouting, the overall stability of the invert arch foot area 12 was further enhanced, effectively preventing structural damage caused by load concentration, and improving the synergistic stress-bearing performance of the invert arch 7 and the primary support. This reinforcement method forms a three-dimensional support system through multi-angle anchoring, significantly improving the deformation resistance of the invert arch structure under complex geological conditions.
[0056] In one embodiment, the steel pipe is a seamless φ89×6mm pipe with a pointed bottom to ensure fast insertion speed and grouting quality. The pipe body has grout holes with a diameter of 12mm and a spacing of 30cm, arranged in a staggered pattern. A 30cm long, grout-stopping section without grout holes is provided at the tail end of the pipe. The steel pipe is installed using a manual-assisted mechanical method. After the pipe angle is adjusted to match the holes, the pipe will quickly enter the hole under gravity, resulting in high installation efficiency. The 30cm grout-stopping sections of the steel pipe are longitudinally connected by channel steel strips, and these sections are ultimately cast into the trench walls on both sides of the cable trench.
[0057] More specifically, the reinforcing steel pipe of the water outlet section in the arch foot area 12 of the invert arch is reinforced by grouting with a two-component grout. The two-component grout is mixed in a specific ratio and then solidifies rapidly through a chemical reaction to form a stone-like grouting material. This material can quickly seal cracks in the rock mass and cut off water flow channels, thus achieving rapid water stoppage while also reinforcing the surrounding rock mass.
[0058] In one embodiment, the blasting vibration buffer zone consists of multiple energy release holes 3 located at the interface between the weak and loose rock mass zone 2 and the hard rock mass zone 1; and / or, the blasting vibration buffer zone is excavated mechanically. During blasting, the energy release holes 3 can unload a portion of the energy generated by the blast, reducing the impact and disturbance of the blast on the surrounding rock, and facilitating the demolition work of mechanical equipment in this area.
[0059] More specifically, the energy release holes 3 are drilled using a pneumatic rock drill; the energy release holes 3 are arranged in a quincunx pattern with a spacing of 40cm, and the hole diameter is 42mm and the hole depth is 4m.
[0060] In one embodiment, the method further includes active reinforcement of the loosened surrounding rock. The active reinforcement method involves: based on the test results of the loosened surrounding rock zone, driving hollow grouting anchors into the loosened surrounding rock, and reinforcing the loosened surrounding rock by grouting through the hollow grouting anchors. The optimized arrangement of the hollow grouting anchors can form a combined anchor-grouting reinforcement zone around the loosened surrounding rock zone.
[0061] The hollow grouting anchor bolts are prestressed hollow grouting anchor bolts. By applying pre-stress to the anchor bolts, radial compressive stress is transmitted to the surrounding rock, pre-constraining the elastic-plastic deformation of the surrounding rock after excavation, inhibiting the convergence and settlement of the surrounding rock into the tunnel cavity, and preventing further expansion of the loose zone of the surrounding rock. Combined with the reinforcement of hollow grouting, the integrity of the surrounding rock is improved. At the same time, together with the steel arch frame, initial support, and arch foot area reinforcement, a stable support system is formed to effectively curb the instability of the surrounding rock and the generation of lining cracks, ensuring the safety and quality of tunnel construction.
[0062] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.
Claims
1. A method for excavating and constructing large-section tunnels in complex geological conditions, characterized in that, include: S1. According to the surrounding rock grade, the tunnel face is divided into at least one hard rock mass area (1) and at least one soft and loose rock mass area (2). A blasting vibration buffer zone is set at the end of the soft and loose rock mass area (2) near the hard rock mass area (1). Blasting excavation is used for the hard rock mass area (1) and mechanical excavation is used for the soft and loose rock mass area (2). When blasting is used to excavate in hard rock mass area (1), the tunnel blasting vibration is monitored and analyzed, the blasting parameters are optimized, and the blasting vibration velocity is controlled within the allowable value of the blasting procedure. S2. Measures to enhance the bearing capacity of the arch foot should be taken for the surrounding rock after excavation; The optimization of blasting parameters includes at least one of the following: multi-stage segmented blasting design, adjustment of explosive dosage, optimization of borehole distribution, and optimization of the number of boreholes. Among them, the multi-stage segmented blasting design refers to dividing the hard rock mass area (1) into multiple areas, and detonating the side away from the soft and loose rock mass area (2) first to form the free face in sequence; When designing multi-stage segmented blasting, the hard rock mass area (1) is divided into upper bench (4), middle bench (5), lower bench (6) and invert (7); it is excavated in sequence from top to bottom. When excavating the upper step (4), the primary support is constructed at the same time; when the excavation reaches the excavation boundary line (8) of the upper middle step and the primary support is constructed at the same time, the arch foot area (10) of the upper middle step is reinforced. After the primary support of the upper step (4) is completed, the middle step (5) is excavated and primary support is carried out at the same time; when the excavation reaches the excavation boundary line (9) of the middle and lower steps and the primary support is constructed to the excavation boundary line (9) of the middle and lower steps, the arch foot area (11) of the middle and lower steps is reinforced. After the primary support of the middle step (5) is completed, the lower step (6) is excavated and primary support is carried out at the same time; when the excavation reaches the invert arch (7) and the primary support is constructed to the invert arch (7) at the same time, the invert arch steel arch frame is laid above the invert arch (7) and the two ends of the invert arch steel arch frame are fixedly connected to the primary support; at the same time, the invert arch foot area (12) is reinforced; the reinforcement of the invert arch foot area (12) includes: drilling holes perpendicular to the invert arch (7) downward and holes inclined to the invert arch (7) downward respectively at the ends of the invert arch steel arch frame; steel pipes are installed in the holes; after the steel pipes are installed, grout is injected into the inside of the steel pipes and the steel pipes are welded to the invert arch steel arch frame; The reinforcement method of the upper middle step arch foot area (10) is as follows: the upper middle step arch foot area (10) is partially expanded and excavated, and steel arch frame is installed after the expansion and hazard removal; after the steel arch frame is installed, steel pipe is installed by drilling holes perpendicular to the rock surface; after the steel pipe is installed, grout is injected into the inside of the steel pipe, and the steel pipe is welded to the steel arch frame. The reinforcement method for the middle and lower step arch foot area (11) is as follows: the middle and lower step arch foot area (11) is partially expanded and excavated, and steel arch frame is installed after the expansion and hazard removal; after the steel arch frame is installed, steel pipe is installed by drilling holes perpendicular to the rock surface; after the steel pipe is installed, grout is injected into the inside of the steel pipe, and the steel pipe is welded to the steel arch frame. It also includes active reinforcement of loosened surrounding rock; the active reinforcement method is as follows: based on the test results of the loosened surrounding rock zone, hollow grouting anchor rods are driven into the loosened surrounding rock, and the loosened surrounding rock is reinforced by grouting the hollow grouting anchor rods.
2. The method for excavating and constructing a large-section tunnel in complex geological conditions according to claim 1, characterized in that, The reinforcement of the arch foot area (12) of the inverted arch includes: a diagonal bracing steel frame, one end of which is connected to the inverted arch steel frame on the inverted arch (7), and the other end is connected to the primary support.
3. The method for excavating and constructing a large-section tunnel in complex geological conditions according to claim 1, characterized in that, The reinforcing steel pipe of the arch foot area (12) of the inverted arch is reinforced by grouting with double liquid grout.
4. The method for excavating and constructing a large-section tunnel in complex geological conditions according to claim 1, characterized in that, The blasting vibration buffer zone consists of multiple energy release holes (3) set at the interface between the soft and loose rock mass area (2) and the hard rock mass area (1); and / or, the blasting vibration buffer zone is excavated mechanically.