Large-section tunnel supporting structure of deep sandy gravel covering layer and excavation method

Abstract

The invention provides a large-section tunnel supporting structure of a deep sandy gravel covering layer and an excavation method, and relates to the technical field of building construction.The large-section tunnel supporting structure of the deep sandy gravel covering layer comprises a mountain advanced reinforcing module, a high-pressure spraying reinforcing body and a grouting reinforcing body, the high-spraying reinforcing bodies are vertically arranged outside the side lines of the two sides of the large-section cavern respectively, and the multiple grouting reinforcing bodies are vertically and evenly distributed in an excavation area of the large-section cavern; the indoor support module comprises a top arch opposite-penetrating anchor cable, a side wall opposite-penetrating anchor cable and an advance support body; the forepoling body is arranged on the top arch portion of the large-section cavern in the tunneling direction of the large-section cavern and used for reinforcing the top arch portion of the large-section cavern in advance before the large-section cavern is excavated. Compared with the prior art, the problems that collapse and roof collapse are likely to happen to the excavation face in the construction process can be solved.

Description

Technical Field

[0001] The invention relates to the technical field of building construction, and in particular to a large-section tunnel support structure with a thick sand and gravel overlay and an excavation method. Background Art

[0002] A large-section tunnel with a thick gravel cover layer refers to a large-section tunnel excavated under a thick gravel layer below the surface. Due to the constraints of environmental protection, confidentiality, cost and other factors, the large-section cavern has to be entered by using the cover layer, thereby reducing the environmental damage, slope stability, capital investment and other problems caused by open excavation of a large amount of cover layer.

[0003] However, after research, the applicant found that the sand and gravel stratum was affected by groundwater, resulting in an extremely unstable excavation surface that was prone to landslides, roof falls, and other phenomena. Summary of the invention

[0004] In order to improve the problem of landslide and roof collapse on the excavation surface during the construction process, the present application provides a large-section tunnel support structure and excavation method with a thick gravel overburden layer.

[0005] In the first aspect, the present application provides a large-section tunnel support structure with a thick gravel overburden layer, which adopts the following technical solution: A large-section tunnel support structure in a thick gravel overburden layer comprises: a mountain advance reinforcement module, comprising a high-pressure jet reinforcement body and a grouting reinforcement body, wherein the high-pressure jet reinforcement body is vertically arranged outside the side lines of both sides of the large-section cavern, and the grouting reinforcement body is vertically evenly distributed in a plurality of lines in the excavation area of ​​the large-section cavern; an indoor support module, comprising a top arch through-anchor cable, a side wall through-anchor cable and an advance support body, wherein the top arch through-anchor cable is vertically arranged above the large-section cavern. There are multiple anchor cables, and the lower ends of the top arch penetrating anchor cables are located at the top arch part of the large-section cavern; multiple side wall penetrating anchor cables are horizontally arranged outside the side lines of both sides of the large-section cavern, and one ends of the side wall penetrating anchor cables are located at the side line part of the large-section cavern; the advanced support body is arranged at the top arch part of the large-section cavern along the excavation direction of the large-section cavern, so as to reinforce the top arch part of the large-section cavern in advance before the excavation of the large-section cavern.

[0006] Preferably, a plurality of groups of first anchoring caverns are evenly distributed horizontally above the large-section cavern, and one group of the first anchoring caverns corresponds to one of the high-pressure jet reinforcement bodies; and one end of the high-pressure jet reinforcement body away from the large-section cavern is located in the first anchoring cavern.

[0007] Preferably, the distance that the top end of the high-pressure spraying reinforcement body is higher than the top arch elevation of the large-section cavern is greater than or equal to the cave height distance of the large-section cavern; and / or, the bottom end of the high-pressure spraying reinforcement body extends 3m~5m below the excavation bottom plate of the large-section cavern.

[0008] Preferably, adjacent first anchoring caverns are connected with a connecting cavern, the end of the grouting reinforcement body away from the large-section cavern is located in the connecting cavern, and the top end of the top arch through-through anchor cable is also located in the connecting cavern.

[0009] Preferably, the distance that the top end of the grouting reinforcement body is higher than the top arch elevation of the large-section cavern is greater than or equal to the cave height distance of the large-section cavern; and / or, the bottom end of the grouting reinforcement body extends 1.5m to 2.5m below the excavation bottom plate of the large-section cavern.

[0010] Preferably, multiple groups of second anchoring caverns are provided on both sides of the large-section cavern, and one group of the second anchoring caverns corresponds to one of the side wall cross-linking anchor cables, and one end of the side wall cross-linking anchor cable away from the large-section cavern is located in the second anchoring cavern; along the vertical direction, adjacent second anchoring caverns are staggered; and / or the vertical spacing between adjacent second anchoring caverns is 6m to 8m.

[0011] Preferably, the advance support body includes a supporting tube body and a steel frame, the supporting tube body has multiple evenly distributed arc lines along the top arch of the large-section cavern, and the length direction of the supporting tube body is consistent with the excavation direction of the large-section cavern; the steel frame is arranged on the periphery of the large-section cavern along the outer contour of the large-section cavern, and multiple groups of the steel frames are arranged at intervals along the excavation direction of the large-section cavern.

[0012] Preferably, the support tube body comprises a hollow outer tube, an extruded inner column, an axial limiter and a radial limiter; wherein, a slot for inserting the extruded inner column is axially provided inside the hollow outer tube, and the two ends of the slot are an open end and a sealed end respectively; the axial limiter is movably arranged at the sealed end of the support tube body close to the slot, and the moving direction of the axial limiter is perpendicular to the length direction of the support tube body, and during the movement of the extruded inner column along the length direction of the slot, the axial limiter can be moved out of the hollow outer tube and extended into the mountain soil layer outside the hollow outer tube under the extrusion action of the extruded inner column; the radial limiter is movably arranged in the axial limiter, and the moving direction of the radial limiter is parallel to the length direction of the support tube body, and after the axial limiter is moved into place, when the extruded inner column continues to move in the slot, the radial limiter can be moved out of the axial limiter and extended into the mountain soil layer outside the axial limiter under the extrusion action of the extruded inner column.

[0013] Preferably, the axial limiting member comprises a first limiting portion and a first spring, a movable cavity vertically connected to the slot is provided on the side wall of the hollow outer tube, the first limiting portion is slidably arranged in the movable cavity, the inner side wall of the movable cavity is connected and provided with a side groove, the first limiting portion is provided with a support block extending into the side groove, one end of the first spring is connected to the inner end wall of the side groove, and the other end is connected to the support block; the first limiting portion comprises a tip section, a straight section and an inclined section connected in sequence axially, when the first spring is in a natural state, the tip section is located in the movable cavity, and the inclined section extends into the slot; the inclined section has a first abutting inclined surface at one end facing the slot, and the front end of the extrusion inner column has a second abutting inclined surface opposite to the first abutting inclined surface, when the extrusion inner column is moved along the slot, the second abutting inclined surface can be slidably abutted with the first abutting inclined surface, so that the inclined section is pushed from the slot into the movable cavity under the extrusion action, and at the same time, the tip section extends out of the movable cavity and is inserted into the mountain soil layer; The radial limit member includes an abutment rod, a connecting rod, a plug-in rod and a second spring. The straight section is provided with an abutment channel, a connecting channel and a plug-in channel which are connected in sequence. The length direction of the connecting channel is consistent with the moving direction of the axial limit member. The abutment channel is vertically connected to the side of the connecting channel close to the tip section, and the plug-in channel is vertically connected to the side of the connecting channel close to the inclined section, and the abutment channel and the connecting channel are extended opposite to each other. The connecting rod is movably arranged in the connecting channel, the abutment rod is vertically connected to one end of the connecting rod and is slidably arranged in the abutment channel, and the plug-in rod is vertically connected to the other end of the connecting rod and is slidably arranged in the plug-in channel; the second spring is arranged in the connecting channel, and along the length direction of the slot, the second spring always has the function of moving the connecting rod away from the abutment channel. The tendency of pushing the channel side is so that when the second spring is in a natural state, the abutment rod is received in the abutment channel; the hollow outer tube is also provided with a branch groove parallel to the slot, and a branch rod is parallel to one side of the extruded inner column, and the branch rod is slidably inserted in the branch groove, wherein, when the second abutment slope moves along the slot and completely passes through the end opening of the moving cavity, the abutment channel moves from the moving cavity to the outside, and the end opening of the plug-in channel is directly opposite to the end opening of the branch groove in the axial direction of the support tube body, and the end of the branch rod is also directly opposite to the end of the plug-in rod, so that when the extruded inner column continues to move along the slot, the branch rod pushes the plug-in rod part into the connecting channel, and at the same time drives the abutment rod to extend from the end opening of the abutment channel and insert into the mountain soil layer.

[0014] In the second aspect, the present application provides a method for excavating a large-section tunnel in a thick gravel overburden layer, which adopts the following technical solution: A method for excavating a large-section tunnel in a thick gravel overburden layer is implemented based on the large-section tunnel support structure in a thick gravel overburden layer described in the above scheme, and comprises the following steps: The large-section cave excavation surface is divided into four modules, namely, a top arch module, a middle layer module, a lower layer module and a bottom plate protection layer module, wherein the top arch module is divided into five areas for construction, namely, I-1 layer, I-2 layer, I-3 layer, I-4 layer and I-5 layer; the middle layer module is divided into three areas for construction, namely, II-1 layer, II-2 layer and II-3 layer; the lower layer module is divided into three areas for construction, namely, III-1 layer, III-2 layer and III-3 layer; the bottom plate protection layer module is constructed last without partitioning; First, excavate the first anchor cavern and the second anchor cavern, and provide support at the same time; High-pressure grouting reinforcement is adopted, and high-pressure grouting is vertically sprayed downward from the first anchor cavern to the top arch side of the large-section cavern to form the high-pressure grouting reinforcement body; The grouting reinforcement body is reinforced by injecting cement grout after drilling holes, drilling holes horizontally from the second anchoring cavern toward the edge of the large-section cavern and injecting cement grout to form the grouting reinforcement body; Performing installation construction of advance support along the outer peripheral contour of the large-section cavern; The top arch module is excavated in the following order: excavation and support of layer I-1, excavation and support of layer I-2, construction of anchor cables for the side walls close to the top layer of the large-section cavern, excavation and support of layer I-3, excavation and support of layer I-4, excavation and support of layer I-5, and construction of anchor cables for the top arch; Excavate the middle layer module, and the excavation sequence is: excavation and support of layer II-1, excavation and support of layer II-2, construction of anchor cables for the side walls near the middle layer of the large-section cavern, and excavation and support of layer II-3; Excavating the lower layer module, the excavation sequence is: excavation and support of layer III-1, excavation and support of layer III-2, construction of anchor cables for side walls near the middle and lower layers of the large-section cavern, and excavation and support of layer III-3; Finally, the bottom plate protective layer module is excavated and supported as a whole.

[0015] The present invention has the following advantages and beneficial effects: The setting of the mountain advance reinforcement module, through the combination of high-pressure spray reinforcement and grouting reinforcement, can reinforce the surrounding strata in advance before tunnel excavation. The high-pressure spray reinforcement is arranged vertically outside the two side lines of the large-section cavern, which can strengthen the strata before excavation and prevent large-scale strata collapse and displacement, thereby effectively improving the safety during tunnel excavation. The uniform arrangement of grouting reinforcement in the excavation area further enhances the stability of the strata, reduces the softening of the soil caused by the influence of groundwater, and ensures that the strata will not be damaged on a large scale during tunnel excavation; The indoor support module further strengthens the support effect in the tunnel through the reasonable layout of the top arch through anchor cables, side wall through anchor cables and advance support bodies. The top arch through anchor cables are set at the top arch of the tunnel. Multiple vertically arranged anchor cables can not only improve the bearing capacity of the top arch, but also effectively share and transfer the pressure from the excavation surface and the surrounding soil, avoiding the roof collapse caused by insufficient support. The side wall through anchor cables are arranged horizontally on both sides of the tunnel. One end of multiple anchor cables is set at the edge of the large-section cavern, which can stabilize the side wall structure of the tunnel and prevent slope instability and landslides caused by changes in the excavation surface. In particular, the side wall anchor cables form an effective pulling effect through the through arrangement, further enhancing the stability of the side walls on both sides of the tunnel, improving the mutual restraint between the tunnel excavation surface and the surrounding soil, and avoiding cracking or damage to the side walls due to loose local strata or groundwater influence; The advance support body is arranged in the tunnel arch along the tunnel excavation direction, which plays a role in advance reinforcement. By reinforcing the arch in advance, the advance support body can effectively slow down or prevent the instability of the strata below the excavation surface, share the pressure of the arch in advance, ensure that the tunnel is not affected by excessive uneven stratum deformation during the excavation process, and significantly improve the construction safety and stability of the tunnel. Especially in deep gravel strata, the flow of groundwater and loose strata often pose a threat to tunnel stability. The design of the advance support body can pre-enhance the support force of the arch before excavation, avoiding accidents such as arch collapse caused by uneven excavation progress, and ultimately avoiding the problem of landslides and roof falls on the excavation surface during construction to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 It is a schematic diagram of the structure of some embodiments of the present application; Figure 2It is a schematic diagram of a module for displaying a large-section cavern in some embodiments of the present application; Figure 3 This is a schematic diagram of the structure of the support tube body used to show some embodiments of the present application. Figure 1 ; Figure 4 This is a schematic diagram of the structure of the support tube body used to show some embodiments of the present application. Figure 2 ; Figure 5 yes Figure 3 A magnified view of part A in FIG. Figure 6 yes Figure 4 Enlarged view of part B in .

[0018] The markings in the figure are: 100, mountain advance reinforcement module; 110, high-pressure jet reinforcement body; 120, grouting reinforcement body; 200, large-section cavern; 300, indoor support module; 400, top arch through anchor cable; 500, side wall through anchor cable; 600, advance support body; 610, support pipe body; 6110, hollow outer pipe; 6111, slot; 6112, movable cavity; 6113, side groove; 6114, branch groove; 6120, extruded inner column; 6121, second abutment slope; 6122, branch rod; 6130, axial limiter; 6131, first limiting part; 61311, tip section; 61312, straight section; 6131a, abutment channel; 6131b, connecting channel; 6131c, plug-in channel; 61313, inclined section; 61314, first abutment slope; 6132, first spring; 6140, radial limiting part; 6141, abutment rod; 6142, connecting rod; 6143, plug-in rod; 6144, second spring; 620, steel frame; 700, first anchoring cavern; 800, connecting cavern; 900, second anchoring cavern. DETAILED DESCRIPTION

[0019] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0020] The terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described here, and the objects distinguished by "first", "second", etc. are generally of one type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0021] In the related art, a large-section tunnel with a thick gravel cover usually refers to a large-section tunnel excavated under the condition that there is a thick gravel layer below the surface. The excavation of this type of tunnel needs to consider many factors such as the thickness of the cover layer, geological conditions, environmental protection, and cost. Since this type of tunnel project will pass through a thick gravel layer, the traditional open-cut excavation of the cover layer is likely to cause large-scale surface damage, resulting in serious impact on the ecological environment. There are also slope stability problems, which increases the project cost and construction difficulty. Therefore, in order to alleviate the above problems, the project tends to reduce large-scale surface excavation and limit the large-section cavern excavation process to the cover layer, that is, to form a tunnel under the thick cover layer, thereby avoiding the adverse effects of large-scale surface excavation, such as environmental damage, slope stability problems, and increased capital investment.

[0022] However, after in-depth research, the applicant found that the special properties of the gravel stratum posed a great challenge to the stability of tunnel excavation. Specifically, the gravel stratum is significantly affected by groundwater. The presence of groundwater will weaken the adhesion between the gravel particles, resulting in reduced stratum strength, and it is very easy to cause instability such as landslides and roof collapse on the excavation surface, which seriously affects the safety of construction and the progress of the project. This instability not only increases the construction risk, but also makes the support and reinforcement of the tunnel more difficult, resulting in a significant increase in construction costs.

[0023] In the prior art, although there are some methods that attempt to solve the stability problem in the excavation of gravel strata, such as using means such as pumping groundwater, these methods often have many shortcomings in practical applications. For example, measures to pump groundwater may affect the balance of the surrounding water system, and it is difficult to completely control the water level in the gravel layer. Therefore, the defect of the prior art is that there is no efficient solution that takes into account environmental protection, economy and construction feasibility for the excavation stability problem of deep gravel tunnels.

[0024] In summary, the existing technology cannot meet the requirements for safe and stable construction of large-section tunnels under thick gravel overburden. Therefore, how to effectively improve the stability of the tunnel excavation surface in gravel strata and reduce the occurrence of landslides and roof falls has become a technical problem that needs to be solved urgently.

[0025] Based on this, the present application provides a large-section tunnel support structure and excavation method in a thick gravel overburden layer.

[0026] See also Figure 1~Figure 2 A large-section tunnel support structure with a thick gravel overburden layer includes a mountain advance reinforcement module 100 and an indoor support module 300, wherein the mountain advance reinforcement module 100 includes a high-pressure jet reinforcement body 110 and a grouting reinforcement body 120, the high-pressure jet reinforcement body 110 is vertically arranged outside the two side lines of the large-section cavern 200, and the grouting reinforcement body 120 is vertically evenly distributed in multiple lines in the excavation area of ​​the large-section cavern 200.

[0027] At the same time, the indoor support module 300 includes a top arch through anchor cable 400, a side wall through anchor cable 500 and an advance support body 600, wherein a plurality of top arch through anchor cables 400 are vertically arranged above the large-section cavern 200, and the lower end of the top arch through anchor cables 400 is located at the top arch portion of the large-section cavern 200. Further, a plurality of side wall through anchor cables 500 are horizontally arranged outside the side lines of the large-section cavern 200, and one end of the side wall through anchor cables 500 is located at the side line portion of the large-section cavern 200; the advance support body 600 is arranged at the top arch portion of the large-section cavern 200 along the excavation direction of the large-section cavern 200, so as to reinforce the top arch portion of the large-section cavern 200 in advance before the large-section cavern 200 is excavated.

[0028] On this basis, the setting of the mountain advance reinforcement module 100, through the combination of high-pressure jet reinforcement body 110 and grouting reinforcement body 120, can reinforce the surrounding strata in advance before tunnel excavation. The high-pressure jet reinforcement body 110 is vertically arranged outside the two side lines of the large-section cavern 200, which can strengthen the strata before excavation and prevent the collapse and displacement of large-area strata, thereby effectively improving the safety during tunnel excavation. The uniform arrangement of the grouting reinforcement body 120 in the excavation area further enhances the stability of the strata, reduces the softening of the soil caused by the influence of groundwater, and ensures that the strata do not suffer large-scale damage during tunnel excavation.

[0029] Secondly, the indoor support module 300 further strengthens the support effect in the tunnel through the reasonable layout of the top arch through anchor cable 400, the side wall through anchor cable 500 and the advance support body 600. The top arch through anchor cable 400 is set at the top arch of the tunnel. Multiple vertically arranged anchor cables can not only improve the bearing capacity of the top arch, but also effectively share and transmit the pressure from the excavation surface and the surrounding soil, avoiding the roof collapse caused by insufficient support. The side wall through anchor cables 500 are arranged horizontally on both sides of the tunnel. One end of the multiple anchor cables is set at the edge of the large-section cavern 200, which can stabilize the side wall structure of the tunnel and prevent the instability of the slope and landslide caused by the change of the excavation surface. In particular, the side wall anchor cables form an effective pulling effect through the through arrangement, further enhancing the stability of the side walls on both sides of the tunnel, improving the mutual restraint between the tunnel excavation surface and the surrounding soil, and avoiding the cracking or damage of the side wall caused by the looseness of the local stratum or the influence of groundwater.

[0030] Finally, the advance support body 600 is arranged in the tunnel arch along the tunnel excavation direction, which plays a role in advance reinforcement. By reinforcing the arch in advance, the advance support body 600 can effectively slow down or prevent the instability of the stratum below the excavation surface, share the pressure of the arch in advance, and ensure that the tunnel is not affected by excessive uneven stratum deformation during the excavation process, which significantly improves the construction safety and stability of the tunnel. Especially in deep gravel strata, the flow of groundwater and loose strata often pose a threat to tunnel stability. The design of the advance support body 600 can pre-enhance the support force of the arch before excavation, avoiding accidents such as arch collapse caused by uneven excavation progress.

[0031] Exemplarily, the high-pressure jet reinforcement body 110 is set at 1.5m outside the excavation side lines of the large-section cavern 200. The wall thickness of the high-pressure jet reinforcement body 110 is 1.2m to 1.5m. It is reinforced by high-pressure jet grouting. The hole spacing between adjacent high-pressure jet reinforcement bodies 110 is 0.8m to 1.2m, forming high-pressure jet reinforcement walls on both sides of the large-section cavern 200. Further, the bottom of the high-pressure jet reinforcement body 110 extends 3m to 5m below the excavation bottom plate of the large-section cavern 200, and the top of the high-pressure jet reinforcement body 110 is higher than the top arch elevation of the large-section cavern 200 by a distance greater than or equal to the cave height distance of the large-section cavern 200. Here, the cave height distance refers to the height of the large-section cavern 200. In this way, it can be ensured that the reinforcement body provides a stronger support for the upper stratum before excavation, preventing the top arch collapse or roof collapse during excavation. At the same time, the reinforcement depth of the tunnel bottom is effectively enhanced, further improving the stability of the bottom strata and preventing the bottom from sinking or becoming unstable due to groundwater or soil unevenness, thereby ensuring the safety and stability during tunnel construction.

[0032] Furthermore, due to the restrictions of terrain and structural layout, a first anchoring cavern 700 is formed on the upper part of the excavated large-section cavern 200 (that is, directly above the high-pressure jet reinforcement body 110). Multiple groups of first anchoring caverns 700 are evenly distributed above the large-section cavern 200, and one group of first anchoring caverns 700 corresponds to a high-pressure jet reinforcement body 110; the first anchoring cavern 700 is used as a construction working surface, and a hole is drilled downward to form a wall by high-pressure jetting. For example, the excavation section of the first anchoring cavern 700 is 5×5.5m (width×height), and its shape is a city gate cave type. After the excavation is completed, the first anchoring cavern 700 is synchronously supported.

[0033] After such arrangement, the arrangement of the first anchoring cavern 700 improves the effect of advance reinforcement of the upper strata in the early stage of tunnel excavation. By cooperating with the high-pressure jetting reinforcement body 110, the upper strata can be pre-treated before excavation, reducing the risk of collapse or roof collapse caused by groundwater and stratum heterogeneity. In particular, the high-pressure jetting reinforcement body 110 is arranged in the first anchoring cavern 700 at one end away from the large-section cavern 200. This design ensures that the reinforcement body can effectively penetrate into the covering layer before tunnel excavation, providing a more uniform and powerful reinforcement effect, so that the supporting force of the upper strata during tunnel excavation can be enhanced in advance, avoiding instability during excavation. This technical solution not only improves tunnel safety, but also further reduces construction risks and maintenance costs, ensuring the smooth progress of the project.

[0034] In some embodiments, Figure 1 , Figure 2 As shown, a connecting cavern 800 is provided between adjacent first anchoring caverns 700, and the end of the grouting reinforcement body 120 away from the large-section cavern 200 is located in the connecting cavern 800, and the top end of the arch through-anchor cable 400 is also located in the connecting cavern 800. Exemplarily, the grouting reinforcement body 120 is arranged in the excavation area of ​​the large-section cavern 200, and is reinforced by injecting cement grout after drilling. Furthermore, vertical drilling and grouting are performed downward in the connecting cavern 800 to reinforce the soil of the large-section cavern 200 to be excavated.

[0035] In this way, the setting of the connecting cavern 800 enables the grouting reinforcement body 120 to be evenly distributed in a larger range, providing a more comprehensive reinforcement effect on the stratum in the tunnel excavation area, and avoiding the problem of stratum instability caused by insufficient local reinforcement. In addition, the top of the arch through-anchor cable 400 is located in the connecting cavern 800, which can further strengthen the support strength of the arch part, improve the arch stability during the tunnel excavation process, and prevent the roof from being collapsed or other structural damage caused by uneven force during excavation. At the same time, the existence of the connecting cavern 800 also provides an installation space for the installation of the arch through-anchor cable 400, which is convenient for the arch through-anchor cable 400 to be constructed and laid downward from the connecting cavern 800. This design optimizes the integrity and effect of the support structure, and helps to improve the safety and construction progress of tunnel construction.

[0036] Exemplarily, the connection cavern 800 is arranged at a spacing of 20m, and the excavation section is 5×5.5m (width×height), and its shape is a gate hole type. After the excavation is completed, the connection cavern 800 is supported. Further, three rows of grouting holes are arranged at the bottom plate of the large-section cavern 200, with a spacing of 1.5m between the rows, and the two rows of holes on both sides are offset 5° outward. The distance at which the top of the grouting reinforcement body 120 is higher than the top arch elevation of the large-section cavern 200 is greater than or equal to the hole height distance of the large-section cavern 200, so that it can be ensured that the reinforcement body can provide sufficient support to the upper strata before excavation, enhance the stability of the top arch part, and prevent the top arch from collapsing or falling. And / or, the bottom end of the grouting reinforcement body 120 extends 1.5m~2.5m below the excavation bottom plate of the large-section cavern 200. This can effectively reinforce the bottom area of ​​the tunnel, enhance the overall stability of the bottom strata, and prevent the bottom from sinking or collapsing due to groundwater or loose soil. This design optimizes the overall reinforcement effect of the tunnel, improves the safety and stability during tunnel excavation, and reduces construction risks.

[0037] In some embodiments, in combination Figure 1 , Figure 2 A plurality of groups of second anchoring caverns 900 are provided on both sides of the large-section cavern 200, and one group of second anchoring caverns 900 corresponds to a side wall penetrating anchor cable 500, and one end of the side wall penetrating anchor cable 500 away from the large-section cavern 200 is located in the second anchoring cavern 900; further, adjacent second anchoring caverns 900 are staggered in the vertical direction; and / or, the vertical spacing between adjacent second anchoring caverns 900 is 6m to 8m.

[0038] In this way, by setting up multiple groups of second anchoring caverns 900 on both sides of the tunnel, and making each group of second anchoring caverns 900 correspond to a side wall through anchor cable 500, the stability of the tunnel side wall can be effectively enhanced. One end of the side wall through anchor cable 500 is set in the second anchoring cavern 900, which can provide stronger support for the side wall during the excavation process, and prevent structural damage such as side wall collapse or cracks due to excessive pressure on the side wall during excavation. In addition, the second anchoring caverns 900 are staggered in the vertical direction, and the vertical spacing between adjacent second anchoring caverns 900 is set to 6m to 8m. This design ensures that the reinforcement effect of the anchor cable on the tunnel side wall is uniform and continuous, effectively disperses the stress of the side wall, improves the overall stability of the tunnel side wall, and reduces the risk of instability caused by local stress concentration, thereby further ensuring the safety and construction progress during tunnel excavation.

[0039] For example, along the excavation direction of the large-section cavern 200, the horizontal spacing of adjacent sidewall through-anchor cables 500 is 4m, and the tension of the sidewall through-anchor cables 500 after installation is no more than 150t. In the vertical direction, the vertical distance between adjacent sidewall through-anchor cables 500 is no less than 10m, wherein the mountain thickness between the upper and lower second anchor caverns 900 and the large-section cavern 200 is no less than 30m, and the mountain thickness between the middle second anchor cavern 900 and the large-section cavern 200 is no less than 40m.

[0040] In some embodiments, Figure 1 , Figure 2 As shown, the advance support body 600 includes a support tube body 610 and a steel frame 620. There are multiple support tube bodies 610 evenly distributed along the top arch arc line of the large-section cavern 200, and the length direction of the support tube body 610 is consistent with the excavation direction of the large-section cavern 200; at the same time, the steel frame 620 is arranged on the periphery of the large-section cavern 200 along the outer peripheral contour of the large-section cavern 200, and along the excavation direction of the large-section cavern 200, a plurality of groups of steel frames 620 are arranged at intervals.

[0041] In this way, by designing the advance support body 600 as a combination of a support pipe body 610 and a steel frame 620, the structural stability during the tunnel excavation process is further enhanced. The support pipe body 610 is evenly distributed along the top arch arc of the large-section cavern 200 and is consistent with the tunnel excavation direction. This design enables the support pipe body 610 to effectively share the pressure of the top arch during the tunnel excavation process, enhance the support force of the top arch, and thus reduce the roof collapse or landslide caused by excessive top arch load. The steel frame 620 is arranged on the periphery of the large-section cavern 200, and a plurality of groups arranged at intervals are provided along the excavation direction, ensuring the continuity and uniformity of the external support structure of the tunnel, effectively restraining the deformation of the surrounding soil, and preventing the instability of the slope and surrounding strata. The design of this structure effectively improves the safety and stability during the tunnel excavation process by providing all-round advance reinforcement and support, and ensures the smooth progress of the construction progress.

[0042] In some embodiments, in combination Figure 2~Figure 4 The support tube body 610 includes a hollow outer tube 6110, an extruded inner column 6120, an axial stopper 6130 and a radial stopper 6140; wherein a slot 6111 is axially provided inside the hollow outer tube 6110 for inserting the extruded inner column 6120, and the two ends of the slot 6111 are an open end and a sealed end respectively. At the same time, the axial limit member 6130 can be movably arranged at the sealing end of the support tube body 610 close to the slot 6111, and the moving direction of the axial limit member 6130 is perpendicular to the length direction of the support tube body 610. In the process of the extrusion inner column 6120 moving along the length direction of the slot 6111, the axial limit member 6130 can be moved out of the hollow outer tube 6110 under the extrusion action of the extrusion inner column 6120 and extend into the mountain soil layer outside the hollow outer tube 6110.

[0043] Furthermore, the radial limit member 6140 can be movably disposed in the axial limit member 6130, and the moving direction of the radial limit member 6140 is parallel to the length direction of the support tube body 610. After the axial limit member 6130 is moved into place, when the extrusion inner column 6120 continues to move in the slot 6111, the radial limit member 6140 can be moved out of the axial limit member 6130 and extend into the mountain soil layer outside the axial limit member 6130 under the extrusion action of the extrusion inner column 6120.

[0044] On this basis, after the hollow outer tube 6110 is installed in place, the extruded inner column 6120 is gradually inserted along the length direction of the slot 6111 until the extruded inner column 6120 is close to the axial limit piece 6130. As the extruded inner column 6120 continues to move, the axial limit piece 6130 can be moved out of the hollow outer tube 6110 under the extrusion of the extruded inner column 6120 and extend into the mountain soil layer outside the hollow outer tube 6110, so that the displacement of the installed hollow outer tube 6110 in its own axial direction is limited; at the same time, the extruded inner column 6120 is continuously inserted along the length direction of the slot 6111. At this time, the radial limit piece 6140 is moved out of the axial limit piece 6130 under the extrusion of the extruded inner column 6120 and extends into the mountain soil layer outside the axial limit piece 6130, so that the displacement of the installed hollow outer tube 6110 in its own radial direction is limited. After such configuration, it is only necessary to insert and extrude the inner column 6120 along the length direction of the slot 6111 to successively remove the axial limiter 6130 and the radial limiter 6140, and limit the displacement of the hollow outer tube 6110 in its own axial and radial directions, thereby improving the installation stability of the support tube body 610.

[0045] In some embodiments, reference Figure 3 , Figure 5 The axial limiting member 6130 includes a first limiting portion 6131 and a first spring 6132. A movable cavity 6112 vertically connected to the slot 6111 is provided on the side wall of the hollow outer tube 6110. The first limiting portion 6131 is slidably arranged in the movable cavity 6112. The inner side wall of the movable cavity 6112 is connected to a side groove 6113. A support block extending into the side groove 6113 is provided on the first limiting portion 6131. ​​One end of the first spring 6132 is connected to the inner end wall of the side groove 6113, and the other end is connected to the support block.

[0046] At the same time, the first limiting portion 6131 includes a tip section 61311, a straight section 61312 and an inclined section 61313 which are axially connected in sequence. When the first spring 6132 is in a natural state, the tip section 61311 is located in the moving cavity 6112, and the inclined section 61313 extends into the slot 6111. Exemplarily, the tip section 61311 is sharpened at one end away from the straight section 61312, so that it can be easily inserted into the soil layer of the mountain.

[0047] Furthermore, the end of the inclined section 61313 facing the slot 6111 has a first abutting slope 61314, and the front end of the extruded inner column 6120 has a second abutting slope 6121 opposite to the first abutting slope 61314. When the extruded inner column 6120 is moved along the slot 6111, the second abutting slope 6121 can slide and abut with the first abutting slope 61314, so that the inclined section 61313 is pushed from the slot 6111 into the moving cavity 6112 under the extrusion action, and the tip section 61311 is extended out of the moving cavity 6112 and inserted into the soil layer of the mountain. Exemplarily, the front end of the extruded inner column 6120 refers to the front end of the extruded inner column 6120 along the moving direction.

[0048] On this basis, when the extruded inner column 6120 is moved along the length direction of the slot 6111, the second abutting slope 6121 will gradually approach the first abutting slope 61314 until it fits with the first abutting slope 61314. As the extruded inner column 6120 continues to move, the second abutting slope 6121 will push the first abutting slope 61314 to move from the slot 6111 to the moving cavity 6112, so that the inclined section 61313 also moves from the slot 6111 to the moving cavity 6112. At this time, the entire first limiting portion 6131 will move in the moving cavity 6112 in a direction away from the slot 6111, thereby allowing the tip section 61311 to move out of the opening at one end of the moving cavity 6112 away from the slot 6111 and insert into the soil layer of the mountain. At this time, the tip section 61311 can greatly limit the displacement of the hollow outer tube 6110 in its own axial direction.

[0049] In some embodiments, reference Figure 4 , Figure 6 The radial limiting member 6140 includes an abutting rod 6141, a connecting rod 6142, a plugging rod 6143 and a second spring 6144. The straight section 61312 is provided with an abutting channel 6131a, a connecting channel 6131b and a plugging channel 6131c which are connected in sequence. The length direction of the connecting channel 6131b is consistent with the moving direction of the axial limiting member 6130. The abutting channel 6131a is vertically connected to the side of the connecting channel 6131b close to the tip section 61311. The connecting channel 6131c is vertically connected to the side of the connecting channel 6131b close to the inclined section 61313, and the abutting channel 6131a is extended opposite to the connecting channel 6131b; the connecting rod 6142 is movably arranged in the connecting channel 6131b, the abutting rod 6141 is vertically connected to one end of the connecting rod 6142 and is slidably arranged in the abutting channel 6131a, and the plugging rod 6143 is vertically connected to the other end of the connecting rod 6142 and is slidably arranged in the plugging channel 6131c. Exemplarily, the length direction of the connecting rod 6142 is consistent with the length direction of the connecting channel 6131b, but the moving direction of the connecting rod 6142 is the width direction of the connecting channel.

[0050] At the same time, the second spring 6144 is arranged in the connecting channel 6131b, and along the length direction of the slot 6111, the second spring 6144 always has a tendency to push the connecting rod 6142 away from the abutting channel 6131a, so that when the second spring 6144 is in a natural state, the abutting rod 6141 is received in the abutting channel 6131a. Exemplarily, a groove is provided on the inner side wall of the connecting channel 6131b, one end of the second spring 6144 is connected to the inner end wall of the groove, and the other end is connected to the center of the connecting rod 6142, and the groove can accommodate the second spring 6144 in a compressed state, so that the existence of the second spring 6144 will not affect the movement of the connecting rod 6142 in the width direction of the connecting channel 6131b. Exemplarily, in order to improve the radial limiting effect, the abutment channel 6131a can be opened on the tip section 61311, so that there is a larger distance between the position where the abutment rod 6141 extends and the hollow outer tube 6110, and the radial limiting effect is better.

[0051] Further, combined with Figure 5 , Figure 6 The hollow outer tube 6110 is also provided with a branch groove 6114 parallel to the slot 6111, and a branch rod 6122 is provided parallel to one side of the extruded inner column 6120, and the branch rod 6122 is slidably inserted in the branch groove 6114. Exemplarily, the rear end of the branch rod 6122 is connected to the extruded inner column 6120 through a short rod. Among them, when the second abutment slope 6121 moves along the slot 6111 and completely passes through the end opening of the movable cavity 6112, the end opening of the plug-in channel 6131c is opposite to the end opening of the branch groove 6114 in the axial direction of the support tube body 610, and the abutment channel 6131a moves from the movable cavity 6112 to the outside, and the end of the branch rod 6122 is also opposite to the end of the plug-in rod 6143, so that when the extruded inner column 6120 continues to move along the slot 6111, the branch rod 6122 pushes part of the plug-in rod 6143 into the connecting channel 6131b, and at the same time drives the abutment rod 6141 to extend from the end opening of the abutment channel 6131a and insert into the mountain soil layer.

[0052] On this basis, when the extruded inner column 6120 moves in the slot 6111 and has pushed the inclined section 61313 from the slot 6111 into the movable cavity 6112, under the dual effects of the restriction of the side wall of the extruded inner column 6120 and the elastic force of the first spring 6132, the first limiting portion 6131 will remain in the current position and will no longer change. At the same time, in this position, the abutment channel 6131a also moves from the movable cavity 6112 to the mountain soil layer, and the end opening of the insertion channel 6131c is opposite to the end opening of the branch groove 6114 in the axial direction of the support tube body 610. In this case, the inner column 6120 is continuously moved and squeezed along the length direction of the slot 6111, and the end of the branch rod 6122 enters the insertion channel 6131c from the branch slot 6114, so that the end of the branch rod 6122 pushes the insertion rod 6143 part in the insertion channel 6131c to move from the insertion channel 6131c into the connection channel 6131b, and the connection rod 6142 is also pushed along the width direction of the moving channel, so that the second spring 6144 is compressed and enters the slot body, and then the abutment rod 6141 is also pushed and gradually moves out of the abutment channel 6131a in the abutment channel 6131a and is inserted into the mountain soil layer. Exemplarily, the moving front end of the abutment rod 6141 is also set as a tip, so that it can be inserted into the mountain soil layer more smoothly.

[0053] Exemplary, combined Figure 3 , Figure 5 The length of the branch rod 6122 is less than the length of the extrusion inner column 6120, and when the second abutting inclined surface 6121 of the extrusion inner column 6120 is slidably matched with the first abutting inclined surface 61314, the end of the branch rod 6122 is still a distance away from the lower end opening of the insertion channel 6131c. At the same time, when the second abutting inclined surface 6121 moves along the slot 6111 and completely passes through the end opening of the moving cavity 6112, the end of the branch rod 6122 is directly opposite to the lower end opening of the insertion channel 6131c, and the end of the branch rod 6122 abuts against the end of the insertion rod 6143.

[0054] In this case, the present application has an excellent effect, that is: the construction personnel only need to move the extruded inner column 6120 along the length direction of the slot 6111 to push the axial limiter 6130 and the radial limiter 6140 in sequence, that is, the first limiter 6131 is first radially moved out from the hollow outer tube 6110, and then the abutment rod 6141 is axially moved out from the first limiter 6131. ​​The reference object selected for the radial and axial directions here is the slot 6111. Therefore, it is only necessary to move the extruded inner column 6120 along the length direction of the slot 6111 to sequentially remove the two components, which is not only convenient to operate, but also more stable for the installation of the support tube body 610. Finally, concrete can be poured into the slot 6111 to fix the extruded inner column 6120 in the slot 6111.

[0055] Please refer to Figure 1~Figure 2 In the second aspect, the present application also provides a method for excavating a large-section tunnel in a thick gravel overburden layer. The large-section tunnel support structure in a thick gravel overburden layer based on the above scheme is implemented, comprising the following steps: The excavation surface of the large-section cavern 200 is divided into four modules, namely, the top arch module, the middle layer module, the lower layer module and the bottom plate protection layer module, wherein the top arch module is divided into five areas for construction, namely, I-1 layer, I-2 layer, I-3 layer, I-4 layer and I-5 layer; the middle layer module is divided into three areas for construction, namely, II-1 layer, II-2 layer and II-3 layer; the lower layer module is divided into three areas for construction, namely, III-1 layer, III-2 layer and III-3 layer; the bottom plate protection layer module is constructed last without partitioning; First, the first anchor cavern 700 and the second anchor cavern 900 are excavated and supported at the same time; High-pressure grouting reinforcement is adopted, and high-pressure grouting is vertically sprayed downward from the first anchor cavern 700 to the top arch side of the large-section cavern 200 to form a high-pressure grouting reinforcement body 110; After drilling, cement grout is injected for reinforcement. After drilling horizontally from the second anchor cavern 900 toward the edge of the large-section cavern 200, cement grout is injected to form a grouting reinforcement body 120. Installation and construction of advance support is carried out along the outer peripheral contour of the large-section cavern 200; Excavate the top arch module, the excavation sequence is: excavation and support of layer I-1, excavation and support of layer I-2, construction of 500 anchor cables for the side wall near the top layer of the large-section cavern 200, excavation and support of layer I-3, excavation and support of layer I-4, excavation and support of layer I-5, construction of 400 anchor cables for the top arch; Excavate the middle layer module, the excavation sequence is: excavation and support of layer II-1, excavation and support of layer II-2, construction of 500 anchor cables for the side wall near the middle layer of the large-section cavern 200, excavation and support of layer II-3; The lower layer modules are excavated in the following order: excavation and support of layer III-1, excavation and support of layer III-2, construction of anchor cables 500 for the side walls near the middle and lower layers of the large-section cavern 200, and excavation and support of layer III-3; Finally, the bottom plate protective layer module is excavated and supported as a whole.

[0056] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A large-section tunnel support structure with thick gravel overburden, characterized in that: include: A mountain advance reinforcement module (100) comprises a high pressure jet reinforcement body (110) and a grouting reinforcement body (120), wherein the high pressure jet reinforcement body (110) is vertically arranged outside the side lines of both sides of a large-section cavern (200), and a plurality of grouting reinforcement bodies (120) are vertically evenly distributed in the excavation area of ​​the large-section cavern (200); The indoor support module (300) comprises a top arch through-penetrating anchor cable (400), a side wall through-penetrating anchor cable (500) and an advanced support body (600), wherein: A plurality of the top arch through-penetrating anchor cables (400) are vertically arranged above the large-section cavern (200), and the lower ends of the top arch through-penetrating anchor cables (400) are located at the top arch portion of the large-section cavern (200); A plurality of the side wall penetration anchor cables (500) are horizontally arranged outside the side lines of both sides of the large cross-section cavern (200), and one end of the side wall penetration anchor cable (500) is located at the side line of the large cross-section cavern (200); The advance support body (600) is arranged at the top arch portion of the large-section cavern (200) along the excavation direction of the large-section cavern (200) and is used to reinforce the top arch portion of the large-section cavern (200) in advance before the large-section cavern (200) is excavated.

2. A large-section tunnel support structure with thick gravel overburden according to claim 1, characterized in that: A plurality of groups of first anchoring caverns (700) are evenly distributed horizontally above the large-section cavern (200), and one group of the first anchoring caverns (700) corresponds to one of the high-pressure jet reinforcement bodies (110); One end of the high-pressure injection reinforcement body (110) away from the large-section cavern (200) is located in the first anchoring cavern (700).

3. A large-section tunnel support structure with thick gravel overburden according to claim 2, characterized in that: The distance that the top of the high-pressure spray reinforcement body (110) is higher than the top arch elevation of the large-section cavern (200) is greater than or equal to the cave height distance of the large-section cavern (200); And / or, the bottom end of the high-pressure spray reinforcement body (110) extends 3m to 5m below the excavation bottom plate of the large-section cavern (200).

4. A large-section tunnel support structure with thick gravel overburden according to claim 2, characterized in that: A connecting cavern (800) is provided between adjacent first anchoring caverns (700), one end of the grouting reinforcement body (120) away from the large-section cavern (200) is located in the connecting cavern (800), and the top end of the arch-penetrating anchor cable (400) is also located in the connecting cavern (800).

5. A large-section tunnel support structure with thick gravel overburden according to claim 4, characterized in that: The distance that the top of the grouting reinforcement body (120) is higher than the top arch elevation of the large-section cavern (200) is greater than or equal to the cave height distance of the large-section cavern (200); And / or, the bottom end of the grouting reinforcement body (120) extends 1.5m to 2.5m below the excavation bottom plate of the large-section cavern (200).

6. A large-section tunnel support structure with thick gravel overburden according to claim 2, characterized in that: A plurality of groups of second anchoring caverns (900) are provided on both sides of the large-section cavern (200), one group of the second anchoring caverns (900) corresponds to one of the side wall penetrating anchor cables (500), and one end of the side wall penetrating anchor cable (500) away from the large-section cavern (200) is located in the second anchoring cavern (900); In the vertical direction, adjacent second anchoring caverns (900) are staggered; and / or, the vertical spacing between adjacent second anchoring caverns (900) is 6m to 8m.

7. A large-section tunnel support structure with thick gravel overburden according to any one of claims 1 to 6, characterized in that: The advanced support body (600) comprises a support pipe body (610) and a steel frame (620); a plurality of support pipe bodies (610) are evenly distributed along the top arch arc of the large-section cavern (200); and the length direction of the support pipe body (610) is consistent with the excavation direction of the large-section cavern (200); The steel frames (620) are arranged on the periphery of the large-section cavern (200) along the outer peripheral contour of the large-section cavern (200), and a plurality of groups of the steel frames (620) are arranged at intervals along the excavation direction of the large-section cavern (200).

8. A large-section tunnel support structure with thick gravel overburden according to claim 7, characterized in that: The support tube body (610) comprises a hollow outer tube (6110), an extruded inner column (6120), an axial stopper (6130) and a radial stopper (6140); wherein: A slot (6111) is axially provided inside the hollow outer tube (6110) for the extruded inner column (6120) to be inserted into, and the two ends of the slot (6111) are respectively an open end and a sealed end; The axial limiter (6130) is movably arranged at the sealing end of the support tube body (610) close to the slot (6111), and the moving direction of the axial limiter (6130) is perpendicular to the length direction of the support tube body (610). When the extrusion inner column (6120) moves along the length direction of the slot (6111), the axial limiter (6130) can be moved out of the hollow outer tube (6110) and extend into the mountain soil layer outside the hollow outer tube (6110) under the extrusion action of the extrusion inner column (6120); The radial limit member (6140) can be movably arranged in the axial limit member (6130), and the moving direction of the radial limit member (6140) is parallel to the length direction of the support tube body (610). After the axial limit member (6130) moves into place, the extrusion inner column (6120) continues to move in the slot (6111). Under the extrusion action of the extrusion inner column (6120), the radial limit member (6140) can move out of the axial limit member (6130) and extend into the mountain soil layer outside the axial limit member (6130).

9. A large-section tunnel support structure with thick gravel overburden according to claim 8, characterized in that: The axial limiting member (6130) comprises a first limiting portion (6131) and a first spring (6132). A movable cavity (6112) vertically connected to the slot (6111) is provided on the side wall of the hollow outer tube (6110). The first limiting portion (6131) is slidably arranged in the movable cavity (6112). The inner side wall of the movable cavity (6112) is connected to a side groove (6113). The first limiting portion (6131) is provided with a support block extending into the side groove (6113). One end of the first spring (6132) is connected to the inner end wall of the side groove (6113), and the other end is connected to the support block. The first limiting portion (6131) comprises a tip section (61311), a straight section (61312) and an inclined section (61313) which are axially connected in sequence. When the first spring (6132) is in a natural state, When the extrusion inner column (6120) is moved along the slot (6111), the tip section (61311) is located in the movable cavity (6112), and the inclined section (61313) extends into the slot (6111); the end of the inclined section (61313) facing the slot (6111) has a first abutting slope (61314), and the front end of the extrusion inner column (6120) has a second abutting slope (6121) opposite to the first abutting slope (61314); when the extrusion inner column (6120) is moved along the slot (6111), the second abutting slope (6121) can be slidably abutted with the first abutting slope (61314), so that the inclined section (61313) is pushed from the slot (6111) into the movable cavity (6112) under the extrusion action, and at the same time, the tip section (61311) extends out of the movable cavity (6112) and is inserted into the soil layer of the mountain; The radial limiting member (6140) comprises an abutting rod (6141), a connecting rod (6142), a plugging rod (6143) and a second spring (6144); the straight section (61312) is provided with an abutting channel (6131a), a connecting channel (6131b) and a plugging channel (6131c) which are connected in sequence; the length direction of the connecting channel (6131b) is consistent with the moving direction of the axial limiting member (6130); a) is vertically connected to a side of the connecting channel (6131b) close to the tip section (61311), the insertion channel (6131c) is vertically connected to a side of the connecting channel (6131b) close to the inclined section (61313), and the abutment channel (6131a) is arranged to extend in opposite directions from the connecting channel (6131b), the connecting rod (6142) is movably arranged in the connecting channel (6131b), and the abutment rod (6141) is vertically connected to One end of the connecting rod (6142) is slidably disposed in the abutment channel (6131a), and the plug-in rod (6143) is vertically connected to the other end of the connecting rod (6142) and slidably disposed in the plug-in channel (6131c); the second spring (6144) is disposed in the connecting channel (6131b), and along the length direction of the slot (6111), the second spring (6144) always has the function of pulling the connecting rod (6142) away from the abutment channel. The abutment rod (6141) is received in the abutment channel (6131a) in a tendency to push the second spring (6144) sideways so that when the second spring (6144) is in a natural state; a branch groove (6114) parallel to the slot (6111) is further provided in the hollow outer tube (6110); a branch rod (6122) is provided parallel to one side of the extruded inner column (6120); the branch rod (6122) is slidably inserted in the branch groove (6114), wherein: When the second abutment slope (6121) moves along the slot (6111) and completely passes through the end opening of the movable cavity (6112), the end opening of the plug-in channel (6131c) and the end opening of the branch groove (6114) are opposite to each other in the axial direction of the support tube body (610), and the abutment channel (6131a) moves from the movable cavity (6112) to the outside, and the end of the branch rod (6122) and the end of the plug-in rod (6143) are also opposite to each other and fit together, so that when the extruded inner column (6120) continues to move along the slot (6111), the branch rod (6122) pushes part of the plug-in rod (6143) into the connecting channel (6131b), and at the same time drives the abutment rod (6141) to extend from the end opening of the abutment channel (6131a) and insert into the mountain soil layer.

10. A method for excavating a large-section tunnel in a thick gravel overburden layer, which is realized based on the large-section tunnel support structure in a thick gravel overburden layer according to any one of claims 6 to 9, characterized in that: The following steps are involved: The excavation surface of the large-section cavern (200) is divided into four modules, namely, a top arch module, a middle layer module, a lower layer module, and a bottom plate protection layer module, wherein the top arch module is divided into five areas for construction, namely, I-1 layer, I-2 layer, I-3 layer, I-4 layer, and I-5 layer; the middle layer module is divided into three areas for construction, namely, II-1 layer, II-2 layer, and II-3 layer; the lower layer module is divided into three areas for construction, namely, III-1 layer, III-2 layer, and III-3 layer; the bottom plate protection layer module is constructed last without partitioning; First, the first anchor cavern (700) and the second anchor cavern (900) are excavated and supported at the same time; High-pressure grouting reinforcement is adopted to form the high-pressure grouting reinforcement body (110) by vertically grouting from the first anchoring cavern (700) downward toward the top arch side of the large-section cavern (200); Adopting the method of reinforcing by injecting cement grout after drilling, drilling horizontally from the second anchoring cavern (900) toward the edge of the large-section cavern (200) and injecting cement grout to form the grouting reinforcement body (120); Performing installation construction of advance support along the outer peripheral contour of the large-section cavern (200); Excavating the top arch module, the excavation sequence is: excavation and support of layer I-1, excavation and support of layer I-2, construction of side wall cross-through anchor cables (500) near the top layer of the large-section cavern (200), excavation and support of layer I-3, excavation and support of layer I-4, excavation and support of layer I-5, and construction of top arch cross-through anchor cables (400); Excavating the middle layer module, the excavation sequence is: excavation and support of layer II-1, excavation and support of layer II-2, construction of anchor cables (500) for the side wall near the middle layer of the large-section cavern (200), and excavation and support of layer II-3; Excavating the lower layer module, the excavation sequence is: excavation and support of layer III-1, excavation and support of layer III-2, construction of side wall through-anchor cable (500) near the middle and lower layer of the large-section cavern (200), and excavation and support of layer III-3; Finally, the bottom plate protective layer module is excavated and supported as a whole.

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