GRADIENT LINING STRUCTURE OF TRAFFIC TUNNEL CROSSING ACTIVE FAULT AND CONSTRUCTION METHOD THEREOF

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The application claims priority to Chinese patent application No. 2024115481008, filed on Nov. 1, 2024, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

This disclosure relates to the technical field of tunnel engineering, and in particular, to a gradient lining structure of a traffic tunnel crossing an active fault and a construction method thereof.

BACKGROUND

When highway and railway tunnels are constructed or planned in high-intensity seismic zones of western China, many long and large tunnels inevitably need to cross active fault zones. Past tunnel seismic damage data indicates that fault movement can cause severe damage to the tunnel and disruption of lines, posing a huge threat to tunnel safety and normal traffic order.

Fault dislocation deformation is a non-uniform deformation, and the deformation rate follows a variation law where the dislocation quantity at the main sliding face is large and gradually decreases towards both sides of the main sliding face. The greater the dislocation deformation rate, the greater the stress on the secondary lining layer. Currently, the seismic resistance/anti-dislocation technologies for tunnels crossing active faults include: performing over-excavation to reserve deformation space, enhancing deformation capacity of segmented linings, and installing shock-absorbing layers for buffering and energy absorption, etc. However, the existing over-excavation, segmented, and shock-absorbing structures have all failed to take into account the dislocation deformation mode of active faults, and the lining along a longitudinal direction of the tunnel is a uniform structure, when fault creep or stick-slip occurs, the stress on the lining structure is extremely uneven, and the main sliding surface is highly prone to severe damage, which poses a serious threat to tunnel and traffic safety. Meanwhile, in the prior art, the deformation joint in the secondary lining layer and the fault main sliding surface are arranged in an aligned manner, which leads to significant misalignment of the lining at the fault main sliding surface, resulting in damage to the lining structure, sharp changes in the tunnel pavement slope, and the vertical lane slope and horizontal line curvature exceeding the corresponding limits. The secondary lining within a certain range on both sides of the main sliding surface needs to be removed for repair, which involves great repair difficulty, long recovery time, and high economic costs.

Therefore, how to provide a gradient lining structure of a traffic tunnel crossing an active fault, such that when the lining undergoes gradual deformation under the action of fault movement, it can achieve the technical effects of preventing lining damage or misalignment and ensuring that the tunnel remains undamaged after fault movement or can be quickly opened to traffic after simple repair, is an urgent technical problem to be solved by those skilled in the art.

SUMMARY

In view of the problems existing in the prior art, the technical problem to be solved by this disclosure is to provide a lining structure adapted to the fault movement deformation mode, so that the lining structure has more uniform stress and deformation under fault movement, the structure is not damaged, the lane slope and line curvature meet relevant requirements, and rapid recovery of tunnel functions after an earthquake is achieved.

To achieve the above purpose, this disclosure provides a gradient lining structure of a traffic tunnel crossing an active fault. The gradient lining structure of a traffic tunnel crossing an active fault is located in a tunnel anti-dislocation fortification area, and the gradient lining structure of a traffic tunnel crossing an active fault includes: a surrounding rock reinforcing layer, the surrounding rock reinforcing layer being disposed along the full circumference of an inner wall of a tunnel surrounding rock; an initial supporting layer, the initial supporting layer being disposed along the full circumference of an inner wall of the surrounding rock reinforcing layer; a deformation absorption layer, the deformation absorption layer being disposed along the full circumference of an inner wall of the initial supporting layer; a secondary lining layer, the secondary lining layer being disposed along the full circumference of an inner wall of the deformation absorption layer; and a waterproof layer, the waterproof layer being arranged in an area above an arch portion of the tunnel, and the waterproof layer being located between the deformation absorption layer and the secondary lining layer.

In the first aspect, the surrounding rock reinforcing layer is obtained by anchoring and grouting reinforcement on the inner wall of the tunnel surrounding rock; and a radial dimension of the surrounding rock reinforcing layer is 3-5 m.

In the first aspect, the initial supporting layer is obtained by the full-circumference arrangement of a metal mesh and PVA fiber shotcrete; and a thickness of the initial supporting layer is the same as that of the initial supporting layer in a non-dislocation fortification area.

In the first aspect, the deformation absorption layer includes: an upper arch absorption layer, the upper arch absorption layer being located between the initial supporting layer and the waterproof layer; a lower arch absorption layer, the lower arch absorption layer being located in an inverted arch area below the arch portion of the tunnel, the lower arch absorption layer including a foam concrete layer and a pebble layer, and the foam concrete layer is located between the pebble layer and the secondary lining layer, where both the upper arch absorption layer and the foam concrete layer are filled with a foam concrete material; a thickness of the upper arch absorption layer is the same as that of the lower arch absorption layer, and a thickness of the foam concrete layer is the same as that of the pebble layer; and the thickness of the upper arch absorption layer is not greater than a ratio of fault fortification dislocation quantity to a compression rate of the foam concrete.

In the first aspect, the secondary lining layer includes a plurality of reinforced concrete segments, and each of the reinforced concrete segments is disposed along the full circumference of the inner wall of the surrounding rock reinforcing layer; and the plurality of reinforced concrete segments are arranged adjacently along a longitudinal direction of the tunnel, and a deformation joint is disposed between any two adjacent reinforced concrete segments.

This disclosure further provides a construction method of the gradient lining structure of a traffic tunnel crossing an active fault, where the construction method is used for the construction of the gradient lining structure of a traffic tunnel crossing an active fault, and the construction method includes: obtaining a geomechanical model of a surrounding rock in an active fault area based on geometric and motion characteristics of an active fault, physical and mechanical parameters of a fault zone surrounding rock, and a spatial relationship between a tunnel and a fault; obtaining a fault dislocation deformation distribution curve within an anti-dislocation fortification range of the tunnel based on a response calculation of a rock mass in the active fault area under fault fortification dislocation quantity; obtaining a fault dislocation deformation rate curve by taking a derivative of the obtained dislocation deformation distribution curve; and within the anti-dislocation fortification range of the tunnel, obtaining the gradient lining structure of a traffic tunnel crossing an active fault by disposing a surrounding rock reinforcing layer, an initial supporting layer, a deformation absorption layer, a waterproof layer, and a secondary lining layer in sequence from outside to inside based on the fault dislocation deformation rate curve.

In the second aspect, in a longitudinal direction of the tunnel, mechanical parameters of the surrounding rock reinforcing layer gradually decrease towards both sides from a fault main sliding surface; the rate at which the mechanical parameters decrease is consistent with the fault dislocation deformation rate; and the mechanical parameters include surrounding rock strength and elastic modulus.

In the second aspect, the volume content of PVC in the PVA fiber shotcrete of the initial supporting layer at a position of the fault main sliding surface is 0.7%; in the longitudinal direction of the tunnel, the volume content of PVC in the PVA fiber shotcrete of the initial supporting layer gradually decreases to 0% towards both sides from the fault main sliding surface; and a rate at which the volume content of the PVC decreases is consistent with the fault dislocation deformation rate.

In the second aspect, the density of foam concrete of the deformation absorption layer at the position of the fault main sliding surface is 300 kg/m³; in the longitudinal direction of the tunnel, the density of the foam concrete gradually increases to 700 kg/m³ towards both sides from the fault main sliding surface; and a rate at which the density of the foam concrete increases is consistent with the fault dislocation deformation rate.

In the second aspect, the length of a reinforced concrete segment of the secondary lining layer at the position of the fault main sliding surface is 4 m; in the longitudinal direction of the tunnel, the length of the reinforced concrete segment gradually increases to 12 m towards both sides from the fault main sliding surface; and a rate at which the length of the reinforced concrete segment increases is consistent with the fault dislocation deformation rate.

BENEFICIAL EFFECTS

according to this disclosure, within the anti-dislocation fortification range of the tunnel, the gradient lining structure of a traffic tunnel crossing the active fault is provided with a surrounding rock reinforcing layer, an initial supporting layer, a deformation absorption layer, a waterproof layer, and a secondary lining layer in sequence from outside to inside, where the surrounding rock reinforcing layer, the initial supporting layer, and the deformation absorption layer all adopt a gradient structure, so that after the fault dislocation deformation passes through the three gradient layers (i.e., the surrounding rock reinforcing layer, the initial supporting layer, and the deformation absorption layer), the surrounding rock deformation transmitted to the secondary lining layer is more uniform, and the stress on the secondary lining layer is more uniform; meanwhile, the length of the reinforced concrete segments of the secondary lining layer gradually increases towards both sides from the fault main sliding surface, so that the deformation of the secondary lining layer is more gradual, and the dislocation and destruction of the secondary lining layer are avoided; in addition, the part below the arch portion of the deformation absorption layer includes a foam concrete layer and a pebble layer, most of the deformation caused by fault dislocation can be absorbed by the foam concrete layer, the pebble layer can exhibit a certain degree of fluidity during the fault dislocation process, and the local non-uniform deformation of the secondary lining layer is buffered through the flow of the pebble layer, so that the curvature and slope of the secondary lining are gradually changed, thus ensuring that the pavement slope of the tunnel meets the driving requirements; it can be seen that a gradient lining structure adapted to fault dislocation is formed in this disclosure, which enables the secondary lining layer of the tunnel to be subjected to uniform stress and deformation, thereby avoiding misalignment and damage of secondary lining layer under fault movement; and enables the pavement slope of the tunnel to meet driving requirements, thereby ensuring the structure and driving safety of the tunnel crossing the active fault; and moreover, under the condition of the same fault fortification dislocation quantity, the gradient lining structure of a traffic tunnel crossing the active fault of this disclosure can effectively reduce the thickness of the deformation absorption layer by constructing the three gradient layers (i.e., the surrounding rock reinforcing layer, the initial supporting layer, and the deformation absorption layer) and arranging the foam concrete layer and the pebble layer in the area below the arch portion of the deformation absorption layer, which further reduces the excavation area of the tunnel, achieving better economic efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

To illustrate the technical solutions in the embodiments of this disclosure or in the prior art more clearly, the following briefly introduces the accompanying drawings to be used for describing the embodiments. Obviously, the accompanying drawings in the following description only show some embodiments of this disclosure, and those of ordinary skill in the art may still derive other accompanying drawings from these accompanying drawings without creative efforts.

FIG. 1 is a schematic diagram of a cross-sectional structure of a gradient lining structure of a traffic tunnel crossing an active fault according to this disclosure;

FIG. 2 is a schematic diagram of a longitudinal cross-sectional structure of a gradient lining structure of a traffic tunnel crossing an active fault according to this disclosure;

FIG. 3 is a fault dislocation deformation distribution curve diagram within an anti-dislocation fortification range of the tunnel according to this disclosure;

FIG. 4 is a fault dislocation deformation rate curve diagram according to this disclosure;

FIG. 5 is a deformation diagram of a gradient lining structure of a traffic tunnel crossing an active fault according to this disclosure after fault movement; and

FIG. 6 is a deformation diagram of a tunnel lining structure in the prior art after fault movement.

REFERENCE NUMERALS

• • 1. surrounding rock reinforcing layer; 2. tunnel surrounding rock; 3. initial supporting layer; 4. deformation absorption layer; 41. upper arch absorption layer; 42. lower arch absorption layer; 421. foam concrete layer; 422. pebble layer; 5. secondary lining layer; 51. reinforced concrete segment; 52. deformation joint; 6. waterproof layer; 7. fault main sliding surface; 8. pavement; 9. tunnel.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The technical solutions in the embodiments of this disclosure are clearly and completely described below with reference to the accompanying drawings in the embodiments of this disclosure. Obviously, the described embodiments are only some but not all of the embodiments of this disclosure. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the specification shall fall within the protection scope of this disclosure.

Embodiment 1

As shown in FIG. 1 to FIG. 2, Embodiment 1 provides a gradient lining structure of a traffic tunnel crossing an active fault. The gradient lining structure of a traffic tunnel crossing an active fault is located in a tunnel anti-dislocation fortification area, and the gradient lining structure of a traffic tunnel crossing an active fault includes: a surrounding rock reinforcing layer 1, the surrounding rock reinforcing layer 1 being disposed along the full circumference of an inner wall of a tunnel surrounding rock 2; an initial supporting layer 3, the initial supporting layer 3 being disposed along the full circumference of an inner wall of the surrounding rock reinforcing layer 1; a deformation absorption layer 4, the deformation absorption layer 4 being disposed along the full circumference of an inner wall of the initial supporting layer 3; a secondary lining layer 5, the secondary lining layer 5 being disposed along the full circumference of an inner wall of the deformation absorption layer 4; and a waterproof layer 6, the waterproof layer 6 being arranged in an area above an arch portion of the tunnel, and the waterproof layer 6 being located between the deformation absorption layer 4 and the secondary lining layer 5.

According to this disclosure, within the anti-dislocation fortification range of the tunnel, the gradient lining structure of a traffic tunnel crossing the active fault is provided with a surrounding rock reinforcing layer 1, an initial supporting layer 3, a deformation absorption layer 4, a waterproof layer 6, and a secondary lining layer 5 in sequence from outside to inside, where the surrounding rock reinforcing layer 1, the initial supporting layer 3, and the deformation absorption layer 4 all adopt a gradient structure, so that after the fault dislocation deformation passes through the three gradient layers (i.e., the surrounding rock reinforcing layer 1, the initial supporting layer 3, and the deformation absorption layer 4), the surrounding rock deformation transmitted to the secondary lining layer 5 is more uniform, and the stress on the secondary lining layer 5 is more uniform; meanwhile, the length of the reinforced concrete segments 51 of the secondary lining layer 5 gradually increases towards both sides from the fault main sliding surface 7, so that the deformation of the secondary lining layer 5 is more gradual, and the dislocation and destruction of the secondary lining layer 5 are avoided; in addition, the part below the arch portion of the deformation absorption layer 4 includes a foam concrete layer 421 and a pebble layer 422, most of the deformation caused by fault dislocation can be absorbed by the foam concrete layer 421, the pebble layer 422 can exhibit a certain degree of fluidity during the fault dislocation process, and the local non-uniform deformation of the secondary lining layer 5 is buffered through the flow of the pebble layer 422, so that the curvature and slope of the secondary lining are gradually changed, thus ensuring that the pavement 8 slope of the tunnel 9 meets the driving requirements; it can be seen that a gradient lining structure adapted to fault dislocation is formed in this disclosure, which enables the secondary lining layer 5 of the tunnel 9 to be subjected to uniform stress and deformation, thereby avoiding misalignment and damage of secondary lining layer 5 under fault movement; and enables the pavement 8 slope of the tunnel 9 to meet driving requirements, thereby ensuring the structure and driving safety of the tunnel crossing the active fault; and moreover, under the condition of the same fault fortification dislocation quantity, the gradient lining structure of a traffic tunnel crossing the active fault of this disclosure can effectively reduce the thickness of the deformation absorption layer 4 by constructing the three gradient layers (i.e., the surrounding rock reinforcing layer 1, the initial supporting layer 3, and the deformation absorption layer 4) and arranging the foam concrete layer 421 and the pebble layer 422 in the area below the arch portion of the deformation absorption layer 4, which further reduces the excavation area of the tunnel 9, achieving better economic efficiency.

In some possible implementations, the surrounding rock reinforcing layer 1 is obtained by anchoring and grouting reinforcement on the inner wall of the tunnel surrounding rock 2; and a radial dimension of the surrounding rock reinforcing layer 1 is 3-5 m.

Specifically, an anchored grouting anchor rod is inserted into the tunnel surrounding rock 2, and concrete slurry is injected into the tunnel surrounding rock 2 through the grouting anchor rod, which is used for reinforcing the tunnel surrounding rock 2, and is used for buffering the force transmitted to the secondary lining layer 5, making the stress on the secondary lining layer 5 more uniform.

In some possible implementations, the initial supporting layer 3 is obtained by the full-circumference arrangement of a metal mesh and PVA fiber shotcrete; and a thickness of the initial supporting layer 3 is the same as that of the initial supporting layer in a non-dislocation fortification area.

Specifically, the metal mesh is arranged along the full circumference of the surrounding rock reinforcing layer 1. The PVC fiber shotcrete is sprayed onto the metal mesh to form a metal mesh concrete structure, so that the initial supporting layer 3 is constituted, and the initial supporting layer 3 plays a supporting role. In addition, the volume content of PVC in the PVC fiber shotcrete of the initial supporting layer 3 is variable, with the volume content of PVC ranging from 0 to 0.7%, which enhances the effect of the initial supporting layer 3 in buffering the force transmitted to the secondary lining layer 5, making the stress on the secondary lining layer 5 more uniform.

In some possible implementations, the deformation absorption layer 4 includes: an upper arch absorption layer 41, the upper arch absorption layer 41 being located between the initial supporting layer 3 and the waterproof layer 6; a lower arch absorption layer 42, the lower arch absorption layer 42 being located in an inverted arch area below the arch portion of the tunnel, the lower arch absorption layer 42 including a foam concrete layer 421 and a pebble layer 422, and the foam concrete layer 421 is located between the pebble layer 422 and the secondary lining layer 5, where both the upper arch absorption layer 41 and the foam concrete layer 421 are filled with a foam concrete material; a thickness of the upper arch absorption layer 41 is the same as that of the lower arch absorption layer 42, and a thickness of the foam concrete layer 421 is the same as that of the pebble layer 422; and the thickness of the upper arch absorption layer 41 is not greater than a ratio of fault fortification dislocation quantity to a compression rate of the foam concrete.

Specifically, the upper arch absorption layer 41 is entirely filled with foam concrete, and the foam concrete layer 421 of the lower arch absorption layer 42 is filled with foam concrete, which can buffer the force transmitted to the secondary lining layer 5 and absorb most of the deformation caused by fault dislocation, making the stress on the secondary lining layer 5 more uniform. Meanwhile, the pebble layer 422 of the lower arch absorption layer 42 located between the foam concrete layer 421 and the secondary lining layer 5 can exhibit a certain degree of fluidity during the fault dislocation process, and the local non-uniform deformation of the secondary lining layer 5 is buffered through the flow of the pebble layer 422, so that the curvature and slope of the secondary lining are gradually changed, thus ensuring that the pavement 8 slope of the tunnel 9 meets the driving requirements.

In some possible implementations, the secondary lining layer 5 includes a plurality of reinforced concrete segments 51, and each of the reinforced concrete segments 51 is disposed along the full circumference of the inner wall of the surrounding rock reinforcing layer 1; and the plurality of reinforced concrete segments 51 are arranged adjacently along a longitudinal direction of the tunnel, and a deformation joint 52 is disposed between any two adjacent reinforced concrete segments 51.

Specifically, the length of the reinforced concrete segment 51 of the secondary lining layer 5 varies in the longitudinal direction of the tunnel. The length of the reinforced concrete segment 51 ranges from 4 to 12 m, and the average length is relatively large, which improves the economic efficiency of the gradient lining structure of a traffic tunnel crossing an active fault. In addition, in this disclosure, the length of the reinforced concrete segment 51 at the fault main sliding surface 7 is set to 4 m, the length is relatively short, and a deformation joint 52 is arranged between any two adjacent reinforced concrete segments 51. The deformation joint 52 and the fault main sliding surface 7 are arranged in a staggered manner, so that when the fault dislocation quantity is greater than the fault fortification dislocation quantity, the gradient lining structure can limit the damage range of the secondary lining layer 5 within 4 m, featuring a small damage range and easy repair.

Embodiment 2

As shown in FIG. 1 to FIG. 6, Embodiment 2 of this disclosure provides a construction method of the gradient lining structure of a traffic tunnel crossing an active fault, where the construction method is used for the construction of the gradient lining structure of a traffic tunnel crossing an active fault according to the Embodiment 1, and the construction method includes: obtaining a geomechanical model of a surrounding rock in an active fault area based on geometric and motion characteristics of an active fault, physical and mechanical parameters of a fault zone surrounding rock, and a spatial relationship between a tunnel and a fault; obtaining a fault dislocation deformation distribution curve within an anti-dislocation fortification range of the tunnel based on a response calculation of a rock mass in the active fault area under fault fortification dislocation quantity; obtaining a fault dislocation deformation rate curve by taking a derivative of the dislocation deformation distribution curve; and within the anti-dislocation fortification range of the tunnel, obtaining the gradient lining structure of a traffic tunnel crossing an active fault by disposing a surrounding rock reinforcing layer, an initial supporting layer, a deformation absorption layer, a waterproof layer, and a secondary lining layer in sequence from outside to inside based on the fault dislocation deformation rate curve.

Specifically, the fault dislocation deformation rate curve has an important role in constructing the gradient lining structure of a traffic tunnel crossing an active fault of this disclosure. In this disclosure, mechanical parameters of the surrounding rock reinforcing layer gradually decrease towards both sides from the fault main sliding surface; the volume content of PVC in the PVA fiber shotcrete of the initial supporting layer gradually decreases towards both sides from the fault main sliding surface; the density of the foam concrete of the deformation absorption layer gradually increases towards both sides from the fault main sliding surface; and the length of the reinforced concrete segment of the secondary lining layer gradually increases towards both sides from the fault main sliding surface. The above-mentioned decreasing and increasing rates are consistent with the fault dislocation deformation rate, so that the gradient lining structure of a traffic tunnel crossing an active fault of this disclosure is adapted to fault movement deformation mode of the active fault. The gradient lining structure of a traffic tunnel crossing an active fault of this disclosure is gradually changed, and the lining is gradually deformed under the effect of fault movement, which prevents the lining structure from being damaged or misaligned, so that the lining structure has more uniform stress and deformation under fault movement, the structure is not damaged, and the lane slope and line curvature meet relevant requirements, achieving the technical effects that the tunnel remains undamaged after fault movement or can be quickly opened to traffic after simple repair.

It should be noted that the construction method of the gradient lining structure of a traffic tunnel crossing an active fault in Embodiment 2 is used for the construction of the gradient lining structure of a traffic tunnel crossing an active fault according to the Embodiment 1. Therefore, the performance principle of gradient lining structure of a traffic tunnel crossing an active fault will not be repeated herein, and reference may be made to Embodiment 1 for a part that is not described in detail.

In some possible implementations, in a longitudinal direction of the tunnel, mechanical parameters of the surrounding rock reinforcing layer gradually decrease towards both sides from a fault main sliding surface; the rate at which the mechanical parameters decrease is consistent with the fault dislocation deformation rate; the mechanical parameters include surrounding rock strength and elastic modulus; the volume content of PVC in the PVA fiber shotcrete of the initial supporting layer at a position of the fault main sliding surface is 0.7%; in the longitudinal direction of the tunnel, the volume content of PVC in the PVA fiber shotcrete of the initial supporting layer gradually decreases to 0% towards both sides from the fault main sliding surface; a rate at which the volume content of the PVC decreases is consistent with the fault dislocation deformation rate; the density of foam concrete of the deformation absorption layer at the position of the fault main sliding surface is 300 kg/m³; in the longitudinal direction of the tunnel, the density of the foam concrete gradually increases to 700 kg/m³ towards both sides from the fault main sliding surface; a rate at which the density of the foam concrete increases is consistent with the fault dislocation deformation rate; the length of a reinforced concrete segment of the secondary lining layer at the position of the fault main sliding surface is 4 m; in the longitudinal direction of the tunnel, the length of the reinforced concrete segment gradually increases to 12 m towards both sides from the fault main sliding surface; and a rate at which the length of the reinforced concrete segment increases is consistent with the fault dislocation deformation rate.

Specifically, mechanical parameters of the surrounding rock reinforcing layer gradually decrease towards both sides from the fault main sliding surface; the volume content of PVC in the PVA fiber shotcrete of the initial supporting layer gradually decreases towards both sides from the fault main sliding surface; and the density of the foam concrete of the deformation absorption layer gradually increases towards both sides from the fault main sliding surface, which are gradually changed. The above-mentioned decreasing rate and increasing rate are consistent with the fault dislocation deformation rate, allowing the gradient structures of the surrounding rock reinforcing layer, the initial supporting layer, and the deformation absorption layer to adapt to the fault movement deformation mode, so that the surrounding rock deformation transmitted to the secondary lining layer is more uniform, and the stress on the secondary lining layer is more uniform. The lining structure is prevented from being damaged or misaligned, so that the lining structure has more uniform stress and deformation under fault movement, the structure is not damaged, and the lane slope and line curvature meet relevant requirements, achieving the technical effects that the tunnel remains undamaged after fault movement or can be quickly opened to traffic after simple repair. Meanwhile, the three gradient layers (i.e., the surrounding rock reinforcing layer, the initial supporting layer, and the deformation absorption layer) are constructed and the foam concrete layer and the pebble layer are arranged in the area below the arch portion of the deformation absorption layer, which effectively reduces the thickness of the deformation absorption layer, and further reduces the excavation area of the tunnel, achieving better economic efficiency. In addition, the average length of the reinforced concrete segment is relatively large, which improves the economic efficiency of the gradient lining structure of a traffic tunnel crossing an active fault. Meanwhile, the length of the reinforced concrete segment at the fault main sliding surface is set to 4 m, the length is relatively short, and a deformation joint is arranged between any two adjacent reinforced concrete segments. The deformation joint and the main sliding surface are arranged in a staggered manner, so that when the fault dislocation quantity is greater than the fault fortification dislocation quantity, the gradient lining structure can limit the damage range of the secondary lining layer within 4 m, featuring a small damage range and easy repair.

In order to further describe the technical solutions of this disclosure in further detail to support the technical problems to be solved by this disclosure, the following describes the preparation method in detail as an Example 1.

EXAMPLE 1

Background

• • A highway tunnel adopts a circular cross-section, and a line crosses an active fault vertically. The active fault is a normal fault with an inclination angle of 50 degrees; the fortification fault dislocation quantity is 50 cm; and the net clear radius of the tunnel is 6.5 m. In the non-fortified section, the initial support of the tunnel adopts a C30 shotcrete structure with a thickness of 30 cm, and the secondary lining adopts a C40 reinforced concrete structure with a thickness of 50 cm.

A construction method of the gradient lining structure of a traffic tunnel crossing an active fault includes:

• • obtaining a three-dimensional finite element model of the rock mass in the active fault area based on geometric and motion characteristics of an active fault, physical and mechanical parameters of a fault zone surrounding rock, and a spatial relationship between a tunnel and a fault; obtaining a fault dislocation deformation distribution curve within an anti-dislocation fortification range of the tunnel based on a deformation calculation of a rock mass under the fault fortification dislocation quantity; and obtaining a fault dislocation deformation rate curve by taking a derivative of the dislocation deformation distribution curve; and
  • within the anti-dislocation fortification range of the tunnel, obtaining the gradient lining structure of a traffic tunnel crossing an active fault by disposing a surrounding rock reinforcing layer, an initial supporting layer, a deformation absorption layer, a waterproof layer, and a secondary lining layer in sequence from outside to inside based on the fault dislocation deformation rate curve.

A parameter construction process for arranging the gradient lining structure of a traffic tunnel crossing an active fault includes:

• • within the anti-dislocation fortification range of the tunnel, based on a distance from the fault main sliding surface in the fault dislocation deformation rate curve, partitioning the surrounding rock reinforcing layer, the initial supporting layer, and the deformation absorption layer, and dividing into 10 areas with a length of 3 m along the longitudinal direction of the tunnel, and the 10 areas being respectively: −21 m˜−18 m, −18 m˜−15 m, −15 m˜−12 m,-12 m˜−9 m, −9 m˜−6 m, −6 m˜−3 m, −3m˜0 m, 0 m˜3 m, 3 m˜6 m, 6 m˜9 m, where the negative number represents the distance from the fault main sliding surface to the left, and the positive number represents the distance from the fault main sliding surface to the right;
  • arranging the surrounding rock reinforcing layer along the full circumference of the tunnel surrounding rock by means of anchoring and grouting reinforcement, the thickness of the surrounding rock reinforcing layer being 5 m; and adjusting the surrounding rock strength and the elastic modulus of the surrounding rock reinforcing layer reinforced by the grouting, so that a reinforced uniaxial compressive strength of the surrounding rock reinforcing layer in a corresponding area of the fault main sliding surface is not less than 10 MPa, and the surrounding rock strength and the elastic modulus of the surrounding rock reinforcing layer of the remaining nine areas on both sides gradually decrease according to the deformation rate of the fault dislocation deformation rate curve;
  • arranging the initial supporting layer along the full circumference of the surrounding rock reinforcing layer, the initial supporting layer being composed of a C30 metal mesh and PVA fiber shotcrete, and the thickness of the initial supporting layer being consistent with that of the non-fortified section; and the volume content of PVC in the PVA fiber shotcrete in the area corresponding to the fault main sliding surface being set to 0.7%, and based on the fault dislocation deformation rate curve, the volume content of PVC in the 10 areas from left to right being respectively: 0.068%, 0.12%, 0.145%, 0.15%, 0.18%, 0.23%, 0.7%, 0.52%, 0.29%, and 0.05%;
  • arranging the deformation absorption layer along the full circumference of the initial supporting layer, and based on the fault fortification dislocation quantity of 50 cm and the average compression rate of the foam concrete is about 70%, the thickness of the deformation absorption layer being not greater than 71 cm that is a ratio of the fault fortification dislocation quantity to the average compression rate of the foam concrete; the thickness of the deformation absorption layer being set to 60 cm, the thickness of the upper arch absorption layer being 60 cm, the thickness of the foam concrete layer being 30 cm, and the thickness of the pebble layer being 30 cm; and the density of the foam concrete material in the area corresponding to the fault main sliding surface being set to 300 kg/m³, and based on the fault dislocation deformation rate curve, the densities of the foam concrete material in the 10 areas from left to right being respectively: 700 kg/m³, 660 kg/m³, 650 kg/m³, 640 kg/m³, 620 kg/m³, 590 kg/m³, 300 kg/m³, 400 kg/m³, 550 kg/m³, and 700 kg/m³;
  • arranging the waterproof layer along the upper arch absorption layer, the layout of the waterproof layer being consistent with that of the normal section, and the waterproof layer being composed of a geotextile and an EVA waterproof plate;
  • arranging the secondary lining layer using C40 reinforced concrete, and the thickness of the secondary lining layer being consistent with that of the non-fortified section; the deformation joint of the secondary lining layer and the fault main sliding surface being arranged in a staggered manner, allowing the fault main sliding surface to be located in the middle of the reinforced concrete segment; the length of the reinforced concrete segment in the area corresponding to the fault main sliding surface being set to 4 m, and a vault of the tunnel is aligned with the deformation joint of the inverted arch portion; and based on the fault dislocation deformation rate curve, the lengths of the reinforced concrete segments in the 10 areas from left to right being respectively: 12 m, 10 m, 4 m, 4 m, 6 m, 9 m, and 12 m; and
  • based on the determined thickness of the initial supporting layer, the thickness of the deformation absorption layer, the thickness of the secondary lining layer, and the net clear radius of the tunnel being 30 cm, 60 cm, 50 cm, and 6.5 m, respectively, obtaining that the excavation radius of the tunnel in the fortified section is 7.9 m.

Conclusion: the schematic diagram of the gradient lining structure of a traffic tunnel crossing an active fault obtained through construction in the above Example 1 is shown in FIG. 1 to FIG. 2; the fault dislocation deformation distribution curve during the construction process is shown in FIG. 3; the fault dislocation deformation rate curve is shown in FIG. 4; after the occurrence of fault movement, the deformation diagram of the gradient lining structure of a traffic tunnel crossing an active fault of this disclosure is shown in FIG. 5; it can be seen from FIG. 5 that after the gradient lining structure of a traffic tunnel crossing an active fault occurs the fault movement, the deformation of the secondary lining layer is gradual, the secondary lining layer is not misaligned and damaged, and at the same time, the lining curvature and slope are gradually changed, ensuring that the pavement slope of the tunnel meets the driving requirements; however, in the prior art, the lining structure of the tunnel lining has obvious misalignment and damage after the fault movement occurs, as shown in FIG. 6; it can be seen that the gradient lining structure of a traffic tunnel crossing an active fault of this disclosure can achieve uniform stress and deformation of the tunnel lining structure, thereby avoiding misalignment and damage of the lining structure under fault movement; and enable the pavement slope of the tunnel to meet driving requirements, thereby ensuring the structure and driving safety of the tunnel crossing the active fault.

The above provides a detailed description of the preferred embodiments of this disclosure. It should be understood that those skilled in the art can from the many modifications and changes according to the concept of this disclosure without creative efforts. Therefore, any technical solution that can be obtained by those skilled in the art according to the concept of this disclosure through logical analysis, logical inference, or limited experiments on the basis of the prior art shall fall within the scope of protection determined by the claims.