Bridge-tunnel joint structure and construction method suitable for clay stratum

Abstract

The application relates to a bridge-tunnel joint structure and a construction method suitable for the structure under a clay layer, which comprises a special-shaped abutment, a rectangular bridge pier, a reinforced concrete portal wall, a self-advancing hollow grouting anchor rod and an inverted arch bottom grouting reinforcing structure. The special-shaped abutment is located outside the tunnel portal, the bottom is grouted to reinforce the clay layer, and the top is connected with the portal wall; the rectangular bridge piers are symmetrically arranged on both sides of the portal, the bottom is embedded into the rock by more than 2m, and the bridge piers have the functions of bridge support and tunnel anti-slide pile; the portal wall is vertically arranged on the top of the abutment and is welded with the exposed end of the self-advancing anchor rod which is distributed in a grid shape, and the tail end of the anchor rod is anchored into the portal wall by more than 0.5m; the inverted arch bottom grouting forms a consolidated layer and reinforces the clay layer. The application has the following characteristics: the bridge pier is used as an anti-slide pile, and 40% of the soil excavation is reduced; double reinforcement reduces the settlement of the portal wall by 90%; the inverted arch grouting improves the bearing capacity by 30%, reduces the risk of cracks and seepage water, and the self-advancing anchor rod reduces 3-4 processes and shortens the construction period.

Description

Technical Field

[0001] The present invention relates to the field of tunnel engineering technology, and specifically to a bridge-tunnel connection structure and construction method suitable for use under clay strata. The invention is particularly suitable for scenarios where the stratum at the entrance of a shallow tunnel is unstable, the portal wall is prone to sinking, and the later structure is prone to cracking. Background Art

[0002] When constructing a tunnel portal in clay strata, the following technical difficulties are often encountered:

[0003] 1. Insufficient side slope stability: The clay layer has poor permeability, and the surface grouting reinforcement effect is weak. Traditional anti-slide piles only solve the problem of slope stability but cannot prevent cracking of the tunnel structure.

[0004] 2. High risk of portal wall subsidence: Clay strata have creep characteristics, and traditional portal structure foundations are prone to sinking due to soil settlement;

[0005] 3. Tunnel structure cracking and water leakage: Cracks appear in the lining of open and concealed tunnels due to ground deformation, causing water leakage and affecting the durability of the structure.

[0006] Conventional solutions (such as surface grouting and independent anti-slide piles) currently offer limited functionality, poor environmental performance (requiring additional excavation for anti-slide piles), and insufficient long-term adaptability. These solutions are unable to simultaneously address slope stability, portal settlement, and structural cracking. Therefore, the development of a composite structure and supporting construction methods that integrate the functions of a bridge and tunnel is urgently needed. Summary of the Invention

[0007] The present invention aims to solve the technical problems of instability of the upslope of the tunnel portal, sinking of the portal wall and cracking of the tunnel structure in clay strata, and to provide a bridge-tunnel connection structure and construction method suitable for use under clay strata that has the functions of bridge support, slope reinforcement and structural crack resistance.

[0008] A bridge-tunnel connection structure suitable for use under clay strata, comprising a special-shaped abutment, a rectangular pier, a reinforced concrete portal wall, a self-propelled hollow grouting anchor rod, and a grouting reinforcement structure at the bottom of an inverted arch;

[0009] The special-shaped abutment is located outside the tunnel entrance, the bottom of the special-shaped abutment is reinforced with clay strata through a small grouting pipe, and the top is fixedly connected to the bottom of the reinforced concrete portal wall;

[0010] The rectangular piers are symmetrically arranged on both sides of the tunnel entrance and penetrate into the bedrock by at least 2 meters. The top of the rectangular pier supports the bridge structure, and the bottom is embedded in the clay layer and extends below the tunnel arch waist, serving as both bridge support and tunnel entrance anti-slip piles.

[0011] The reinforced concrete portal wall is vertically arranged on the top of the special-shaped abutment, and the upward slope of the reinforced concrete portal wall is welded and fixed to the exposed end of the self-propelled hollow grouting anchor rod;

[0012] The self-propelled hollow grouting anchor rods are distributed in a grid pattern on the tunnel upslope, and the ends of the self-propelled hollow grouting anchor rods are anchored at least 0.5m into the reinforced concrete portal wall;

[0013] The grouting reinforcement structure at the bottom of the inverted arch is a grouting consolidation layer below the inverted arch, which is formed by grouting and reinforcing the clay layer at the bottom of the inverted arch.

[0014] Furthermore, the rectangular pier is a reinforced concrete structure with a cross-sectional size of length*width≥2.0m*1.5m, the bottom is embedded in the clay layer to a depth of 1.2-1.5 times the tunnel diameter, and bidirectional shear steel bars are configured inside.

[0015] Furthermore, the concrete strength grade of the special-shaped abutment is ≥C35, the spacing of the small grouting pipes at the bottom is 0.8-1.0m, the grouting pressure is 0.5-1.0MPa, and the slurry is cement-water glass double liquid slurry.

[0016] Furthermore, the self-propelled hollow grouting anchor rod has a length of ≥8m, a spacing of ≤2m×2m, a diameter of ≥50mm, a grouting pressure of 0.3-0.5MPa, a slurry diffusion radius of ≥0.8m, and the exposed end and the steel cage of the reinforced concrete portal wall are double-sided welded, with a weld length of ≥10d, where d is the anchor rod diameter of the self-propelled hollow grouting anchor rod.

[0017] Furthermore, the bottom grouting reinforcement structure of the inverted arch is formed by using double-liquid grouting to reinforce the soil.

[0018] A construction method for a bridge-tunnel junction structure under a clay layer as described above comprises the following steps:

[0019] S1: Ground reinforcement and rectangular pier construction

[0020] Self-propelled hollow grouting anchors are used to reinforce the tunnel's upslope surface. The anchor length is ≥8m, the spacing is ≤2m×2m, the grouting pressure is 0.3-0.5MPa, and the reinforcement range extends to the tunnel waist.

[0021] Rectangular piers are constructed symmetrically on both sides of the tunnel entrance. The bottom of the piers is embedded in the clay layer to a depth of 1.2-1.5 times the tunnel diameter. The concrete strength is ≥ C40. Two-way shear reinforcement is configured inside. The rectangular piers are embedded in the bedrock for at least 2m.

[0022] S2: Side slope excavation and special-shaped abutment construction

[0023] Excavate the slope in layers to the designed elevation, with each layer excavation height ≤1.5m. Immediately after excavation, install advance pipe shed protection, with a length of ≥30m and annular spacing of ≤0.4m.

[0024] The soil beneath the special-shaped abutments is reinforced with small grouting pipes, with a spacing of 0.8-1.0m and a grouting pressure of 0.5-1.0MPa.

[0025] Tie up the special-shaped abutment reinforcement cage and pour C35 or above concrete to form the special-shaped abutment;

[0026] S3: Portal wall anchoring and pouring

[0027] The back slope is reinforced with secondary self-propelled hollow grouting anchor bolts, with an anchor bolt length of ≥8m and an exposed area of ​​≥0.5m;

[0028] Tie the steel cage of the reinforced concrete portal wall and weld the exposed end of the self-propelled hollow grouting anchor to the steel cage on both sides. The weld length should be ≥10d, where d is the diameter of the anchor.

[0029] Pour C40 or above concrete to form reinforced concrete portal walls, which are fixedly connected to the top of the special-shaped abutment;

[0030] S4: Tunnel excavation and invert reinforcement

[0031] The tunnel is excavated using the step method, and small system grouting pipes are installed in the arch and side walls. The system grouting pipes are ≥3.5m long, with annular spacing ≤1.0m, and are arranged in a plum blossom shape.

[0032] After the tunnel invert arch is excavated, the clay layer at the bottom of the invert arch is reinforced by grouting with a grouting pressure of 0.8-1.2MPa to form a grouting reinforcement layer at the bottom of the invert arch;

[0033] The main structure of the tunnel adopts a composite lining structure and is constructed according to the conventional reserved core soil method, with the primary support, waterproof layer and reinforced reinforced concrete secondary lining structure constructed at one time.

[0034] Compared with the prior art, the present invention has the following innovations and technical effects:

[0035] (1) Environmental protection and economy: Existing bridge piers are used as anti-slide piles, eliminating the need for additional anti-slide piles. This reduces the number of anti-slide piles required and reduces soil excavation by approximately 40%;

[0036] (2) Improved structural stability: Dual reinforcement of the special-shaped abutment bottom grouting + self-propelled anchor bolts anchored into the portal wall. The portal wall is directly supported on the rectangular piers, and the bottom of the piers is embedded in the rock. The settlement of the portal wall can be ignored, reducing it by at least 90%;

[0037] (3) Enhanced crack resistance and waterproofing performance: Grouting reinforcement at the bottom of the invert arch increases the bearing capacity of the stratum by 30%. Combined with the rigid constraints of the portal wall, the incidence of cracks in the tunnel structure is reduced, and the risk of water leakage is significantly reduced.

[0038] (4) Construction convenience: Self-propelled grouting anchor rods are used to replace traditional anchor rod + grouting step-by-step construction, reducing 3-4 working steps and shortening the construction period. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a schematic overall cross-sectional view of a bridge-tunnel connection structure under a clay layer according to an embodiment of the present invention;

[0040] Figure 2 This is a schematic diagram of the connection structure between a rectangular pier and a special-shaped abutment according to an embodiment of the present invention;

[0041] Figure 3 Schematic diagram of the anchoring node between the self-advanced hollow grouting anchor rod and the portal wall according to an embodiment of the present invention;

[0042] Figure 4 This is a schematic structural diagram of a rectangular bridge pier according to an embodiment of the present invention;

[0043] Figure 5 Schematic diagram of the connection structure between the steel cage and the self-propelled hollow grouting anchor rod according to an embodiment of the present invention.

[0044] In the figure: 1-special-shaped abutment; 1-1-small grouting duct; 2-rectangular pier; 2-1-bidirectional shear reinforcement; 3-reinforced concrete portal wall; 3-1-reinforcement cage; 4-self-propelled hollow grouting anchor rod; 5-grouting reinforcement structure at the bottom of the inverted arch; 6-advanced pipe shed; 7-system grouting duct. DETAILED DESCRIPTION

[0045] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0046] See also Figures 1-5 An embodiment of the present invention provides a bridge-tunnel connection structure suitable for use under clay strata, including a special-shaped abutment 1, a rectangular pier 2, a reinforced concrete portal wall 3, a self-propelled hollow grouting anchor rod 4, and a grouting reinforcement structure 5 at the bottom of an inverted arch.

[0047] The special-shaped abutment 1 is located outside the tunnel entrance. Its bottom is reinforced with clay soil via a small grouting conduit 1-1, and its top is fixedly connected to the bottom of the reinforced concrete portal wall 3. The concrete strength grade of the special-shaped abutment 1 is ≥ C35. The spacing between the small grouting conduits 1-1 at the bottom is 0.8-1.0m, and the grouting pressure is 0.5-1.0MPa. The grouting liquid is a cement-water glass dual-liquid slurry.

[0048] The rectangular piers 2 are arranged symmetrically along both sides of the tunnel entrance and penetrate into the bedrock by no less than 2m; the top of the rectangular pier 2 supports the bridge structure, and the bottom is embedded in the clay layer and extends below the tunnel arch waist, having both bridge support and tunnel entrance anti-slip pile functions; the rectangular pier 2 is a reinforced concrete structure with a cross-sectional dimension of length*width ≥2.0m*1.5m, the depth of the bottom embedded in the clay layer is 1.2-1.5 times the tunnel diameter, and bidirectional shear steel bars 2-1 are configured inside.

[0049] The reinforced concrete portal wall 3 is vertically arranged on the top of the special-shaped abutment 1, and the upward slope of the reinforced concrete portal wall 3 is welded and fixed to the exposed end of the self-propelled hollow grouting anchor rod 4; the self-propelled hollow grouting anchor rod 4 has a length ≥8m, a spacing ≤2m×2m, a diameter ≥50mm, a grouting pressure of 0.3-0.5MPa, a slurry diffusion radius ≥0.8m, and the exposed end is double-sidedly welded to the steel cage 3-1 of the reinforced concrete portal wall 3, with a weld length ≥10d, where d is the anchor rod diameter of the self-propelled hollow grouting anchor rod 4.

[0050] The self-propelled hollow grouting anchor rods 4 are distributed in a grid pattern on the tunnel upslope, and the ends of the self-propelled hollow grouting anchor rods 4 are anchored at least 0.5 m into the reinforced concrete portal wall 3;

[0051] The inverted arch bottom grouting reinforcement structure 5 is a grouting consolidation layer below the inverted arch, formed by grouting and reinforcing the clay layer at the bottom of the inverted arch. Preferably, the inverted arch bottom grouting reinforcement structure 5 is formed by grouting and reinforcing the soil with double liquid slurry.

[0052] Example: A tunnel portal project in a clay layer

[0053] The tunnel diameter is 12m, the natural moisture content of the clay layer is 35%, and the bearing capacity is 120kPa. Problems such as side slope instability, portal wall subsidence, and structural cracking need to be addressed.

[0054] A construction method for a bridge-tunnel junction structure under a clay layer, comprising the following steps:

[0055] Step 1: Ground reinforcement and rectangular pier construction

[0056] Four pairs of φ50mm self-propelled hollow grouting anchors were used for surface reinforcement of the upslope. The anchor length was 10m, the spacing was 2m×2m, the grouting pressure was 0.4MPa, and the grouting radius was 0.8m. The anchors were reinforced up to the tunnel waist (buried depth 8m).

[0057] Rectangular piers 2 are constructed on both sides of the tunnel entrance, with a cross-sectional diameter of D2.0m and a bottom embedded in the ground at a depth of 15m (1.25 times the tunnel diameter). φ25mm bidirectional shear steel bars 2-1 (spacing 200mm) are configured and poured with C40 concrete.

[0058] Step 2: Excavation of side slope and construction of special-shaped abutments

[0059] Excavate the side slope in layers (1.2m per layer), and immediately install φ108mm advanced pipe shed 6 (32m in length, 0.4m in circumferential spacing) after excavation;

[0060] The soil below the special-shaped abutment 1 was reinforced with a φ42mm small grouting pipe 1-1 (spacing 0.8m, grouting pressure 0.8MPa, cement-water glass double liquid slurry);

[0061] Tie the special-shaped abutment reinforcement cage (main reinforcement φ28mm, spacing 150mm) and pour C35 concrete to form special-shaped abutment 1.

[0062] Step 3: Anchoring and pouring of portal wall

[0063] A φ50mm self-propelled hollow grouting anchor bolt (length 10m, exposed 0.6m) was installed on the back slope for the second time.

[0064] Tie up the portal wall reinforcement cage 3-1 (main reinforcement φ25mm, spacing 150mm), and weld the exposed ends of the self-propelled hollow grouting anchor rods 4 to the reinforcement cage 3-1 on both sides (weld length 250mm);

[0065] C40 concrete is poured to form a reinforced concrete portal wall 3, which is tightly connected to the top of the special-shaped abutment 1.

[0066] Step 4: Tunnel excavation and invert reinforcement

[0067] The tunnel was excavated using the three-step method, with seven φ42mm system grouting pipes (4m long, 0.5m circumferential spacing) arranged in a plum blossom pattern on the arch and side walls.

[0068] After the inverted arch is excavated, the clay layer at the bottom of the inverted arch is reinforced with grouting (pressure 1.0 MPa) using a φ50 mm grouting small pipe (length 4 m, circumferential spacing 0.5 m, longitudinal spacing 1.0 m) to form a 2.5 m thick grouting consolidation layer 5;

[0069] The main structure of the tunnel adopts a composite lining structure and is constructed according to the conventional reserved core soil method, with the primary support, waterproof layer and reinforced reinforced concrete secondary lining structure constructed at one time.

[0070] According to on-site monitoring, the settlement of the portal wall was only 8 mm (25 mm in the conventional solution), no visible cracks appeared in the tunnel structure, and the water leakage rate was 0, which verified the technical effect of the present invention.

[0071] In summary, the present invention effectively solves the stability and durability problems of tunnel entrances in clay strata through structural innovation and construction method optimization, and has significant engineering application value.

[0072] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A bridge-tunnel connection structure suitable for use under clay strata, characterized in that: It includes a special-shaped abutment (1), a rectangular pier (2), a reinforced concrete portal wall (3), a self-propelled hollow grouting anchor rod (4) and a grouting reinforcement structure (5) at the bottom of the inverted arch; The special-shaped abutment (1) is located outside the tunnel entrance, the bottom of the special-shaped abutment (1) is reinforced with a clay layer through a grouting small conduit (1-1), and the top is fixedly connected to the bottom of the reinforced concrete portal wall (3); The rectangular bridge piers (2) are symmetrically arranged along both sides of the tunnel entrance and penetrate into the bedrock by no less than 2m; the top of the rectangular bridge piers (2) supports the bridge structure, and the bottom is embedded in the clay layer and extends below the tunnel arch waist, having both the functions of bridge support and tunnel entrance anti-sliding piles; The reinforced concrete portal wall (3) is vertically arranged on the top of the special-shaped abutment (1), and the upward slope of the reinforced concrete portal wall (3) is welded and fixed to the exposed end of the self-propelled hollow grouting anchor rod (4); The self-propelled hollow grouting anchor rods (4) are distributed in a grid pattern on the tunnel slope, and the ends of the self-propelled hollow grouting anchor rods (4) are anchored at least 0.5 m into the reinforced concrete portal wall (3); The inverted arch bottom grouting reinforcement structure (5) is a grouting consolidation layer below the inverted arch, formed by grouting and reinforcing the clay layer at the bottom of the inverted arch.

2. The bridge-tunnel connection structure suitable for use under clay strata according to claim 1, characterized in that: The rectangular pier (2) is a reinforced concrete structure with a cross-sectional dimension of length*width≥2.0m*1.5m, a bottom embedded in the clay layer to a depth of 1.2-1.5 times the tunnel diameter, and bidirectional shear reinforcement (2-1) is configured inside.

3. The bridge-tunnel connection structure suitable for use under clay strata according to claim 1, characterized in that: The concrete strength grade of the special-shaped abutment (1) is ≥C35, the spacing of the bottom grouting small conduits (1-1) is 0.8-1.0m, the grouting pressure is 0.5-1.0MPa, and the slurry is cement-water glass double liquid slurry.

4. The bridge-tunnel connection structure suitable for use under clay strata according to claim 1, characterized in that: The self-propelled hollow grouting anchor rod (4) has a length of ≥8m, a spacing of ≤2m×2m, a diameter of ≥50mm, a grouting pressure of 0.3-0.5MPa, a slurry diffusion radius of ≥0.8m, and an exposed end is double-sidedly welded to the steel cage (3-1) of the reinforced concrete portal wall (3), with a weld length of ≥10d, where d is the anchor rod diameter of the self-propelled hollow grouting anchor rod (4).

5. The bridge-tunnel connection structure suitable for use under clay strata according to claim 1, characterized in that: The inverted arch bottom grouting reinforcement structure (5) is formed by using double-liquid grouting to reinforce the soil.

6. A construction method for a bridge-tunnel junction structure under clay soil as claimed in any one of claims 1 to 5, characterized in that: The following steps are involved: S1: Ground reinforcement and rectangular pier construction (1) Use self-propelled hollow grouting anchor rods (4) to reinforce the tunnel slope surface. The anchor rod length is ≥8m, the spacing is ≤2m×2m, the grouting pressure is 0.3-0.5MPa, and the reinforcement range is up to the tunnel arch waist. (2) Rectangular piers (2) are constructed symmetrically on both sides of the tunnel entrance. The bottom of the pier is embedded in the clay layer to a depth of 1.2-1.5 times the tunnel diameter. The concrete strength is ≥ C40. Two-way shear reinforcement (2-1) is configured inside. The rectangular pier (2) is not less than 2m deep into the bedrock; S2: Side slope excavation and special-shaped abutment construction (1) Excavate the slope in layers to the design elevation, with the excavation height of each layer ≤1.5m. Immediately after excavation, install the advanced pipe shed (6) for protection, with the length of the pipe shed ≥30m and the circumferential spacing ≤0.4m; (2) The soil below the special-shaped abutment (1) is reinforced by grouting small pipes (1-1), with a spacing of 0.8-1.0m between the small pipes and a grouting pressure of 0.5-1.0MPa; (3) Tie the special-shaped abutment reinforcement cage and pour C35 or above concrete to form the special-shaped abutment (1); S3: Portal wall anchoring and pouring (1) The back slope is reinforced with a secondary self-propelled hollow grouting anchor (4), with the anchor length ≥8m and the exposed depth ≥0.5m; (2) Tie the steel cage (3-1) of the reinforced concrete portal wall (3) and weld the exposed end of the self-propelled hollow grouting anchor (4) to the steel cage (3-1) on both sides, with the weld length being ≥10d, where d is the diameter of the anchor; (3) pouring C40 or above concrete to form a reinforced concrete portal wall (3), which is fixedly connected to the top of the special-shaped abutment (1); S4: Tunnel excavation and invert reinforcement (1) The tunnel is excavated using the step method, and small system grouting pipes (7) are installed in the arch and side walls. The small system grouting pipes (7) have a length of ≥3.5m and a circumferential spacing of ≤1.0m, and are arranged in a plum blossom shape; (2) After the tunnel invert is excavated, the clay layer at the bottom of the invert is reinforced by grouting with a grouting pressure of 0.8-1.2 MPa to form a grouting reinforcement layer at the bottom of the invert (5); (3) The main structure of the tunnel adopts a composite lining structure, which is constructed according to the conventional reserved core soil method, and the primary support, waterproof layer and reinforced reinforced concrete secondary lining structure are constructed at one time.

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