Combined anti-lateral displacement pile foundation structure for shallow-buried tunnel in bias pressure stratum

Abstract

The utility model relates to underground engineering support technical field discloses a combination anti -side -shift pile foundation structure of shallow -buried tunnel bias pressure stratum aims at solving the problem of construction restriction, stress concentration, poor adaptability and high cost when traditional support technology is in response to bias pressure stratum. The structure includes plum blossom type arrangement's steel flower pipe pile group and top lightweight reinforced concrete retaining wall. Steel flower pipe pile is arranged perpendicularly along tunnel bias pressure side, and pile body is equipped with grouting hole, and forms reinforcing area through high -pressure grouting, and pile top is rigidly connected with retaining wall, and enhances overall stability. The retaining wall section is trapezoidal, and the bottom is embedded into the pile top, and realizes load continuous transmission. The combination anti -side -shift pile foundation structure of shallow -buried tunnel bias pressure stratum improves the anti -side -shift ability through pile -wall cooperation, restrains asymmetric deformation of soft soil layer, simultaneously simplifies construction procedure, shortens the period of construction, and reduces the project cost.

Description

Technical Field

[0001] This utility model relates to the field of underground engineering support technology, and in particular to a combined anti-lateral displacement pile foundation structure for shallow-buried tunnels with biased strata. Background Technology

[0002] In shallow tunnel construction, biased strata are a common geological condition. Due to differences in soil mechanical properties or topographic inclination, biased strata are prone to generating uneven lateral pressure, which significantly affects the tunnel support structure. This uneven pressure can cause lateral displacement and deformation of the tunnel lining, and even lead to instability, seriously threatening the safety and stability of the project.

[0003] Currently, in addressing the issue of biased soil pressure in shallow tunnels, traditional biased wall structures, such as reinforced concrete gravity retaining walls or diaphragm walls, are widely used. These structures are typically constructed close to the tunnel lining to resist lateral earth pressure. However, traditional methods have the following significant drawbacks and limitations:

[0004] 1. Construction limitations: The eccentric pressure wall must be constructed close to the tunnel outline, occupying a significant amount of excavation space. This is particularly problematic in narrow terrain or near existing structures, limiting construction flexibility. 2. Stress concentration issues: The rigid contact between the eccentric pressure wall and the tunnel lining can easily lead to localized stress concentration, potentially causing lining cracking or joint leakage, affecting the long-term durability of the structure. 3. Poor adaptability: The thickness and reinforcement of the eccentric pressure wall are usually fixed, making it difficult to adjust according to dynamic changes in earth pressure distribution. This can lead to material waste or insufficient reinforcement, failing to meet the actual needs under complex geological conditions. 4. Long construction period and high cost: Cast-in-place concrete walls require formwork, curing, and other procedures, resulting in a long construction period. Furthermore, removing temporary supports can easily disturb the strata, increasing construction risks and costs.

[0005] Although pile foundation alternatives are occasionally used in existing technologies, such as single-row vertical piles or symmetrical pile groups, these solutions have low lateral displacement resistance, cannot effectively match the asymmetric load characteristics of biased strata, and are difficult to form an overall coordinated force-bearing system.

[0006] Therefore, current technologies generally suffer from problems such as high construction difficulty, poor economic efficiency, and insufficient reliability when solving the problem of biased strata in shallow-buried tunnels. Utility Model Content

[0007] To address the aforementioned issues, this utility model provides a combined anti-lateral displacement pile foundation structure for shallow-buried tunnels with biased soil layers. This structure utilizes a quincunx-shaped pile group arrangement connected to a small retaining wall at the top to enhance anti-lateral displacement capabilities, simplify the construction process, and reduce project costs.

[0008] The technical solution adopted in this utility model is as follows:

[0009] A combined anti-lateral displacement pile foundation structure for shallow-buried tunnels in biased strata includes a retaining wall located on one side of the tunnel exterior, the retaining wall being fixed in position by a group of steel pipe piles; the steel pipe pile group includes multiple rows of drilled steel pipes arranged vertically along the biased side of the tunnel, the pile group being arranged in a staggered quincunx pattern; each drilled steel pipe is provided with a grouting hole, which, after being inserted into the ground for grouting, forms a grouting reinforcement zone below the retaining wall.

[0010] Furthermore, the retaining wall adopts a lightweight reinforced concrete structure with a trapezoidal cross-section. The longitudinal length of the retaining wall is the same as the length of the shallow buried biased section at the tunnel entrance. The bottom of the retaining wall is rigidly connected to the part of each drilled steel pipe that is exposed above the ground.

[0011] Furthermore, the drilled steel pipe is made of seamless steel pipe, which includes a bearing layer anchoring section and an embedded retaining wall depth section; several grouting holes are arranged axially in a staggered quincunx pattern on the bearing layer anchoring section of the drilled steel pipe, and the several grouting holes are arranged circumferentially at 60° staggered; a flange is provided at the top of the embedded retaining wall depth section of the drilled steel pipe, and several grouting valves are installed through the flange.

[0012] Furthermore, the section of the drilled steel pipe embedded in the retaining wall has no grouting holes, and an annular stiffening rib is provided at the connection between it and the anchoring section of the bearing layer. The annular stiffening rib is fitted onto the drilled steel pipe and is welded and fixed to the section of the drilled steel pipe embedded in the retaining wall and the steel mesh inside the retaining wall.

[0013] Furthermore, the bottom of the bearing layer anchorage section of the drilled steel pipe is a conical pile head.

[0014] The beneficial effects of this utility model are:

[0015] 1. Significantly Enhanced Lateral Misalignment Resistance: The staggered arrangement of the quincunx-shaped pile group, combined with the grouting reinforcement zone, forms a three-dimensional spatial anti-displacement system, significantly enhancing the lateral restraint of the soil. The synergistic force distribution of the pile group effectively disperses the asymmetric load on the biased strata, suppressing the lateral deformation tendency of weak soil layers and effectively preventing lateral displacement and instability of the tunnel lining. The pile tops and retaining walls are welded together with annular stiffening ribs and steel mesh to form a rigid whole, avoiding localized stress concentration and improving the overall stability of the structure.

[0016] 2. Simplified construction process and shortened construction period: The steel pipe pile group is prefabricated in the factory, requiring only measurement and positioning, pile driving, and grouting operations on site, greatly simplifying the construction process. The retaining wall adopts a lightweight reinforced concrete structure, which is simple to support and has a short curing period, significantly shortening the construction time compared to traditional gravity-type eccentric pressure walls. Traditional eccentric pressure walls require complex formwork support and cast-in-place concrete construction, while the combined anti-lateral displacement pile foundation structure of this shallow buried tunnel eccentric pressure stratum reduces the amount of formwork and labor costs through the integrated pile-wall design.

[0017] 3. Outstanding Economic Efficiency: The lightweight retaining wall design significantly reduces the structure's self-weight, decreases the amount of concrete and steel reinforcement used, and saves material costs. The pile length can be flexibly adjusted according to the ground pressure gradient, avoiding the material waste or insufficient reinforcement problems caused by the fixed thickness of traditional eccentric pressure walls. The pile group layout only requires local drilling and pile driving, preserving the original ground structure to the maximum extent and reducing earthwork excavation, making it particularly suitable for narrow construction sites and complex geological environments.

[0018] 4. Improved Structural Reliability and Durability: The grouting reinforcement zone and the steel pipe piles work together to form a composite load-bearing system, significantly improving the structure's fatigue resistance and long-term service stability. The grout fills the voids in the soil around the piles, not only enhancing soil density and shear strength but also preventing settlement caused by ground disturbance during construction. The rigid connection system, through pile-wall integration, achieves a continuous load transfer path, effectively eliminating localized stress concentration between the traditional eccentrically loaded wall and tunnel lining, and avoiding problems such as lining cracking or joint leakage.

[0019] 5. High adaptability and wide applicability: The length of the steel pipe piles can be flexibly adjusted according to the thickness of the soft soil layer and the depth of the bearing layer to meet the needs of different soil pressure distributions. The quincunx pile group arrangement can flexibly cope with complex terrain and asymmetric load characteristics of biased strata, and has strong geological adaptability. This combined anti-lateral displacement pile foundation structure for shallow buried tunnels in biased strata is particularly suitable for construction environments with narrow terrain or adjacent to existing structures, solving the problem of traditional biased walls occupying a large amount of excavation space.

[0020] 6. Environmental protection and sustainable development: The formation of the grouting reinforcement zone avoids excessive disturbance to the surrounding strata during construction, protects the original stratum structure, reduces earthwork excavation and material waste, and reduces the environmental impact of construction, thus having good ecological benefits. Attached Figure Description

[0021] Figure 1 A schematic diagram of the overall layout of the combined anti-lateral displacement pile foundation structure for shallow-buried tunnels with biased soil strata;

[0022] Figure 2 This is a schematic diagram of the plan layout of the steel pipe pile group;

[0023] Figure 3 This is a structural diagram of each drilled steel pipe in the steel pipe pile group;

[0024] Figure 4 A schematic diagram of the grouting reinforcement zone of a combined anti-lateral displacement pile foundation structure for a shallow-buried tunnel with biased soil strata;

[0025] In the diagram, 1—tunnel, 2—retaining wall, 3—steel pipe pile group, 4—drilled steel pipe, 5—soft soil layer;

[0026] 41—Bearing layer anchorage section; 42—Embedded retaining wall depth section; 43—Grouting hole; 44—Flange; 45—Grouting valve; 46—Annular stiffening rib; 47—Conical pile head; 48—Grouting reinforcement zone. Detailed Implementation

[0027] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0028] To address the limitations of traditional support technologies in dealing with biased soil layers, such as construction constraints, stress concentration, poor adaptability, and high costs, this embodiment provides a combined anti-lateral displacement pile foundation structure for shallow-buried tunnels in biased soil layers. This structure significantly enhances lateral displacement resistance through pile-wall synergy, suppresses asymmetric deformation of weak soil layers, simplifies construction processes, shortens the construction period, and reduces project costs.

[0029] Specifically, such as Figure 1 As shown, the combined anti-lateral displacement pile foundation structure of the shallow-buried tunnel under biased strata includes a retaining wall 2 located on one side of the outside of tunnel 1. The retaining wall 2 is fixed in position by a group of steel pipe piles 3. The retaining wall 2 is a lightweight reinforced concrete structure with a trapezoidal cross-section, specifically: bottom width: 4~5m, top width: 0.6~1.0m, and height: 3~4m. The longitudinal length of the retaining wall 2 is determined according to the length of the shallow-buried biased section at the entrance of tunnel 1. The bottom of the retaining wall 2 is rigidly connected to the above-ground portion of each drilled steel pipe 4 of the steel pipe pile group 3.

[0030] like Figure 1 and Figure 2 As shown, the steel pipe pile group 3 in this embodiment includes three rows of drilled steel pipes 4 arranged vertically along the bias side of tunnel 1. The pile group is arranged in a staggered, quincunx pattern, with a pile spacing of 2.5 to 3.5 times the diameter of the drilled steel pipe 4 to ensure the pile group shares the load. The structure of each drilled steel pipe 4 is as follows:

[0031] like Figure 3 As shown, the drilled steel pipe 4 is made of Q345 seamless steel pipe with an outer diameter D of 0.2~0.4m and a wall thickness t of 12~20mm. The pile length L of the drilled steel pipe 4 is L=H+ΔL1+ΔL2; where H is the thickness of the soft soil layer 5; ΔL1 is the length of the lower bearing layer anchorage section 41 of the drilled steel pipe 4, ΔL1≥2.0m; ΔL2 is the length of the upper embedded retaining wall depth section 42 of the drilled steel pipe 4; the pile length L of the drilled steel pipe 4 can be adjusted according to the ground pressure gradient.

[0032] like Figure 3 As shown, in this embodiment, a number of grouting holes 43 are arranged axially in a staggered quincunx pattern on the bearing layer anchorage section 41 of the perforated steel pipe. The longitudinal spacing S between the grouting holes 43 is 3D~4D, where D is the outer diameter of the steel pipe. The grouting holes 43 are arranged circumferentially at 60° staggered intervals, and the diameter d of each grouting hole 43 is 25~30mm.

[0033] like Figure 3 As shown, the embedded depth section 42 of the drilled steel pipe 4 in the retaining wall is a 1.5~2m non-grouting section, which serves as the anchoring zone for each drilled steel pipe 4. A flange 44 is provided at the top of the embedded depth section 42 of the drilled steel pipe 4, and four grouting valves 45 are installed through the flange 44. Grouting pipelines can be connected through the grouting valves 45 to inject high-pressure grout into each drilled steel pipe 4. After the drilled steel pipe 4 is filled with grout, as... Figure 4 As shown, the grout overflows through the grouting hole 43 to fill the voids in the soil around the pile, forming a grouting reinforcement zone 48 below the retaining wall 2, which enhances the soil density and shear strength. The grouting reinforcement zone 48 works together with the steel pipe pile to form a composite bearing system, which significantly improves the overall lateral displacement resistance of the structure.

[0034] Furthermore, considering the rigidity of the connection between the embedded depth section 42 of each drilled steel pipe 4 and the retaining wall 2, such as Figure 3 As shown, in this embodiment, an annular stiffening rib 46 is provided at the connection between the embedded depth section 42 of the drilled steel pipe 4 and the anchoring section 41 of the bearing layer. The annular stiffening rib 46 is fitted onto the drilled steel pipe 4 and its position relative to the drilled steel pipe 4 is fixed by welding. The function of the annular stiffening rib 46 is that after the embedded depth section 42 of each drilled steel pipe 4 is inserted into the retaining wall 2, the annular stiffening rib 46 can be welded to the bottom reinforcing mesh of the retaining wall 2 to form a rigid whole, thereby enhancing the connection rigidity between each drilled steel pipe 4 and the retaining wall 2, forming a rigid whole of the pile-wall connection structure.

[0035] In addition, such as Figure 3 As shown, in this embodiment, the bottom of the bearing layer anchorage section 41 of each perforated steel pipe is also set as a conical pile head 47, with an angle of 60~75°, to facilitate pile driving construction.

[0036] The construction of the combined anti-lateral displacement pile foundation structure based on the aforementioned shallow-buried tunnel biased strata is as follows:

[0037] First, prefabricated drilled steel pipes 4 are installed in the factory. Grouting holes 43 are arranged on the anchorage section 41 of the bearing layer according to the design, and a non-perforated embedment depth section 42 for the retaining wall is reserved. The pile ends are tapered, and a ring-shaped stiffening rib 46 is welded to the top end of the pile. Then, measurement and positioning are performed for pile driving. Measurements are made according to the predetermined positions to determine the penetration location of the steel pipe piles, with an error ≤5cm. A hydraulic vibratory hammer is used for pile driving, ensuring a verticality deviation ≤1%, and the pile top penetrates to the preset elevation with an error ≤±3cm. Next, grouting valves 45 are installed on each drilled steel pipe 4 for grouting. After grouting, the grouting range and density are checked to ensure that the grouting reinforcement zone 48 meets the design requirements. Finally, the retaining wall 2 is constructed. A shallow trench is excavated in the pile top area, the retaining wall steel mesh is tied and welded to the ring-shaped stiffening rib 46 at the pile end, and concrete is poured after formwork is erected. After the retaining wall is cured, the soil is backfilled and compacted in layers to form a pile-wall-soil collaborative load-bearing system.

[0038] Based on the aforementioned construction process components, the combined anti-lateral displacement pile foundation structure for shallow-buried tunnels in biased strata utilizes steel pipe pile group 3, which is welded to the bottom steel mesh of retaining wall 2 via annular stiffening ribs 46 at the pile top, forming a rigid whole. Retaining wall 2, as the top connecting component of the pile group, concentrates and transfers the anti-lateral displacement capacity of the pile group to the ground surface. Grouting reinforcement zone 48 not only enhances the bearing capacity of the pile group but also transfers the reinforcement effect to retaining wall 2 through the pile-wall connection structure, forming a complete pile-wall-soil collaborative force system. Throughout the construction process, since the steel pipe pile group 3 is prefabricated in the factory, only measurement, positioning, pile driving, and grouting operations are required on-site, significantly simplifying the construction process. The top retaining wall 2 uses a lightweight reinforced concrete structure, which is simple to form and has a short curing period, significantly shortening the construction time compared to traditional gravity biased walls. The entire construction does not require a large amount of excavation space, making it particularly suitable for construction environments with narrow terrain or adjacent to existing structures.

[0039] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this utility model. Various changes and modifications can be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection of this utility model is defined by the appended claims and their equivalents.

Claims

1. A combined anti-lateral displacement pile foundation structure for shallow-buried tunnels in biased strata, characterized in that: It includes a retaining wall located on one side of the tunnel exterior, which is fixed in position by a group of steel pipe piles; the group of steel pipe piles consists of multiple rows of drilled steel pipes arranged vertically along the biased side of the tunnel, and the piles are arranged in a staggered quincunx pattern; each drilled steel pipe is equipped with a grouting hole, which forms a grouting reinforcement zone below the retaining wall after being inserted into the ground for grouting.

2. The combined anti-lateral displacement pile foundation structure for shallow-buried tunnels in biased strata according to claim 1, characterized in that: The retaining wall is made of lightweight reinforced concrete with a trapezoidal cross-section. The longitudinal length of the retaining wall is the same as the length of the shallow buried bias section at the tunnel entrance. The bottom of the retaining wall is rigidly connected to the part of each drilled steel pipe that is exposed above the ground.

3. The combined anti-lateral displacement pile foundation structure for shallow-buried tunnels in biased strata as described in claim 1, characterized in that: The drilled steel pipe is made of seamless steel pipe and includes a bearing layer anchoring section and an embedded retaining wall depth section. Several grouting holes are arranged axially in a staggered quincunx pattern on the bearing layer anchoring section of the drilled steel pipe, and the grouting holes are arranged circumferentially at 60°. A flange is provided at the top of the embedded retaining wall depth section of the drilled steel pipe, and several grouting valves are installed through the flange.

4. The combined anti-lateral displacement pile foundation structure for shallow-buried tunnels in biased strata according to claim 3, characterized in that: The drilled steel pipe has no grouting holes in the section embedded in the retaining wall. It is provided with an annular stiffening rib at the connection with the anchoring section of the bearing layer. The annular stiffening rib is fitted onto the drilled steel pipe and is welded and fixed to the section embedded in the retaining wall and the steel mesh inside the retaining wall.

5. The combined anti-lateral displacement pile foundation structure for shallow-buried tunnels in biased strata according to claim 3, characterized in that: The bottom of the bearing layer anchorage section of the drilled steel pipe is a conical pile head.

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