High ground stress water-rich tunnel construction method

Abstract

The invention relates to a high ground stress water-rich tunnel construction method which comprises the following steps: excavating a tunnel by adopting a three-step method, and parallelly and synchronously erecting an upper step and deslagging a lower step; in the construction process, active supporting is conducted through quick excavation, quick supporting and quick closing, and a lower step and an inverted arch are excavated synchronously; in the primary support, profile steel is adopted for installing a steel frame, and a foot-lock anchor pipe is constructed; an inverted arch primary support steel frame and a lower step are constructed in the same cycle, and the distance between a closed ring and a tunnel face is not larger than 20 m; step height and steel frame spacing are adjusted in real time based on monitored and measured data; a three-dimensional drainage network is constructed, and drainage and pressure reduction of a water-rich section are conducted through roundabout parallel guide advanced high-position drainage and pressure reduction. Effective and reliable drainage can be carried out, meanwhile, the collapse risk of the tunnel face is reduced to the minimum, and the safety and stability of the construction process are guaranteed.

Description

Technical Field

[0001] The present application relates to the field of civil construction technology, and in particular to a method for constructing a high-ground stress water-rich tunnel. Background Art

[0002] During tunnel construction, in tunnel excavation and support under conditions of high ground stress and water-rich soft surrounding rock, the construction conditions are poor and the stratum stability is weak. The existing traditional excavation construction cannot guarantee the stability of the heading face.

[0003] At the same time, under the conditions of water-rich and weak surrounding rock, effective and reliable drainage methods need to be considered, as well as stable and effective support conditions.

[0004] How to carry out effective and reliable excavation in the stratum where the tunnel is located under high ground stress and water-rich soft surrounding rock conditions is a technical issue that needs to be considered. Summary of the Invention

[0005] The purpose of this application is to provide a high-stress water-rich tunnel construction method that can effectively and reliably drain water while reducing the risk of face collapse to a minimum, thereby ensuring the safety and stability of the construction process.

[0006] In order to achieve the above object, the present invention provides a high ground stress water-rich tunnel construction method, comprising the following steps:

[0007] The tunnel is excavated using the three-bench method, with the upper bench erection and lower bench slag removal carried out in parallel and synchronously;

[0008] During the construction process, active support was carried out through rapid excavation, rapid support and rapid closure, and the lower steps and inverts were excavated simultaneously;

[0009] Initial support uses steel sections to install the steel frame and constructs locking anchor pipes;

[0010] The primary support steel frame of the inverted arch is constructed in the same cycle as the lower step, and the closed ring is ≤20m away from the tunnel face;

[0011] Adjust the step height and steel frame spacing in real time based on monitoring and measurement data;

[0012] Construct a three-dimensional drainage network and discharge and reduce the pressure in water-rich areas through circuitous and level-diverting high-level discharge and pressure reduction.

[0013] In an optional embodiment, the inclined shaft section is a curved wall with an inverted arch structure, and the initial support steel frame uses H175 steel. Under the premise that the deformation of the surrounding rock can be controlled, large-sized steel is used and the spacing between the steel frames is increased. The deformation of the surrounding rock is controlled through stiffness graded support, and the spacing between the steel frames can be adjusted to adapt to the deformation rate.

[0014] In an optional embodiment, the inclined shaft invert arch and filling layer concrete are constructed in two layers, the first layer using dry hard concrete and the second layer using post-cast concrete.

[0015] In an optional embodiment, the fast excavation and fast support includes completing three cycles per day for a single-bay advance and two cycles per day for a double-bay advance, with the lowering of steps and invert arches being synchronized in a timely manner.

[0016] Quick closure includes controlling the initial support arch closure ring position within 20m from the tunnel face.

[0017] In an optional embodiment, a drainage ditch system is formed by double side ditches and a central ditch, and the double side ditches are connected to the central ditch through a transverse water diversion pipe;

[0018] The three-dimensional drainage network includes annular blind pipes and longitudinal blind pipes arranged behind the lining. The annular blind pipes include arch wall annular blind pipes. In water-rich areas, the arrangement density of the arch wall annular blind pipes is increased, and inverted arch annular blind pipes are arranged under the inverted arch. The inverted arch annular blind pipes and the arch wall annular blind pipes are arranged in a staggered manner.

[0019] The longitudinal blind pipe includes a Φ100 longitudinal permeable blind pipe set at the foot of the side wall, and a side wall drain pipe is set every 5-10m to introduce the water collected by the longitudinal blind pipe into the side ditch. The opening of the arch wall annular blind pipe bending into the side ditch is higher than the invert arch filling surface.

[0020] In an optional embodiment, in the open hole section, the straight side wall is topped with The longitudinal blind ditch and the straight side wall of the slope are backfilled with C20 concrete, and a 50cm thick sand and gravel filter layer is set on the top surface. The vertical blind pipe introduces the blind ditch water into the lining side ditch.

[0021] In an optional embodiment, the pressure on the tunnel face and side walls is reduced during construction. In front of the tunnel face, a length of 30-50m is driven. The advance drilling holes are drilled radially at the water outlet of the side wall with a length of 5 to 10 meters. Drainage hole.

[0022] In an optional embodiment, during the high-level water discharge and pressure reduction by the roundabout flat guide, a roundabout flat guide is added 30±2m away from one side of the main tunnel. The roundabout flat guide is constructed ahead of the main tunnel. The flat guide arch is about 2m higher than the top of the main tunnel, and a high-level roundabout guide pit is used for advance water drainage.

[0023] In an optional embodiment, the sidewall of the central groove is reserved Vertical corrugated pipes are arranged in a staggered manner with a longitudinal spacing of 3m. The pipe openings of the vertical corrugated pipes are ≥50cm higher than the bottom of the central ditch and are used to introduce pressurized water from the bottom of the invert into the central ditch.

[0024] In an optional embodiment, the inverted arch pressure relief holes are further included. After the inverted arch concrete is constructed, the holes are drilled downward along the filling surface, located 80 cm to the left and right of the center line, staggered on both sides, with a single-side spacing of 6 m, and avoiding construction joints ≥ 1 m;

[0025] The diameter of the inverted arch pressure relief hole is Φ108mm, and the depth is ≥0.5m into the bedrock. In the inverted arch filling, a groove is dug from the top of the inverted arch pressure relief hole to the central ditch. The groove is 11cm deep and 11cm wide below the cover plate. A Φ100 PVC pipe is installed in the groove to directly introduce the water gushing from the inverted arch pressure relief hole into the central ditch. After the PVC pipe is installed, the groove is backfilled with fine stone micro-expansive concrete of the same strength grade to the original filling top surface.

[0026] The high-stress water-rich tunnel construction method in this application can effectively control the deformation of the surrounding rock and shorten the closure time of the invert arch. The synchronous and parallel implementation of the three-step method can effectively improve the connection efficiency of each process and maximize the footage.

[0027] By effectively draining groundwater around the tunnel and at the base, the groundwater level and water pressure can be lowered, ensuring the safety of the tunnel structure and preventing conditions such as lining water pressure damage, uplift of the invert, and softening of the base. It can also effectively prevent sudden water inrush and ensure construction safety to the greatest extent possible. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 This is a schematic diagram of the process of the three-step construction method in this application. DETAILED DESCRIPTION

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all of the embodiments. Generally, the components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0031] In the description of this application, it should be noted that the terms "inner" and "outer" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or the orientations or positional relationships in which the product of this application is typically placed when in use. These terms are intended solely to facilitate the description of this application and simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first" and "second" and the like are used solely for distinction and should not be construed as indicating or implying relative importance.

[0032] It should also be noted that, in the description of this application, unless otherwise expressly specified or limited, the terms "disposed" and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to direct connections, indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0033] The high-stress water-rich tunnel construction method of the present invention is mainly improved from the traditional three-step construction method, and at the same time ensures operational safety during the construction process through all-round drainage.

[0034] The construction method for high-in-situ stress water-rich tunnels primarily involves two aspects, with drainage being essential for reliable tunnel excavation using the three-bench method. Specifically, the method employs a three-bench method for tunnel excavation, with the upper-bench erection and lower-bench slag removal performed simultaneously and in parallel.

[0035] During the construction process, active support is carried out through rapid excavation, rapid support and rapid closure, and the lower steps and invert arches are excavated simultaneously.

[0036] The initial support uses steel sections to install the steel frame and construct the locking foot anchor pipes. At the same time, through monitoring data, in order to control the deformation, the steel frame locking foot anchor pipes can be appropriately strengthened.

[0037] The initial supporting steel frame of the inverted arch is constructed in the same cycle as the lower step, and the closed ring is ≤20m away from the tunnel face.

[0038] Based on the monitoring and measurement data, the step height and steel frame spacing are adjusted in real time.

[0039] In order to be able to control large deformation, the structural form of the section is optimized in this application, and the double-lane inclined shaft section is optimized from a straight side wall bottom structure to a curved wall with an inverted arch structure.

[0040] At the same time, support parameters were strengthened, with the original I16 I-beams gradually optimized to I22 and H175 sections. Larger sections were used and the spacing between steel frames was increased, provided that surrounding rock deformation was controllable.

[0041] The deformation of the surrounding rock is controlled by stiffness graded support, while the spacing between steel frames can be adjusted to adapt to the deformation rate.

[0042] The inverted arch structure is optimized, and the inclined shaft inverted arch and filling layer concrete are constructed in two layers. The first layer uses dry hard concrete to quickly close the structure into a ring. The second layer uses post-cast concrete to ensure the flatness of the road surface and the passage of heavy-loaded vehicles.

[0043] The construction method in this application adheres to the principles of rapid excavation, rapid support, and rapid closure, achieving active support from a construction perspective. Rapid excavation and rapid support refers to completing three cycles per day for single-bay advances and two cycles per day for double-bay advances, with timely and synchronized progress of the lower bench and invert. Rapid closure refers to ensuring that the initial support invert closure loop is within 20 meters of the tunnel face.

[0044] During the construction process, the upper step height of the three-step method is preferably 2.8±0.1m, and the step length is 4.5-5m to ensure the stability of the tunnel face. The middle step height is 4.5m, and the lower step is excavated synchronously with the invert arch.

[0045] By fully utilizing the space above and below the steps on the tunnel face, the relationship between mucking and upper step arch installation processes was streamlined to achieve parallel operations. Through process design, repeated testing, and optimization and adjustment, the steps construction process was streamlined to: First, drilling and blasting: This includes construction preparation such as work platform hoisting, drilling, charging, and blasting, with the steps and inverts being raised and lowered simultaneously.

[0046] The second is ventilation and scraping: after the blasting and ventilation and smoke exhaust to meet the working environment standards, use an excavator to top the steps, remove dangerous rocks and scrape the scrap to the lower steps, and the upper steps meet the conditions for installing the steel frame.

[0047] The third step is mucking and arch erection on the upper steps. Loaders transport materials such as steel frames, steel mesh, and small advance pipes, as well as small equipment like welders and pneumatic drills, to the upper steps. The steel frame installation is organized and implemented on the upper steps. On the lower steps, loaders and dump trucks work together to remove mucking. Due to the height of the steps, the upper and lower steps separate the two processes of erecting the frame and mucking, ensuring operational safety.

[0048] Fourth, spray concrete on the upper steps and install the lower step steel frame. Once the lower step is mucking, spray concrete on the upper steps can begin. Simultaneously, the lower step steel frame is installed and the locking feet are installed. Ensure proper ventilation and worker safety during construction, and maximize parallel operations.

[0049] See also Figure 1 The three-step method mainly includes the following steps during construction:

[0050] 1) Clean the upper step face. The main purpose is: first, to clean the rebound shotcrete to create conditions for the next drilling cycle; second, to level the upper step site to create conditions for the positioning of the work platform.

[0051] Due to the presence and length of the steps, and the limited reach of the excavator's arm, it's impossible to remove the rebounded concrete at the bottom of the upper step. The following measures can be taken: First, strictly control the rebound rate of the shotcrete. Second, manually clean the top of the shotcrete while it's being sprayed. Third, lay an isolation layer, such as waterproofing, at the bottom of the upper step face. After the shotcrete is shotcreted, manually and mechanically remove the concrete to the middle step for disposal. Fourth, thoroughly remove the slag from the top of the upper step during the upper cycle slag removal process.

[0052] 2) Platform Positioning. Work can be performed using a work platform or core soil. The work platform must be transported to the upper step before work begins. Core soil can be reserved on the upper step as a working platform. Alternatively, a portion of the upper step can be left as slag and trimmed to create a platform for easier work. Alternatively, a simple, lightweight, on-site assembled work platform can be used and manually positioned.

[0053] 3) Measure, stake out, and clean the inverted arch. Mark the excavation line and blasthole locations, and use an excavator to clean the inverted arch slag.

[0054] 4) Drilling and Charging. Each step, including the invert, was drilled and charged simultaneously using a handheld pneumatic drill. The upper step was smooth blasting, with wedge-shaped cuts typically arranged in four pairs. The bottoms of the holes were 0.2-0.3 m apart, with the spacing between adjacent pairs of holes controlled at 50-90 cm. The spacing around the holes was 35-50 cm.

[0055] 5) Retreat the platform. After the upper step charging is completed, the work platform is moved out of the tunnel face. The work platform is moved to the middle step manually, and the excavator moves the work platform out of the tunnel face.

[0056] 6) Blasting operation: Connect all steps and detonate simultaneously.

[0057] 7) Ventilation and hazard removal: After the face blast, the ventilator should be used at high position to exhaust smoke and dust for 15 minutes, and manual and mechanical hazard removal should be carried out.

[0058] 8) Remove slag from the upper step. Remove the slag from the upper step to the lower step to provide conditions for the next process on the upper step.

[0059] While the excavator is removing slag from the upper steps, the slag can be discharged. While the excavator is removing the slag from the upper steps, the temporary road is repaired to prepare for the transportation of the work platform, stand and other related materials.

[0060] 9) Position the workbench and transport support materials. Use an excavator to transport the workbench to the upper step. Materials such as the steel arch frame, anchor rods, small conduits, and steel mesh used for the upper step support should preferably be transported to the upper step by an excavator. A loader may also be used if safety is ensured.

[0061] 10) Slag removal. Load and transport the slag outside the tunnel. Two wheeled side dump loaders, one wheeled side dump loader and one excavator, or one wheeled side dump loader can be used to load the slag, and then dump trucks can be used to transport it outside the tunnel. While the slag is being removed, erect scaffolding, anchor bolts, and advance support are constructed on the middle step.

[0062] 11) Inverted arch cleaning. After the upper and lower steps are slag removed, proceed with the inverted arch slag excavation and check whether the inverted arch excavation dimensions for the current cycle are acceptable. The excavated inverted arch slag is piled to the rear side for later backfilling. At the same time, notify the shotcrete team to prepare.

[0063] 12) Lower step and inverted arch support. After the slag at the bottom of the inverted arch is cleared, the lower step and the primary support steel frame of the inverted arch are installed. The primary support steel frame of the inverted arch can be directly looped with the lower step as a circulating steel frame.

[0064] 13) Spray concrete on the inverted arch and lower steps. Spray concrete on the inverted arch first and then on the lower steps, and spray concrete from bottom to top to increase the setting time of the inverted arch concrete.

[0065] 14) Backfill the inverted arch with slag. Backfill the inverted arch with the slag reserved during the previous excavation.

[0066] 15) Retreat the platform. Move the work platform used during the erection process to the outside of the tunnel face. Manual labor and mechanical assistance will move the platform to the middle step, and the excavator will move the platform out of the tunnel face.

[0067] 16) Spray concrete on the middle and upper steps. The wet spraying manipulator is positioned close to the lower step to spray concrete. If the wet spraying manipulator cannot accommodate the space required for the three steps, the step length can be adjusted appropriately. Once this process begins, promptly notify the lower excavation team to prepare for the transition.

[0068] 17) The surrounding rock for mechanical excavation is typically soft. During excavation, first use an excavator to excavate the lower and middle steps for roadwork, then ascend to the middle step. Use a ripper or a specialized bucket for excavation to excavate the upper step, supplemented by manual work. After excavation is complete, move the excavated soil to the middle and lower steps. Then, move the steps and construction materials to the upper step arch. Continue excavating the middle and lower steps, carrying out arch erection and excavation operations in parallel with the upper and middle steps.

[0069] From the perspective of strengthening support, the steel frame adopts H175 steel with a yield strength of ≥345MPa. The steel frame spacing is 0.6m. When the deformation is greater than 5mm / d, the steel frame spacing is increased to 0.5m.

[0070] The arch foot is equipped with a 300mm×300mm×10mm steel bench, and the locking foot anchor pipe is increased to 4 Φ42mm anchor pipes with a length of 4m.

[0071] By synchronizing the installation of the upper step steel frame and the slag discharge of the lower step, the overlapping time of the synchronous operations can be made ≥70%, and the distance from the initial support and closure of the inverted arch to the ring is ≤18m from the tunnel face.

[0072] The three-step excavation construction method in the present invention can reduce the deformation of the surrounding rock by 40%, shorten the arch closure time by 30%, improve the process connection efficiency by 50%, and achieve a monthly advance of 45 meters, which is better than the 30 meters of the traditional operation method.

[0073] Based on the three-step construction method described above, effective drainage is also carried out throughout the present invention.

[0074] A drainage ditch system is formed by double side ditches and a central ditch, and the double side ditches and the central ditch are connected through horizontal water diversion pipes at intervals of 30m;

[0075] The three-dimensional drainage network includes annular blind pipes and longitudinal blind pipes set behind the lining. The annular blind pipes include arch wall annular blind pipes with a standard spacing of 10m. Permeable hose, wrapped in non-woven fabric. In water-rich areas, increase the density of arch wall annular blind pipes, increase the standard spacing to 5m, and install inverted arch annular blind pipes under the inverted arch, staggering the inverted arch annular blind pipes with the arch wall annular blind pipes.

[0076] The longitudinal blind pipe includes a Φ100 longitudinal permeable blind pipe set at the foot of the side wall, and a side wall drain pipe is set every 5-10m to introduce the water collected by the longitudinal blind pipe into the side ditch. The opening of the arch wall annular blind pipe bending into the side ditch is higher than the filling surface of the inverted arch to prevent clogging.

[0077] Special treatment is carried out in the Mingdong section, and the top of the straight side wall is set The longitudinal blind ditch and the straight side wall of the slope are backfilled with C20 concrete, and a 50cm thick sand and gravel filter layer is set on the top surface. The vertical blind pipe introduces the blind ditch water into the lining side ditch.

[0078] During the construction process, the pressure on the face and side walls is reduced. In front of the face, a length of 30-50m is set. The advanced drilling holes are used to directly drain water and reduce the water level and pressure in front of the face.

[0079] At the water outlet point of the side wall, the radial length is 5 to 10 meters. Drain holes: Targetedly drain concentrated water from the side walls to reduce local water pressure.

[0080] In the process of high-level water discharge and pressure reduction by detour flat guide, a detour flat guide is added 30±2m away from one side of the main tunnel. The detour flat guide is constructed ahead of the main tunnel. The arch of the flat guide is about 2m higher than the top of the main tunnel. A high-level detour pilot pit is used for advance water drainage.

[0081] By utilizing the funnel effect formed by the high-level pilot pit, the large-scale groundwater above and in front of the main tunnel can be discharged in advance through the horizontal guide pit, which significantly reduces the groundwater level in the main tunnel area and creates favorable low-water pressure conditions for grouting reinforcement of the main tunnel, such as curtain grouting.

[0082] Center groove side wall reserved Vertical corrugated pipes are arranged in a staggered manner with a longitudinal spacing of 3m. The pipe openings of the vertical corrugated pipes are ≥50cm higher than the bottom of the central ditch and are used to introduce pressurized water from the bottom of the invert into the central ditch.

[0083] In order to solve the problem of pressurized water at the bottom of the inverted arch in a targeted manner, drainage is also carried out through pressure-reducing holes at the bottom of the tunnel, including the pressure-reducing holes of the inverted arch. After the concrete of the inverted arch is completed, the holes are drilled downward along the filling surface, located 80 cm left and right of the center line, and arranged alternately on both sides with a single-side spacing of 6 m, avoiding construction joints ≥ 1 m.

[0084] The diameter of the inverted arch pressure relief hole is Φ108mm, and the depth is ≥0.5m into the bedrock. A groove is dug from the top of the inverted arch pressure relief hole to the central ditch in the inverted arch filling. The groove is 11cm deep and 11cm wide below the cover plate. A Φ100PVC inverted arch annular blind pipe is installed in the groove to directly introduce the water gushing from the inverted arch pressure relief hole into the central ditch. After the PVC pipe is installed, the groove is backfilled with fine stone micro-expansive concrete of the same strength grade to the original filling top surface to prevent water seepage through shrinkage gaps.

[0085] The drainage system in this invention systematically constructs a three-dimensional drainage network from the lining perimeter (circumferential and longitudinal blind pipes) to drainage ditches (lateral and central ditches) and finally to the basement (blind pipes under inverts and pressure-reducing holes). Blind pipes are densely packed in water-rich areas, with dedicated blind pipes under inverts and an advanced pressure-reducing hole system to address the pressure-bearing water problem at the basement. Pre-drilling, radial drilling, and circuitous flat guides are used to reduce pressure at the tunnel face, localized water outlets on the sidewalls, and in water-rich sections.

[0086] It not only passively collects seepage water (such as blind pipes), but also emphasizes active pressure reduction (advanced holes, radial holes, circuitous flat guides, and pressure reduction holes), especially during the construction period and for high-pressure water in the base.

[0087] Blind pipes are wrapped with non-woven fabric to prevent clogging. Drainage orifices are elevated above the filling surface / ditch bottom to prevent backflow and clogging. Circumferential blind pipes are staggered to optimize drainage paths. Pressure-reducing holes are staggered to avoid joints. The depth of the water diversion channel ensures smooth water flow. Micro-expansive concrete is used for backfill to prevent seepage. A filter layer is designed in the open tunnel section to prevent soil erosion.

[0088] By effectively reducing the surrounding rock and base water pressure, the risks of lining cracking, uplift of the invert, sudden water inrush, and base instability are greatly reduced, ensuring the long-term safe operation of the tunnel. Advanced drainage and pressure reduction (advanced drilling and circuitous leveling) provide the conditions for safe excavation and effective grouting.

[0089] By combining permanent drainage facilities with active pressure reduction measures during the construction period, special attention is paid to solving the problem of base pressure water, which is the most harmful to the tunnel structure, and it plays a key role in ensuring the safety and quality of tunnel projects in water-rich strata.

[0090] Combining a systematic design approach with layers and levels, the entire drainage system is divided into four subsystems: first, the conventional post-lining drainage system, which serves as the basic defense line; then, the advance drainage system consisting of face advance drainage and circuitous pilot pit drainage; and finally, the inverted arch drainage system, which is specifically designed to address the most difficult problem of basement pressure water.

[0091] The present invention adopts differentiated blind pipe arrangement density according to different hydrogeological conditions. The high-level horizontal guide uses the principle of gravity drainage to naturally lower the water level. The design angle of the inverted arch pressure relief hole effectively solves the technical problem of inverted arch floating in tunnel engineering through the triple guarantee of drilling + pipe + groove.

[0092] A three-dimensional grid layout of circumferential and longitudinal blind pipes and staggered arrangement of various drainage pipes avoids stress concentration. All drainage outlets are strictly above the bottom of the receiving ditch to prevent backflow. Fine stone micro-expansive concrete backfill ensures structural strength while preventing shrinkage and leakage.

[0093] By combining traditional blind drainage pipes with active pressure-reduction measures, a comprehensive system of drainage, pressure reduction, release, and diversion has been established, providing valuable insights into managing high-pressure tunnels. In particular, the measures addressing water pressure in invert arches transcend the limitations of traditional tunnel drainage, which primarily focuses on the side walls and arch crown.

[0094] The present invention can effectively drain groundwater around the tunnel and at the base, lower the groundwater level and water pressure, ensure the safety of the tunnel structure, prevent lining water pressure damage, uplift of the invert, softening of the base, and prevent sudden water gushing to ensure construction safety.

[0095] The comprehensive effect is that the groundwater level in the main tunnel area dropped by 3m, the risk of arch foot softening was reduced by 60%; the peak water pressure of the invert arch was ≤0.2MPa (traditional 0.5MPa), and the structural leakage rate was reduced to below 5%.

[0096] It should be noted that, unless there is any conflict, the features in the embodiments of this application can be combined with each other.

[0097] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A high ground stress water-rich tunnel construction method, characterized in that: The following steps are involved: The tunnel is excavated using the three-bench method, with the upper bench erection and lower bench slag removal carried out in parallel and synchronously; During the construction process, active support was carried out through rapid excavation, rapid support and rapid closure, and the lower steps and inverts were excavated simultaneously; The initial support uses steel sections to install the steel frame and constructs locking anchor pipes; The primary support steel frame of the inverted arch is constructed in the same cycle as the lower step, and the closed ring is ≤20m away from the tunnel face; Adjust the step height and steel frame spacing in real time based on monitoring and measurement data; Construct a three-dimensional drainage network and discharge and reduce the pressure in water-rich areas through circuitous and level-diverting high-level water discharge and pressure reduction.

2. The high ground stress water-rich tunnel construction method according to claim 1, characterized in that: The inclined shaft section is a curved wall with an inverted arch structure. The initial support steel frame uses H175 steel. Under the premise that the surrounding rock deformation can be controlled, large-size steel is used and the spacing between steel frames is increased. The surrounding rock deformation is controlled through stiffness graded support, and the spacing between steel frames can be adjusted to adapt to the deformation rate.

3. The high ground stress water-rich tunnel construction method according to claim 1, characterized in that: The inclined shaft invert arch and filling layer concrete are constructed in two layers, the first layer uses dry hard concrete, and the second layer uses post-cast concrete.

4. The high ground stress water-rich tunnel construction method according to claim 1, characterized in that: Fast excavation and support include completing three cycles per day for a single-bay advance and two cycles per day for a double-bay advance, with timely and synchronous follow-up of lower steps and invert arches; Quick closure includes controlling the initial support arch closure ring position within 20m from the tunnel face.

5. The high ground stress water-rich tunnel construction method according to claim 1, characterized in that: A drainage ditch system is formed by double side ditches and a central ditch, and the double side ditches and the central ditch are connected through a horizontal water diversion pipe; The three-dimensional drainage network includes annular blind pipes and longitudinal blind pipes arranged behind the lining. The annular blind pipes include arch wall annular blind pipes. In water-rich areas, the arrangement density of the arch wall annular blind pipes is increased, and inverted arch annular blind pipes are arranged under the inverted arch. The inverted arch annular blind pipes and the arch wall annular blind pipes are arranged in a staggered manner. The longitudinal blind pipe includes a Φ100 longitudinal permeable blind pipe set at the foot of the side wall, and a side wall drain pipe is set every 5-10m to introduce the water collected by the longitudinal blind pipe into the side ditch. The opening of the arch wall annular blind pipe bending into the side ditch is higher than the invert arch filling surface.

6. The high ground stress water-rich tunnel construction method according to claim 5, characterized in that: In the open tunnel section, a φ100 longitudinal blind ditch is set on the top of the straight side wall, the straight side wall range of the slope is backfilled with C20 concrete, a 50cm thick sand and gravel filter layer is set on the top surface, and a φ50 vertical blind pipe is used every 5-10m to introduce the blind ditch water into the lining side ditch.

7. The high ground stress water-rich tunnel construction method according to claim 5, characterized in that: During the construction process, the pressure on the face and side walls is reduced. In front of the face, advance drill holes with a length of 30-50m and a diameter of 89-108mm are drilled. Drain holes with a length of 5-10m and a diameter of 42-89mm are drilled radially at the water outlet points of the side walls.

8. The high ground stress water-rich tunnel construction method according to claim 5, characterized in that: In the process of high-level water discharge and pressure reduction by detour flat guide, a detour flat guide is added 30±2m away from one side of the main tunnel. The detour flat guide is constructed ahead of the main tunnel. The arch of the flat guide is 2m higher than the top of the main tunnel, and a high-level detour pilot pit is used for advance water drainage.

9. The high ground stress water-rich tunnel construction method according to claim 5, characterized in that: Center groove side wall reserved Vertical corrugated pipes are arranged in a staggered manner with a longitudinal spacing of 3m. The pipe openings of the vertical corrugated pipes are ≥50cm higher than the bottom of the central ditch and are used to introduce pressurized water from the bottom of the invert into the central ditch.

10. The high ground stress water-rich tunnel construction method according to claim 5, characterized in that: It also includes inverted arch pressure relief holes. After the inverted arch concrete is completed, the holes should be drilled downward along the filling surface, located 80 cm to the left and right of the center line, staggered on both sides, with a single-side spacing of 6 m, and avoid construction joints ≥ 1 m; The diameter of the inverted arch pressure relief hole is Φ108mm, and the depth is ≥0.5m into the bedrock. In the inverted arch filling, a groove is dug from the top of the inverted arch pressure relief hole to the central ditch. The groove is 11cm deep and 11cm wide below the cover plate. A Φ100 PVC pipe is installed in the groove to directly introduce the water gushing from the inverted arch pressure relief hole into the central ditch. After the PVC pipe is installed, the groove is backfilled with fine stone micro-expansive concrete of the same strength grade to the original filling top surface.

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