Precast cushion block continuous beam structure erected in soft soil layer tunnel and construction method

Abstract

The present invention belongs to the technical field of tunnel construction, and particularly relates to a precast cushion beam structure and a construction method thereof erected in a tunnel in soft soil layer, which includes a number of precast concrete cushions connected end to end. The precast concrete cushions include two symmetric concrete cushions, and the two concrete cushions are connected together by a supporting steel member, and a connecting steel plate is fixedly connected above the supporting steel member; a number of locking pipe guiding holes are reserved on the concrete cushions; the outer surface of the concrete cushions is roughened. The precast cushion beam structure of the present invention solves safety problems such as settlement, has remarkable effects, strong operability, and remarkable economic and social benefits.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel construction, and particularly relates to a precast cushion block continuous beam structure erected in a soft soil layer tunnel and a construction method thereof. Background Art

[0002] During the construction of underground spaces such as tunnels, especially in soft soil layer tunnels, since the bearing capacity of the formation fails to meet the design requirements, after the initial support arch of the tunnel is installed, the arch feet rest on the soft soil layer, and the bearing capacity of the arch foot foundation is insufficient. To address the above problems, bricks, stones, wooden boards, steel plates, etc. are commonly used as cushion blocks in conventional construction, and the construction is very irregular, unable to effectively solve the settlement problem. The forces on the arch feet of the upper middle bench and the middle lower bench are unstable, which is the main cause of the instability of the initial support of the tunnel. Especially at the node positions of the arch frames in the upper middle bench, which are the weak points of the force on the initial support of the entire tunnel. Particularly in soft tunnel soil layers, if effective measures are not taken to strengthen these nodes, the tunnel will experience significant settlement and in-tunnel convergence deformation. In severe cases, the deformation of the initial support steel arch frame will intrude into the tunnel space limit. If the deformation cannot be controlled in time, continuous settlement will occur, leading to ground collapse and causing serious consequences. Therefore, how to solve the problem of the bearing capacity of the arch frame feet and increase the structural strength at the connection of the upper middle bench is an urgent problem to be solved. Summary of the Invention

[0003] The invention aims to solve the deficiencies of the prior art and provides a precast cushion block continuous beam structure erected in a soft soil layer tunnel and a construction method thereof.

[0004] The invention is achieved through the following technical solutions:

[0005] A precast cushion block continuous beam structure erected in a soft soil layer tunnel includes a number of precast concrete cushion blocks connected end to end. The precast concrete cushion blocks include two symmetric concrete cushion blocks, which are connected together by a support steel member. A connecting steel plate is fixedly connected above the support steel member, and the connecting steel plate is connected to the steel arch frame by bolts. The lower surface of the support steel member is flush with the lower surface of the concrete cushion block, and the upper surface of the connecting steel plate is flush with the upper surface of the concrete cushion block; the length of the precast concrete cushion block is the same as the designed segmented length of the steel arch frame, and the width is the same as the thickness of the shotcrete for the initial support; a number of lock foot conduit guiding holes are reserved on the concrete cushion block; the outer surface of the concrete cushion block is roughened.

[0006] The two ends of the precast concrete cushion block are respectively provided with a matching concave structure and convex structure, and the precast concrete cushion blocks are inserted together through the concave structure and the convex structure.

[0007] At the connection of the precast concrete cushion blocks, there are obliquely penetrating cushion block connection inclined bolt holes through two adjacent precast concrete cushion blocks, and adjacent precast concrete cushion blocks are fixedly connected together by bolts passing through the cushion block connection inclined bolt holes.

[0008] The length of the precast concrete cushion block is 50 - 60 cm, the width is 30 - 35 cm, and the height is 20 - 25 cm.

[0009] The supporting steel member is an I-beam, and there are two supporting steel members.

[0010] The embedding angle of the locking foot conduit guiding hole is 10 - 30°, and the diameter of the locking foot conduit guiding hole is 50 - 150 mm.

[0011] The above-mentioned precast cushion block continuous beam structure erected in the soft soil layer tunnel has the following construction method steps:

[0012] (1) Process precast concrete cushion blocks according to design requirements;

[0013] (2) Excavate the tunnel, place precast concrete cushion blocks at the arch feet, erect steel arch frames, connect the steel arch frames and precast concrete cushion blocks with bolts, spray initial support concrete, and complete the closure of the heading face;

[0014] (3) Drive locking foot conduits through the locking foot conduit guiding holes of the precast concrete cushion blocks;

[0015] (4) Cycle excavation, repeat steps (2) and (3), connect adjacent precast concrete cushion blocks together to form a precast cushion block continuous beam structure.

[0016] Preferably, in step (4), the cyclic excavation footage is the same as the length of the precast concrete cushion block.

[0017] The beneficial effects of the present invention:

[0018] 1. The precast concrete cushion blocks of the present invention are connected to each other to form a precast cushion block continuous beam structure, which is connected into a precast integral continuous beam, increasing the structural stiffness at the joints of the steel arch frames. Especially at the weak joints of the upper and middle benches, the precast cushion block continuous beam structure is adopted, which can quickly bear force and play a role in strengthening the joints.

[0019] 2. The precast concrete cushion blocks of the present invention are precast in advance and fabricated in a factory, and the quality and strength standards can be effectively controlled. Moreover, the outer surface of the whole structure is roughened, which can be effectively connected with the sprayed concrete.

[0020] 3. The middle of the precast concrete cushion block is connected to the steel arch frame by a connecting steel plate, which can ensure the effective connection between the connecting steel plate and the steel arch frame, and the transmitted force and deformation are consistent, so that the force of the steel arch frame is released and transmitted, thereby effectively releasing the soil pressure borne by the initial support steel arch frame.

[0021] IV. Adopt the precast cushion block continuous beam structure to increase the contact area and improve the bearing capacity of the steel arch. The steel arch exerts force on the entire precast cushion block continuous beam structure through the connecting steel plate. Due to the large contact area between the precast cushion block continuous beam structure and the soil layer, the support area is greatly increased. When the precast concrete cushion block of the present invention is not installed, only the area at the joint plate position of the steel arch is stressed. Generally, the area of the joint plate of the steel arch is about 400 cm 2 , after installing the precast cushion block continuous beam structure of the present invention, the contact area is about 1500 - 2000 cm on average 2 , the contact area is greatly improved, effectively increasing the bearing capacity and reducing the settlement deformation of the steel arch.

[0022] V. By installing the precast concrete cushion block of the present invention, the excavation footage per cycle can be reasonably controlled. Since the precast concrete cushion block is fixed and designed according to the spacing length of the arch, and is prefabricated in the factory in advance, modular installation can effectively control the excavation footage of the tunnel face, and can avoid the phenomenon of disorderly over-excavation.

[0023] VI. The precast concrete cushion block of the present invention is provided with a guide hole for the locking foot catheter. Through the guide hole for the locking foot catheter, two problems existing in the conventional locking foot driving process can be solved: 1. After the tunnel face is excavated, it cannot be closed in time. It is necessary to complete the driving of the locking foot catheter and then close it. The locking foot driving time results in too long exposure time of the tunnel face. If the surrounding rock is poor, it will cause the soil mass at the face to fall off, and in severe cases, it will cause collapse; 2. The driving angle of the locking foot is difficult to control. Because there is no guiding device, the driving angle of the locking foot catheter is difficult to control. Often, due to unreasonable angle setting, the locking foot catheter cannot really play the role of anchoring the steel arch. The present invention solves these problems by providing a guide hole for the locking foot catheter on the precast concrete cushion block. Not only indirectly supports the stability of the steel arch through the precast cushion block continuous beam structure, but also can spray concrete in time to close the tunnel face and stabilize the excavated soil layer after the installation of the steel arch, without conflict with the locking foot driving process. After the tunnel face is closed, the locking foot catheter can be driven through the reserved guide hole for the locking foot catheter. In addition, the driving can follow the designed angle during the later driving, effectively ensuring the reasonable stress of the locking foot catheter and reducing the settlement of the steel arch.

[0024] The present invention has more remarkable effects especially during the construction of tunnels in soft soil layers. Because the bearing capacity of the formation cannot meet the design requirements, after the installation of the arch of the initial support of the tunnel, the arch feet bear on the soft soil layer, and the bearing capacity of the arch foot foundation is insufficient. And the padding method in the conventional construction is not standardized, often causing safety problems such as settlement. The steps of the present invention are simple, with remarkable effects, strong operability, saving construction space, and having remarkable economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the structural schematic diagram of the present invention.

[0026] In the figure, 1 is a precast concrete cushion block, 2 is a concrete cushion block, 3 is a supporting steel member, 4 is a connecting steel plate, 5 is a guide hole for the foot-locking conduit, 6 is a concave structure, 7 is a convex structure, 8 is an inclined bolt hole for connecting cushion blocks, and 9 is a bolt hole for connecting the arch frame. Specific embodiments

[0027] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments, and any equivalent transformation based on the technical solution of this application falls within the protection scope of the present invention.

[0028] The precast cushion block connecting beam structure of the present invention is composed of a number of precast concrete cushion blocks 1 connected end to end. The precast concrete cushion block 1 is connected to the joint plate of the steel arch frame above by bolts. There are various ways to connect adjacent precast concrete cushion blocks 1, and the present invention does not limit this. As a preferred solution of this embodiment, in this embodiment, matching concave structures 6 and convex structures 7 are respectively designed at both ends of the precast concrete cushion block 1. The convex structure 7 can be inserted into the concave structure 6, and adjacent precast concrete cushion blocks 1 are plugged together through the concave structure 6 and the convex structure 7. To ensure firm connection, an inclined bolt hole 8 for connecting cushion blocks that obliquely penetrates two adjacent precast concrete cushion blocks 1 is also provided at the connection of the precast concrete cushion blocks 1. As shown in the appendix Figure 1 As shown, bolts pass through the inclined bolt hole 8 for connecting cushion blocks to further fixedly connect adjacent precast concrete cushion blocks 1 together.

[0029] The precast concrete cushion block 1 of the present invention is prefabricated in a factory in advance before construction and customized according to design requirements. The sectional length is designed according to the erection spacing of the steel arch frame. The erection spacing of the steel arch frame in the soft soil layer section is generally 50 - 60 cm. Therefore, the designed length of the precast concrete cushion block 1 of the present invention is also 50 - 60 cm, and the width is the designed thickness of the shotcrete for the initial support, generally 30 - 35 cm. In this way, the precast concrete cushion block 1 is just covered after the shotcrete for the initial support, and the designed height of the precast concrete cushion block 1 is 20 - 25 cm.

[0030] The following is a detailed introduction to the structure of the precast concrete cushion block 1 of this embodiment:

[0031] The precast concrete cushion block 1 of the present invention includes two symmetric concrete cushion blocks 2, and the two concrete cushion blocks 2 are connected together by a support steel member 3. Two I-beams are selected as the support steel member 3. Both ends of the support steel member 3 are fixedly connected to the two concrete cushion blocks 2. There are various connection and fixation methods between the support steel member 3 and the concrete cushion block 2. For example, they can be connected together by integral casting, or bolts can be embedded in the concrete cushion block 2 to connect the support steel member 3 and the concrete cushion block 2 through the embedded bolts, or steel bars can be embedded in the concrete cushion block 2 to weld the support steel member 3 to the concrete cushion block 2, etc. There is no special limitation here.

[0032] A connection steel plate 4 is fixed above the support steel member 3. The connection steel plate 4 and the support steel member 3 can be directly welded together or fixed together by bolts. An arch support connection bolt hole 9 is reserved on the connection steel plate 4, and the connection steel plate 4 is connected to the joint plate of the upper steel arch support through the arch support connection bolt hole 9 and bolts, realizing the connection between the precast concrete cushion block 1 and the steel arch support.

[0033] The lower surface of the above-mentioned support steel member 3 is flush with the lower surface of the concrete cushion block 2, and the upper surface of the connection steel plate 4 is flush with the upper surface of the concrete cushion block 2.

[0034] The outer surfaces of the two concrete cushion blocks 2 of the present invention are roughened, so that they can be well combined with the concrete sprayed in the initial support.

[0035] A number of locking foot conduit guiding holes 5 are reserved on the concrete cushion block 2. The locking foot conduit guiding holes 5 correspond to the positions where the locking foot conduits are driven. The embedding angle of the locking foot conduit guiding holes 5 is 10 - 30°, and the diameter is 50 - 150 mm.

[0036] Applying the precast concrete cushion block 1 of the present invention in tunnel excavation, adjacent precast concrete cushion blocks 1 are connected to form a precast cushion block continuous beam structure. The following is an example to illustrate the construction method of erecting a precast cushion block continuous beam structure in a soft soil layer tunnel, including the following steps:

[0037] (1) Process the above-mentioned precast concrete cushion block 1 according to the design requirements for factory production. The length of the produced precast concrete cushion block 1 is 50 - 60 cm, the width is 30 - 35 cm, and the height is 20 cm - 25 cm. The support steel member 3 uses two I-beams with a length of 30 cm. The support steel member 3 is provided with arch support connection bolt holes 9, and the precast concrete cushion block 1 is provided with locking foot conduit guiding holes 5.

[0038] (2) Excavate the upper bench of the tunnel. After excavation, clean the excavation surface, place the precast concrete cushion block 1 at the arch foot, erect the steel arch support, connect the steel arch support and the precast concrete cushion block 1 by bolts, and spray the initial support concrete to complete the closure of the heading face.

[0039] (3) Driving the foot-locking ducts through the foot-locking duct guiding holes 5 of the precast concrete pads 1.

[0040] (4) Conducting the next excavation cycle and repeating steps (2) and (3). The adjacent precast concrete pads 1 are connected together to form a precast pad continuous beam structure.

[0041] (5) Conducting the upper bench cyclic construction. The excavation footage of each cycle is the same as the length of the precast concrete pad 1. After driving a certain footage, the middle bench is excavated. Precast concrete pads 1 are placed at the arch feet, and steel arch frames are erected. The steel arch frames of the middle bench are connected to the precast concrete pads 1. Shotcreting the initial support concrete to complete the face closure. Conducting the middle bench cyclic construction. The adjacent precast concrete pads 1 are connected together to form a precast pad continuous beam structure. Finally, the excavation of the upper and middle benches is completed.

[0042] The above-described embodiments are only one of the more preferred specific embodiments of the present invention. Ordinary changes and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. A precast cushion block continuous beam structure erected in a tunnel in soft soil layer, characterized in that: It includes a number of precast concrete cushion blocks (1) connected end to end. The precast concrete cushion block (1) includes two symmetrical concrete cushion blocks (2), and the two concrete cushion blocks (2) are connected together by a supporting steel member (3). A connecting steel plate (4) is fixedly connected above the supporting steel member (3), and the connecting steel plate (4) is connected to the steel arch by bolts. The lower surface of the supporting steel member (3) is flush with the lower surface of the concrete cushion block (2), and the upper surface of the connecting steel plate (4) is flush with the upper surface of the concrete cushion block (2); the length of the precast concrete cushion block (1) is the same as the designed segmented length of the steel arch, and the width is the same as the thickness of the shotcrete for the primary support; a number of guide holes (5) for the locking feet conduits are reserved on the concrete cushion block (2); the outer surface of the concrete cushion block (2) is roughened; at the connection of the precast concrete cushion blocks (1), there are inclined bolt holes (8) for connecting the cushion blocks that obliquely penetrate two adjacent precast concrete cushion blocks (1), and adjacent precast concrete cushion blocks (1) are fixedly connected together by bolts passing through the inclined bolt holes (8) for connecting the cushion blocks; the length of the precast concrete cushion block (1) is 50 - 60 cm, the width is 30 - 35 cm, and the height is 20 - 25 cm; concave structures (6) and convex structures (7) are respectively provided at both ends of the precast concrete cushion block (1), and the precast concrete cushion blocks (1) are plugged together through the concave structures (6) and the convex structures (7).

2. The precast cushion block continuous beam structure erected in a soft soil layer tunnel according to claim 1, characterized in that: The supporting steel member (3) is an I-beam, and there are two supporting steel members (3).

3. The precast spacer continuous beam structure erected in a soft soil layer tunnel according to claim 1, wherein: The embedding angle of the guide hole (5) for the locking feet conduit is 10 - 30°, and the diameter of the guide hole (5) for the locking feet conduit is 50 - 150 mm.

4. The precast cushion block continuous beam structure erected in a soft soil layer tunnel according to any one of claims 1 - 3, and its construction method includes the following steps: (I) Process the precast concrete cushion block (1) according to the design requirements; (II) Excavate the tunnel, place the precast concrete cushion block (1) at the arch foot, erect the steel arch, connect the steel arch and the precast concrete cushion block (1) by bolts, and spray the primary support concrete to complete the closure of the heading face; (III) Drive the locking feet conduit through the guide hole (5) for the locking feet conduit of the precast concrete cushion block (1); (IV) Cycle excavation, repeat steps (II) and (III), and connect adjacent precast concrete cushion blocks (1) together to form a precast cushion block continuous beam structure.

5. The construction method of the precast cushion block continuous beam structure erected in a soft soil layer tunnel according to claim 4, characterized in that: In the step (IV), the excavation footage of the cycle excavation is the same as the length of the precast concrete cushion block (1).

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