Soft foundation reinforcing structure in tunnel

Abstract

The utility model discloses a soft foundation reinforcing structure in a tunnel, which comprises a tunnel primary support and further comprises cast-in-place pile foundations, pile tops of the cast-in-place pile foundations are connected through a longitudinal tie beam and a transverse tie beam, a stress dispersion cushion layer is supported above the longitudinal tie beam and the transverse tie beam, and the tunnel primary support is supported above the stress dispersion cushion layer. The method has the beneficial effects that the overall bearing capacity of the tunnel base is improved, and differential settlement is remarkably reduced; the reinforced concrete cast-in-place piles and the ground tie beams act together to form an integral bridge structure, so that the stability of tunnel construction and operation is ensured; the construction method is simple, high in adaptability and suitable for various complex geological conditions of karst caves.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of tunnel construction, and particularly relates to a soft foundation reinforcement structure in a tunnel. BACKGROUND

[0002] The soft foundation refers to a soil layer with soft soil or high clay content above the underground water level in the tunnel construction process. The soft foundation has characteristics such as low bearing capacity, high compressibility, and large settlement, which seriously affect the construction quality and safety of the tunnel. When the tunnel is built on the soft foundation, insufficient bearing capacity of the foundation will lead to uneven settlement of the tunnel, and even phenomena such as subsidence and collapse, which threaten the safety of the tunnel and its surrounding environment.

[0003] Traditional tunnel soft foundation reinforcement methods, such as simply using pile foundation and grouting method, often have unsatisfactory results when there are uneven settlement, karst cave, and soft soil layer in the tunnel foundation. Although the pile foundation can effectively improve the bearing capacity of the foundation, the bearing capacity of the pile foundation is often insufficient under the conditions of soft foundation and karst cave, and the stress transmission between the pile and the surrounding soil is difficult to be uniform, leading to uneven settlement of the foundation. The grouting method may have settlement or collapse after reinforcement due to the difficulty of uniform distribution of grouting materials and the non-durability of the treatment effect.

[0004] Therefore, there is an urgent need for a new tunnel soft foundation reinforcement structure that can effectively reinforce special geological conditions, improve the bearing capacity of the tunnel foundation, and prevent damage caused by uneven settlement. CONTENT OF THE INVENTION

[0005] The application aims to provide a soft foundation reinforcement structure in a tunnel, which solves the problem of uneven settlement of the tunnel foundation through the overall bridge composite structure of the reinforced concrete cast-in-place pile and the ground tie beam, and improves the overall stability and bearing capacity of the tunnel.

[0006] The reinforcement structure effectively forms a synergistic effect by setting the composite structure of the reinforced concrete cast-in-place pile and the ground tie beam in the soft foundation of the tunnel foundation, simultaneously enhances the bearing capacity and overall stiffness of the tunnel foundation in the longitudinal and transverse directions, and eliminates the problem of uneven settlement. The bridge structure formed by the distributed pile foundation and the ground tie beam jointly resists the deformation of the soft foundation, ensuring the long-term stability of the tunnel structure.

[0007] The application achieves the above-mentioned purpose through the following technical solutions:

[0008] A soft foundation reinforcement structure in a tunnel, comprising a tunnel primary support, further comprising a cast-in-place pile foundation, the pile tops of the cast-in-place pile foundation being connected by longitudinal tie beams and transverse tie beams, stress dispersion pads being provided above the longitudinal tie beams and the transverse tie beams, and the tunnel primary support being provided above the stress dispersion pads.

[0009] Further, the tunnel primary support is internally provided with a tunnel secondary support.

[0010] Further, the tunnel primary support is in the shape of a horseshoe.

[0011] Further, the stress dispersion cushion layer comprises a geogrid layer and a lime-soil cushion layer, the geogrid layer is arranged below the tunnel primary support, the lime-soil cushion layer is arranged below the geogrid layer, and the longitudinal tie beams and the transverse tie beams are arranged below the lime-soil cushion layer.

[0012] Further, the bored pile foundation is arranged in two rows along the longitudinal direction, and the two rows of bored pile foundations are arranged symmetrically on both sides.

[0013] Further, the bored pile foundation is arranged in two rows along the longitudinal direction, and the two rows of bored pile foundations are arranged symmetrically on both sides.

[0014] Further, the bored pile foundation is arranged in two rows along the longitudinal direction, and the two rows of bored pile foundations are arranged symmetrically on both sides.

[0015] Further, the longitudinal tie beams and the transverse tie beams are made of reinforced concrete structures.

[0016] Further, the longitudinal tie beams and the transverse tie beams are made of reinforced concrete structures.

[0017] Further, the longitudinal tie beams and the transverse tie beams are made of reinforced concrete structures.

[0018] The beneficial effects of the present application are as follows:

[0019] 1. The overall bearing capacity of the tunnel foundation is improved, and the uneven settlement is significantly reduced.

[0020] 2. The reinforced concrete bored pile and the ground tie beam jointly form an overall bridge structure, ensuring the stability of the tunnel construction and operation.

[0021] 3. The construction method is simple and has strong adaptability, and is suitable for various karst cave complex geological conditions.

[0022] The aforementioned main scheme of the present application and each further selected scheme thereof can be freely combined to form multiple schemes, all of which are the schemes that can be adopted and claimed by the present application; and the present application can also be freely combined between (each non-conflicting selection) and between other selections. Those skilled in the art can understand that there are many combinations according to the prior art and common knowledge after understanding the present scheme, all of which are the technical schemes to be protected by the present application, and are not listed here. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a front elevation view of the structure of the present application.

[0024] Figure 2 is a side elevation view of the structure of the present application.

[0025] Figure: 1 - initial support of the tunnel, 2 - secondary support of the tunnel, 3 - geogrid layer, 4 - lime-soil cushion layer, 5 - longitudinal tie beam, 6 - transverse tie beam, 7 - cast-in-place pile foundation. DETAILED DESCRIPTION

[0026] The application will be further described below in conjunction with specific embodiments and the accompanying drawings.

[0027] Reference Figure 1 and Figure 2 As shown in FIG. 1, a soft foundation reinforcement structure in a tunnel includes an initial support of the tunnel 1, a secondary support of the tunnel 2, a geogrid layer 3, a lime-soil cushion layer 4, a longitudinal tie beam 5, a transverse tie beam 6, and a cast-in-place pile foundation 7.

[0028] The pile tops of the cast-in-place pile foundation 7 are connected by the longitudinal tie beam 5 and the transverse tie beam 6, and a stress dispersion cushion layer is provided above the longitudinal tie beam 5 and the transverse tie beam 6. The initial support of the tunnel 1 is provided above the stress dispersion cushion layer, and the secondary support of the tunnel 2 is provided inside the initial support of the tunnel 1.

[0029] The stress dispersion cushion layer includes the geogrid layer 3 and the lime-soil cushion layer 4. The geogrid layer 3 is provided below the initial support of the tunnel 1, the lime-soil cushion layer 4 is provided below the geogrid layer 3, and the longitudinal tie beam 5 and the transverse tie beam 6 are provided below the lime-soil cushion layer 4. The initial support of the tunnel 1 and the secondary support of the tunnel 2 are horseshoe-shaped, and the upper end surface of the lime-soil cushion layer 4 is an arc-shaped support surface consistent with the camber of the inverted arch. Preferably, the lime-soil cushion layer 4 has an inverted isosceles trapezoidal structure.

[0030] The cast-in-place pile foundation 7 is arranged in two rows along the longitudinal direction, and the two rows of cast-in-place pile foundations 7 are symmetrically arranged on both sides. The pile top elevation of the cast-in-place pile foundation 7 is flush with the height of the inverted arch bedrock, and the cast-in-place pile foundation 7 is arranged with equal length and height.

[0031] The longitudinal tie beam 5 and the transverse tie beam 6 are of reinforced concrete structure, the cast-in-place pile foundation 7 is of reinforced concrete structure, and the longitudinal tie beam 5, the transverse tie beam 6, and the cast-in-place pile foundation 7 are integrally poured structures.

[0032] The composite structure formed by the reinforced concrete bored pile and the ground tie beam in the tunnel foundation soft ground forms a synergistic effect, which can simultaneously reinforce the soft ground, improve the overall bearing capacity of the tunnel, eliminate the possible uneven settlement, and enhance the overall stiffness of the tunnel foundation. The reinforced concrete bored pile is arranged along the longitudinal direction of the tunnel, and one column is arranged on each side. The top of the pile is flush with the inverted arch bedrock, and the length of the pile is arranged along the length of the tunnel. The ground tie beam is arranged along the longitudinal direction and the transverse direction of the tunnel between the two piles. A cushion layer is arranged on the top of the pile and the ground tie beam, and a layer of geogrid is arranged above the cushion layer. The multi-layer design of the cushion layer and the geogrid effectively disperses the local stress concentration and reduces the influence of uneven settlement of the foundation on the upper structure. The geogrid is sequentially provided with an inverted arch initial support and a secondary lining.

[0033] The bored piles are connected by the longitudinal and transverse steel reinforced concrete ground tie beams to form an overall bridge structure, which collectively resists the uneven settlement of the tunnel foundation. The bored piles are formed by a low-clearance rotary drilling machine, and after the hole is formed, the reinforcement cage is bound and the concrete is poured. The ground tie beam is formed by mechanical excavation, and the pile head of the bored pile is broken to the bottom of the ground tie beam, leaving part of the pile top embedded in the ground tie beam. After the pile head reinforcement and the ground tie beam reinforcement are bound and connected, the composite structure is formed by pouring concrete. With the excavation of the tunnel, the bored piles are first connected transversely to form a transverse ground tie beam, and then the bored piles are connected longitudinally to form a longitudinal ground tie beam.

[0034] The tunnel reinforcement structure and the construction method provided by the application provide an economic, effective and reliable solution for the complex geological conditions of the non-continuous development of the cave area, and provide solid technical support for tunnel engineering.

[0035] Advantages of the application: 1. Improving the foundation bearing capacity to ensure the stability of the tunnel structure.

[0036] Through the combination of the reinforced concrete bored pile and the ground tie beam, the composite reinforcement structure forms an overall bridge system, which uniformly distributes the tunnel load to the stable bedrock or foundation. This design not only effectively solves the problem of weakening of the soft foundation on the bearing capacity of the foundation, but also further enhances the overall structural stiffness through the connection of the longitudinal and transverse ground tie beams, greatly reducing the risk of uneven settlement and structural instability caused by the soft foundation.

[0037] 2. Adapt to complex geological conditions, high safety, significant overall reinforcement effect, and adapt to long-term operation requirements.

[0038] The construction method can fully adapt to complex geological conditions: the cast-in-place pile construction adopts a standardized process (drilling-hole cleaning-steel reinforcement cage hoisting-concrete pouring), ensuring stable quality, and the arrangement of cast-in-place piles can be flexibly adjusted (such as pile diameter, pile spacing and pile length) according to the specific distribution of karst caves; the ground tie beam is formed by excavating and connecting in sections, which not only facilitates construction, but also can be advanced synchronously with tunnel excavation, avoiding process conflicts, and the size of the ground tie beam can be flexibly designed according to the tunnel load and construction site conditions; the double-layer setting of the cushion layer and the geogrid provides higher adaptability, effectively disperses local stress concentration, and at the same time reduces the influence of uneven settlement of the base on the tunnel structure. The entire construction process avoids large-scale disturbance of the foundation, reduces the influence on the stability of the tunnel, and improves the safety of construction. This method adapts to various geological conditions and reduces potential settlement and maintenance costs during long-term operation.

[0039] 3. Economic and sustainable.

[0040] Through optimizing the structural design and construction process, the balance between reinforcement cost and engineering quality is achieved: the compact design of cast-in-place piles and ground tie beams effectively controls the use of construction materials, reducing engineering costs; the application of construction equipment (such as low-clearance rotary drilling machines) reduces construction time, further saving labor and machinery costs; the long-term stability of the reinforcement structure reduces the maintenance frequency and cost during tunnel operation, meeting the engineering construction needs of sustainable development.

[0041] 4. Strong generalizability and wide applicability.

[0042] This reinforcement structure is suitable for various types of tunnel projects, especially in areas with variable foundation conditions. At the same time, this method can also be extended to other similar infrastructure projects, such as soft foundation treatment in urban underground space development, etc., with high technical applicability and market value.

[0043] In summary, the present application not only technically solves the problem of tunnel soft foundation reinforcement, but also exhibits significant advantages in economy, construction efficiency and long-term stability, providing an innovative solution for tunnel engineering and related construction technologies.

[0044] The foregoing basic examples and each further selected example of the present application can be freely combined to form multiple embodiments, all of which are embodiments that can be used and claimed by the present application. In the present application scheme, each selected example can be arbitrarily combined with any basic example and selected example.

[0045] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A soft soil foundation reinforcement structure for tunnels, comprising initial tunnel support (1), characterized in that: It also includes cast-in-place pile foundations (7), the tops of the cast-in-place pile foundations (7) are connected by longitudinal tie beams (5) and transverse tie beams (6), stress dispersion cushions are supported above the longitudinal tie beams (5) and transverse tie beams (6), and tunnel initial support (1) is supported above the stress dispersion cushions.

2. The tunnel soft soil foundation reinforcement structure according to claim 1, characterized in that: The tunnel initial support (1) is provided with a tunnel secondary support (2) inside.

3. The tunnel soft soil foundation reinforcement structure according to claim 1, characterized in that: The initial support (1) of the tunnel is horseshoe-shaped.

4. The tunnel soft soil foundation reinforcement structure according to claim 1 or 3, characterized in that: The stress-dispersing cushion layer includes a geogrid layer (3) and a lime-soil cushion layer (4). The geogrid layer (3) is located below the tunnel initial support (1), and the lime-soil cushion layer (4) is located below the geogrid layer (3). The longitudinal tie beam (5) and the transverse tie beam (6) are located below the lime-soil cushion layer (4).

5. The tunnel soft soil foundation reinforcement structure according to claim 1, characterized in that: The cast-in-place pile foundations (7) are arranged in two rows along the longitudinal direction, with the two rows of cast-in-place pile foundations (7) located on both sides and arranged symmetrically.

6. The tunnel soft soil reinforcement structure according to claim 1 or 5, characterized in that: The top elevation of the cast-in-place pile foundation (7) is level with the height of the inverted arch bedrock.

7. The tunnel soft soil foundation reinforcement structure according to claim 6, characterized in that: The cast-in-place piles (7) are arranged with equal length and height.

8. The tunnel soft soil foundation reinforcement structure according to claim 1, characterized in that: The longitudinal tie beam (5) and the transverse tie beam (6) are reinforced concrete structures.

9. The tunnel soft soil foundation reinforcement structure according to claim 1 or 8, characterized in that: The cast-in-place pile foundation (7) is a reinforced concrete structure.

10. The tunnel soft soil foundation reinforcement structure according to claim 1, characterized in that: The longitudinal tie beam (5), the transverse tie beam (6), and the cast-in-place pile foundation (7) are an integral cast-in-place structure.

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