A graded energy dissipation and excavation structure for tunnels crossing creep fault zones

Abstract

The present invention discloses a graded energy dissipation and excavation structure for a tunnel crossing a creep fault zone, comprising a grouting reinforcement layer, an excavation support layer, an energy dissipation layer, and a tunnel support layer. The grouting reinforcement layer solidifies and reinforces the loose and broken rock mass in the creep fault zone into a whole through grouting reinforcement; the excavation support layer comprises a steel mesh, an NPR anchor cable, and foam concrete; the energy dissipation layer comprises a geotextile, a graded energy dissipation system, and a longitudinal energy dissipation joint, and the graded energy dissipation system comprises a primary energy dissipation unit, a secondary energy dissipation unit, and a tertiary energy dissipation unit; the tunnel support layer comprises a tunnel primary support, a tunnel waterproofing layer, and a tunnel secondary lining. The energy dissipation unit comprises a rear portion, a middle portion, and a front portion of the energy dissipation unit. The rear portion of the energy dissipation unit is made of porous rubber; the middle portion of the energy dissipation unit comprises a pressure relief chamber, a pressure relief liquid, and solid rubber; and the front portion of the energy dissipation unit comprises a pressure relief hole and a pressure relief valve.

Description

Technical Field

[0001] The present invention relates to a tunnel structure, in particular to a graded energy dissipation and excavation structure for a tunnel passing through a large creep fault zone, belonging to the technical field of underground engineering for tunnel construction. Background Art

[0002] In recent years, as my country's transportation infrastructure has entered a period of comprehensive development, an increasing number of transportation tunnels have traversed fault zones or large active fault zones, such as the Chengdu-Lanzhou Railway, the Lanzhou-Chongqing Railway, the Sichuan-Tibet Railway, and the Central Yunnan Water Diversion Project. Rock underground engineering is a key component of major projects in western China, with long tunnels serving as the controlling elements of highways, railways, and water diversion projects. These long tunnels in western China span diverse geomorphic and geological units and inevitably intersect multiple active fault zones.

[0003] The movement of active fault zones seriously endangers the construction and operation safety of tunnels. The movement modes of active fault zones are mainly divided into creep and stick-slip. Creep dislocation is the slow sliding process of the fracture area caused by the active fault zone over time. It is a slow form of movement with a time-accumulation effect; stick-slip dislocation is a rupture movement caused by rapid fracture during an earthquake. It is a sudden and violent form of movement. Among them, the impact of creep fault zones on tunnel structures is mainly manifested in the following: the cumulative displacement generated by the creep of active faults is restricted by the rigid support of the tunnel and continuously accumulates strain energy. When the amount of strain energy exceeds the limit that the tunnel support structure can bear, it will cause severe shear damage to the tunnel structure. At present, a considerable number of tunnels under construction or planned to be built pass through creep active fault zones, facing the problem of tunnel anti-creep dislocation.

[0004] Current fault-crossing tunnel mitigation measures employed in practical engineering projects both domestically and internationally can be broadly summarized as "overexcavation design," "articulated design," and "isolation and energy dissipation design," or a combination of these three. Currently, there is no specific design method for tunnel structures designed to resist creep dislocation when crossing creep fault zones. Therefore, a graded energy dissipation and excavation design is proposed for deep tunnels crossing creep fault zones and high-intensity earthquake zones. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings and deficiencies of the existing technical conditions and provide a graded energy dissipation and expansion structure for a tunnel crossing a creep fault zone.

[0006] The present invention adopts the following technical solutions:

[0007] A graded energy dissipation and excavation structure for tunnels crossing creep fault zones includes a grouting reinforcement layer, an excavation support layer, an energy dissipation layer, and a tunnel support layer. This structure is installed at the advance excavation site of the creep fault zone through which the tunnel is to pass. At the advance excavation site, the grouting reinforcement layer, the excavation support layer, the energy dissipation layer, and the tunnel support layer are constructed in order from the outermost layer to the innermost layer.

[0008] The grouting reinforcement layer solidifies and reinforces the loose and broken rock mass in the creep fault zone through small-duct grouting reinforcement to form a whole; the excavation support layer is used to reinforce and support the grouting reinforcement layer and the advance excavation of the tunnel; the energy dissipation layer is arranged between the excavation support layer and the tunnel support layer. The energy dissipation layer has both elastic and compressive properties and is used to dissipate energy in the creep fault zone; the tunnel support layer is arranged on the inner wall of the tunnel to support the graded energy dissipation excavation structure.

[0009] Furthermore, the thickness of the grouting reinforcement layer is one to two times the diameter of the creep fracture zone.

[0010] Furthermore, the excavation support layer includes a steel mesh, NPR anchor cables, and foam concrete. The steel mesh is secured to the grouting reinforcement layer via the NPR anchor cables; the foam concrete is applied beneath the NPR anchor cables and steel mesh. The steel mesh can be single-layered or double-layered, depending on the average annual activity rate of the creep fault zone.

[0011] Furthermore, the energy dissipation layer includes a geotextile, a graded energy dissipation system, and longitudinal energy dissipation joints. The geotextile is arranged on the outside of the foam concrete to prevent the foam concrete from falling debris; the graded energy dissipation system is arranged on the inside of the geotextile; and the longitudinal energy dissipation joints are located between adjacent graded energy dissipation systems.

[0012] Furthermore, a graded energy dissipation system is installed parallel to the tunnel surface in the advanced tunnel excavation section and the transition section between the tunnel and the normal tunnel section. The pores of each energy dissipation unit in the graded energy dissipation system are filled with rubber particles and fixed with an adhesive. The graded energy dissipation system is composed of multiple stages of energy dissipation units.

[0013] Furthermore, the energy dissipation unit is composed of a rear portion, a middle portion, and a front portion, which are an integral, demoldable structure made of high-strength rubber. The rear portion is made of porous rubber; the middle portion includes a pressure relief chamber, a pressure relief fluid, and solid rubber. The pressure relief fluid is placed in the pressure relief chamber, and the outside of the pressure relief chamber is wrapped with solid rubber. The front portion includes a pressure relief hole, the end of which is connected to the pressure relief hole, and a pressure relief valve is installed in the pressure relief hole.

[0014] Preferably, the diameters of the multi-stage energy dissipation units increase sequentially, the pressure thresholds of the pressure relief valves of the energy dissipation units decrease sequentially, and the capacity of the pressure relief chambers of the energy dissipation units increases sequentially.

[0015] Preferably, in the graded energy dissipation system, the energy dissipation units at each level are fixedly connected by an adhesive, and the gaps are filled with rubber particles and fixed by the adhesive; the adhesive has the same elasticity as solid rubber.

[0016] Preferably, the longitudinal energy dissipation seam timely and evenly distributes the total displacement of the creep fault zone to each graded energy dissipation system, and the graded energy dissipation system sequentially dissipates energy through energy dissipation units at each level according to the size of the displacement.

[0017] The method for tunnel excavation through creep fault zone by graded energy dissipation is implemented as follows:

[0018] S1. Determine the specific mileage of the creep fault zone through preliminary geological survey data combined with in-tunnel drilling and geophysical exploration methods; and determine the scale and annual average activity rate of the creep fault zone.

[0019] S2. Based on the specific mileage, scale, and annual average activity rate of the creep fault zone determined in step S1, advance tunnel excavation is performed to form a tunnel excavation section.

[0020] S3. A grouting reinforcement layer, an expansion support layer, an energy dissipation layer, and a tunnel support layer are sequentially applied to the tunnel expansion section to form a graded energy dissipation expansion structure in the creep fault zone.

[0021] The energy dissipation process of the graded energy dissipation and excavation structure is as follows: when creep dissipation occurs in the creep fault zone, the grouting reinforcement layer and the excavation support layer consume a certain amount of creep dissipation strain energy through extrusion deformation; when the creep dissipation strain energy exceeds the bearing capacity of the grouting reinforcement layer and the excavation support layer, the longitudinal energy dissipation joints of the energy dissipation layer evenly distribute the creep dissipation strain energy to each graded energy dissipation system; as the creep dissipation strain energy continues to accumulate, each energy dissipation unit dissipates the strain energy in turn by releasing pressure relief fluid.

[0022] When the dislocation value of the creep dislocation in the creep fault zone reaches the design value of the graded energy dissipation and excavation expansion structure, the pressure relief fluid in the graded energy dissipation system is completely discharged, and the accumulated creep dislocation strain energy is jointly borne by the solid rubber, porous rubber and tunnel support layer in the energy dissipation unit.

[0023] The beneficial effects of the present invention are:

[0024] (1) The present invention provides a targeted solution to the problem of anti-fracture when a tunnel passes through a creep fault zone. Through the energy dissipation effect of the graded energy dissipation and excavation structure, the tunnel can consume the strain energy accumulated by creep displacement in a timely manner, and can cope with large creep displacement accumulated over a long time span, thereby ensuring the integrity and safety of the tunnel support structure.

[0025] (2) The hierarchical energy dissipation and excavation structure of the present invention comprehensively utilizes the excavation design, energy dissipation design and articulated design, and can cope with creep fault zones of different scales and annual average activity rates.

[0026] (3) The hierarchical energy dissipation and excavation structure of the present invention realizes the timely dissipation of strain energy accumulated when the tunnel passes through the creep fault zone, thereby avoiding damage to the tunnel structure under the action of long-term stress. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 It is a three-view cross-section of the energy dissipation unit of the present invention.

[0029] Figure 2 It is a longitudinal section of the grouting reinforcement layer, the expansion support layer, and the energy dissipation layer of the present invention.

[0030] Figure 3 It is an overall longitudinal sectional view of the present invention.

[0031] Figure 4 It is an overall cross-sectional view of the present invention.

[0032] The diagram is for illustrative purposes only, as the spacing and dimensions between components are exaggerated to show their locations. The diagram includes: 1 porous rubber, 2 pressure relief cavity, 3 pressure relief fluid, 4 solid rubber, 5 pressure relief hole, 6 pressure relief valve, 7 rear portion of energy dissipation unit, 8 middle portion of energy dissipation unit, 9 front portion of energy dissipation unit, 10 energy dissipation unit, 11 grouting reinforcement layer, 12 NPR anchor cable, 13 steel mesh, 14 foam concrete, 15 geotextile, 16 primary energy dissipation unit, 17 secondary energy dissipation unit, 18 tertiary energy dissipation unit, 19 graded energy dissipation system, 20 longitudinal energy dissipation joint, 21 energy dissipation layer, 22 surrounding rock, 23 expanded excavation support layer, 24 primary tunnel support, 25 tunnel waterproofing layer, 26 secondary tunnel lining, 27 tunnel support layer, 28 creep fault zone. DETAILED DESCRIPTION

[0033] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0034] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0035] Example 1:

[0036] A graded energy dissipation and excavation structure for tunnels crossing creep fault zones includes a grouting reinforcement layer 11, an excavation support layer 23, an energy dissipation layer 21, and a tunnel support layer 27. This graded energy dissipation and excavation structure allows for advanced tunnel excavation based on the location, size, and annual average activity rate of the creep fault zone 28 through which the tunnel is intended to pass. At the advanced tunnel excavation site, the grouting reinforcement layer 11, the excavation support layer 23, the energy dissipation layer 21, and the tunnel support layer 27 are constructed in this order, from outer to inner layers.

[0037] The grouting reinforcement layer 11 solidifies and reinforces the loose and broken rock mass in the creep fault zone 28 into a whole through small-duct grouting reinforcement; the excavation support layer 23 is used to reinforce and support the grouting reinforcement layer 11 and the advance excavation of the tunnel; the energy dissipation layer 21 is arranged between the excavation support layer 23 and the tunnel support layer 27. The energy dissipation layer 21 has both elastic and compressive properties and is used to dissipate energy in the creep fault zone; the tunnel support layer 27 is arranged on the inner wall of the tunnel to fully support the graded energy dissipation excavation structure.

[0038] The thickness of the grouting reinforcement layer 11 is set to be one to two times the hole diameter according to the fracture condition of the creep fracture zone 28 .

[0039] The excavation support layer 23 includes a steel mesh 13, an NPR anchor cable 12 and foam concrete 14. The steel mesh 13 is fixed in the grouting reinforcement layer 11 by the NPR anchor cable 12; the diameter of the NPR anchor cable 12 increases when stretched, thereby enhancing the anchoring effect. The foam concrete 14 is laid under the NPR anchor cable 12 and the steel mesh 13. The inner surface of the foam concrete 14 is smoothed and flattened, and the laying thickness is determined according to the 28-year average activity rate of the creep fracture zone. The steel mesh 13 is selected to have a single-layer or double-layer structure according to the 28-year average activity rate of the creep fracture zone. The NPR anchor cable 12 is selected to have a suitable laying density according to the 28-year average activity rate of the creep fracture zone.

[0040] The energy dissipation layer 21 includes a geotextile 15, a graded energy dissipation system 19, and longitudinal energy dissipation joints 20. The geotextile 15 is placed outside the foam concrete 14 to prevent debris from falling. The graded energy dissipation system 19 is placed inside the geotextile 15, and the distribution intervals of the graded energy dissipation systems 19 are determined based on the size and annual average activity rate of the creep fault zone 28. The longitudinal energy dissipation joints 20 are distributed at intervals based on the size and annual average activity rate of the creep fault zone 28 and are located between adjacent graded energy dissipation systems 19.

[0041] A graded energy dissipation system 19 is set up in parallel with the tunnel surface at the tunnel advance excavation section formed by the tunnel advance excavation, and in the transition section between the tunnel and the normal section. The pores of the energy dissipation units of each level of the graded energy dissipation system 19 are filled with rubber particles and fixed by an adhesive. The graded energy dissipation system 19 is composed of a multi-level energy dissipation unit 10; when the number of energy dissipation units 10 is three, it includes a primary energy dissipation unit 16, a secondary energy dissipation unit 17 and a tertiary energy dissipation unit 18. The primary energy dissipation unit 16, the secondary energy dissipation unit 17 and the tertiary energy dissipation unit 18 are fixedly connected by an adhesive, the outermost layer is the tertiary energy dissipation unit 18, the middle layer is the secondary energy dissipation unit 17, and the innermost layer is the primary energy dissipation unit 16.

[0042] The tunnel support layer 27 includes the tunnel primary support 24, the tunnel waterproof layer 25 and the tunnel secondary lining 26, and is constructed according to conventional tunnel construction methods, that is, the tunnel support layer 27 is supported in sequence by the tunnel primary support 24, the tunnel waterproof layer 25 and the tunnel secondary lining 26.

[0043] The energy dissipation unit 10 is composed of a rear portion 7, a middle portion 8, and a front portion 9. The rear portion 7, the middle portion 8, and the front portion 9 are an integral demolding structure made of high-strength rubber. The rear portion 7 is made of porous rubber 1; the middle portion 8 includes a pressure relief chamber 2, a pressure relief fluid 3, and a solid rubber 4. The pressure relief fluid 3 is placed in the pressure relief chamber 2, and the outside of the pressure relief chamber 2 is wrapped by the solid rubber 4. The front portion 9 includes a pressure relief hole 5. The end of the pressure relief chamber 2 is connected to the pressure relief hole 5. A pressure relief valve 6 is provided in the pressure relief hole 5.

[0044] The application method of the present invention is as follows:

[0045] S1 determines the specific mileage of creep fault zone 28 through preliminary geological survey data combined with in-tunnel drilling and geophysical exploration methods; and determines the scale and annual average activity rate of creep fault zone 28.

[0046] S2 conducts advance excavation of the tunnel based on the specific mileage, scale and annual average activity rate of the creep fault zone 28 confirmed by S1, and forms a tunnel excavation section after the advance excavation of the tunnel.

[0047] S3: Grouting reinforcement layer 11, excavation support layer 23, energy dissipation layer 21 and tunnel support layer 27 are applied to the tunnel expansion section in sequence.

[0048] When creep dislocation occurs in the creep fault zone 28, the grouting reinforcement layer 11 and the expanded excavation support layer 23 first consume a certain amount of creep dislocation strain energy through extrusion deformation; when the creep dislocation strain energy exceeds the bearing limit of the grouting reinforcement layer 11 and the expanded excavation support layer 23, the longitudinal energy dissipation joint 20 of the energy dissipation layer 21 evenly distributes the creep dislocation strain energy to each graded energy dissipation system 19; as the creep dissipation strain energy continues to accumulate, the third-level energy dissipation unit 18, the second-level energy dissipation unit 17 and the first-level energy dissipation unit 16 consume the strain energy in turn by releasing the pressure relief fluid 3.

[0049] When the dislocation value of the creep fault zone 28 reaches the design value of the graded energy dissipation and excavation structure, the pressure relief fluid 3 of the graded energy dissipation system 19 is basically completely discharged, which meets the service life requirements of the project. The subsequent accumulated creep dislocation strain energy is jointly borne by the solid rubber 4, the porous rubber 1 and the tunnel support layer 27.

[0050] Preferably, the solid rubber 4 and the porous rubber 1 are made of the same material but different processes, and have good elasticity and compressibility. When the pressure relief liquid 3 in the pressure relief chamber 2 is squeezed and finally discharged through the pressure relief valve 6, the porous rubber is also compressed to density at the same time and has the same elasticity as the solid rubber, ensuring uniformity of force.

[0051] Preferably, the pressure relief chamber 2 is filled with the pressure relief liquid 3 without the presence of air. The pressure relief liquid 3 is cooled to the boiling point to remove the gas dissolved therein, and the pressure relief liquid 3 is incompressible.

[0052] Preferably, the pressure relief fluid 3 is a neutral medium, does not chemically react with rubber, does not cause steel bar corrosion, does not cause aging of concrete structures, has a low freezing point and a high boiling point, and does not solidify or evaporate under tunnel temperature conditions.

[0053] Preferably, an atomizing nozzle is provided on the pressure relief valve 6 to prevent the pressure relief fluid 3 from being sprayed out at high speed under high pressure and causing damage to the front structure.

[0054] Preferably, the pressure relief valve 6 can be set with a pressure threshold. When the pressure in the pressure relief chamber reaches the pressure threshold, the pressure relief valve 6 slowly sprays atomized pressure relief liquid at a certain frequency until the pressure in the pressure relief chamber is lower than the pressure threshold or the pressure relief liquid is completely discharged.

[0055] Preferably, the NPR anchor cable 12 passes through the grouting reinforcement layer 11, firmly fixes the steel mesh 13 on the surface of the grouting reinforcement layer 11, increases the strength of the grouting reinforcement layer 11 and prevents large pieces of the grouting reinforcement layer from falling off.

[0056] Preferably, the inner surface of the foam concrete 14 is flat and smooth, which plays a certain buffering role and prevents debris of the grouting reinforcement layer 11 from falling.

[0057] Preferably, the geotextile 15 is a multi-layer thick woven fabric with high tensile strength and small pores to prevent the debris from falling after the foam concrete is crushed.

[0058] Preferably, the thickness and structural form of the tunnel primary support layer 24, the tunnel waterproof layer 25, and the tunnel secondary lining 26 are determined according to the scale of the creep fault zone, the average annual activity rate, and the groundwater development conditions. As the scale of the creep fault zone 28 and the average annual activity rate increase, the contour of the tunnel transitions from a nearly elliptical contour to a circular contour.

[0059] From the above description, it can be seen that the above embodiments of the present application achieve the following technical effects:

[0060] (1) The present invention provides a targeted solution to the problem of anti-fracture when a tunnel passes through a creep fault zone. Through the energy dissipation effect of the graded energy dissipation and excavation structure, the tunnel can consume the strain energy accumulated by creep displacement in a timely manner, and can cope with large creep displacement accumulated over a long time span, thereby ensuring the integrity and safety of the tunnel support structure.

[0061] (2) The hierarchical energy dissipation and excavation structure of the present invention comprehensively utilizes the excavation design, energy dissipation design and articulated design, and can cope with creep fault zones of different scales and annual average activity rates.

[0062] (3) The hierarchical energy dissipation and excavation structure of the present invention realizes the timely dissipation of strain energy accumulated when the tunnel passes through the creep fault zone, thereby avoiding damage to the tunnel structure under the action of long-term stress.

Claims

1. A hierarchical energy dissipation and excavation structure for a tunnel crossing a creep fault zone, characterized by: It includes a grouting reinforcement layer, an expansion support layer, an energy dissipation layer and a tunnel support layer. The hierarchical energy dissipation expansion structure is set up at the creep fault zone where the tunnel is to pass through for advance tunnel excavation. The grouting reinforcement layer, the expansion support layer, the energy dissipation layer and the tunnel support layer are constructed in sequence from the outer layer to the inner layer. The grouting reinforcement layer consolidates and reinforces the loose and broken rock mass in the creep fault zone to form a whole; the excavation support layer is used to reinforce and support the grouting reinforcement layer and the advance excavation of the tunnel; the energy dissipation layer is arranged between the excavation support layer and the tunnel support layer, and the energy dissipation layer has both elastic and compressive properties to dissipate energy in the creep fault zone; the tunnel support layer is arranged on the inner wall of the tunnel to support the graded energy dissipation excavation structure; The excavation support layer includes a steel mesh, NPR anchor cables and foam concrete; the steel mesh is fixed in the grouting reinforcement layer by the NPR anchor cables; the foam concrete is laid under the NPR anchor cables and the steel mesh; The energy dissipation layer includes geotextile, graded energy dissipation system and longitudinal energy dissipation joint; the geotextile is arranged on the outside of the foam concrete; the graded energy dissipation system is arranged on the inside of the geotextile; the longitudinal energy dissipation joint is located between adjacent graded energy dissipation systems; The longitudinal energy dissipation seam distributes the total displacement of the creep fault zone to each graded energy dissipation system in a timely and uniform manner. The graded energy dissipation system dissipates energy in sequence through energy dissipation units at each level according to the displacement of the creep fault zone. A graded energy dissipation system is arranged in parallel with the tunnel surface at the tunnel advance excavation section formed by the tunnel advance excavation and in the transition section between the tunnel and the normal section; the pores of the energy dissipation units of each level of the graded energy dissipation system are filled with rubber particles and fixed by an adhesive; the graded energy dissipation system is composed of multiple levels of energy dissipation units.

2. The hierarchical energy dissipation and excavation structure for tunnels crossing creep fault zones according to claim 1, characterized in that: The thickness of the grouting reinforcement layer is one to two times the diameter of the creep fracture zone.

3. The hierarchical energy dissipation and excavation structure for tunnels crossing creep fault zones according to claim 1, characterized in that: The energy dissipation unit is composed of a rear part, a middle part and a front part of the energy dissipation unit, and the rear part, the middle part and the front part of the energy dissipation unit are an integrated demolding structure; the middle part of the energy dissipation unit includes a pressure relief chamber, a pressure relief liquid and solid rubber, the pressure relief liquid is placed in the pressure relief chamber, and the outside of the pressure relief chamber is wrapped by solid rubber; the front part of the energy dissipation unit includes a pressure relief hole, the end of the pressure relief chamber is connected to the pressure relief hole, and a pressure relief valve is provided in the pressure relief hole.

4. The hierarchical energy dissipation and excavation structure for tunnels crossing creep fault zones according to claim 1, characterized in that: The diameter of the multi-stage energy dissipation unit increases successively, the pressure threshold of the pressure relief valve of the energy dissipation unit decreases successively, and the capacity of the pressure relief cavity of the energy dissipation unit increases successively.

5. The hierarchical energy dissipation and excavation structure for tunnels crossing creep fault zones according to claim 1 is characterized in that: In the hierarchical energy dissipation system, the energy dissipation units at each level are fixedly connected by an adhesive, and the gaps are filled with rubber particles and fixed by the adhesive.

6. A tunnel excavation method using the graded energy dissipation excavation structure for tunnel crossing a creep fault zone according to any one of claims 1 to 5, characterized in that: The implementation steps of this excavation method are as follows: S1. Determine the specific mileage, scale and annual average activity rate of the creep fault zone; S2. Based on the specific mileage, scale, and annual average activity rate of the creep fault zone determined in step S1, advance tunnel excavation is performed to form a tunnel excavation section. S3. A grouting reinforcement layer, an expansion support layer, an energy dissipation layer, and a tunnel support layer are sequentially applied to the tunnel expansion section to form a graded energy dissipation expansion structure in the creep fault zone. The energy dissipation process of the graded energy dissipation and excavation structure is as follows: when creep dissipation occurs in the creep fault zone, the grouting reinforcement layer and the excavation support layer consume the creep dissipation strain energy through extrusion deformation; when the creep dissipation strain energy exceeds the bearing capacity of the grouting reinforcement layer and the excavation support layer, the longitudinal energy dissipation joints of the energy dissipation layer evenly distribute the creep dissipation strain energy to each graded energy dissipation system; as the creep dissipation strain energy continues to accumulate, each energy dissipation unit dissipates the strain energy in turn by releasing pressure relief fluid. When the dislocation value of the creep dislocation in the creep fault zone reaches the design value of the graded energy dissipation and excavation expansion structure, the pressure relief fluid in the graded energy dissipation system is completely discharged, and the accumulated creep dislocation strain energy is jointly borne by the energy dissipation unit and the tunnel support layer.

Images