A method for reinforcing a socketed foundation

Abstract

The application discloses a kind of sleeve arch foundation reinforcing method, including the following construction steps: step one, side slope excavation and protection to arch line position, and make Larsen steel sheet pile.Step two, excavate a certain distance downwards, and make inner support to Larsen steel sheet pile range and weld on steel sheet pile;Step three, continue to excavate to the bottom of sleeve arch foundation, insert profile steel reinforcement, and at the same time, make small catheter grouting reinforcement to sleeve arch foundation;Step four, make sleeve arch foundation;Step five, make sleeve arch upper structure;Step six, tunnel into hole, and close initial support of hole section;Step seven, remove Larsen steel sheet pile outside sleeve arch foundation range.The application can effectively reduce the height of side slope excavation, enhance the bearing capacity of sleeve arch foundation, avoid sleeve arch deformation cracking failure, reduce the risk of side slope instability, and achieve the goal of safe and efficient hole entry.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel construction, and more particularly to a method for reinforcing a sleeve arch foundation. Background Art

[0002] In recent years, with my country's goal of becoming a strong transportation nation, tunnel construction has reached a fever pitch. The number of tunnels built in soft rock is increasing, and the construction of casing arches is unavoidable during tunnel entry. Excessive excavation heights and steep slopes on the side slopes can easily lead to side slope instability and landslides. Furthermore, the insufficient bearing capacity of the casing arch foundations can cause the casing arches to sink, deform, crack, and fail, further contributing to side slope instability and significant losses to construction projects. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for reinforcing a sleeve arch foundation, which can effectively reduce the excavation height of the side slope for weak surrounding rock, enhance the bearing capacity of the sleeve arch foundation, avoid deformation, cracking and failure of the sleeve arch, reduce the risk of instability of the side slope, and achieve the goal of safe and efficient tunneling.

[0004] The technical solution adopted by the present invention to solve this technical problem is: a method for reinforcing a sleeve arch foundation, comprising the following construction steps:

[0005] Step 1: Excavate the slope and protect it to the arch line, and install Larsen steel sheet piles.

[0006] Step 2: Excavate downwards for a certain distance, apply internal support to the Larsen steel sheet pile area and weld it to the steel sheet pile;

[0007] Step 3: Continue excavating to the bottom of the sleeve arch foundation, insert steel reinforcement, and simultaneously perform small conduit grouting reinforcement on the sleeve arch base;

[0008] Step 4: Construct the arch foundation;

[0009] Step 5: construct the arch superstructure;

[0010] Step 6: Enter the tunnel and close the initial support of the entrance section;

[0011] Step 7: Remove the Larsen steel sheet piles outside the arch foundation range.

[0012] Preferably, step one is as follows: the side slope excavation slope is 1:1.0, the back slope excavation slope is 1:0.25, protection adopts φ42mm×4mm small conduit with a length of 3m, a spacing of 2m×2m, and a plum blossom shape arrangement, the slope surface is hung with φ8mm steel mesh and sprayed with C25 concrete support with a thickness of 10cm, and the Larsen steel sheet piles are installed with a length of 9m, a spacing of 40cm, and are installed on three sides.

[0013] Preferably, step 2 specifically includes: after constructing the Larsen steel sheet piles, continue to excavate downward for a certain distance, then construct internal supports within the range of the Larsen steel sheet piles and weld them to the steel sheet piles.

[0014] Preferably, step three is as follows: after continuing to excavate to the bottom of the arch foundation, steel and small pipes are driven into the arch foundation. The steel is I-18 steel, 6m long, arranged in 3 rows and 2 columns, with a spacing of 50cm×50cm. The small pipe is ×4mm small tubes, 6m in length, arranged in 4 rows and 3 columns with a spacing of 50cm×50cm.

[0015] Preferably, in step four, the casing arch foundation has dimensions of 2.4 m in length × 2.0 m in width × 3.2 m in depth, is cast with C35 plain concrete, and a 1.5 m long casing arch is pre-embedded.

[0016] Preferably, in step five, the upper structure of the arch foundation is a 70 cm thick C35 concrete arch.

[0017] The present invention has at least the following beneficial effects:

[0018] The present invention can effectively reduce the excavation height of the side slope of the tunnel surface, and at the same time provide effective support to the foot of the side slope, thereby enhancing the stability of the slope and reducing the risk of instability of the side slope.

[0019] The present invention can effectively improve the bearing capacity of the base of the sleeve arch foundation, increase the strength of the sleeve arch, and avoid problems such as sinking, sliding deformation, cracking and failure of the overall structure of the sleeve arch in the later stage.

[0020] The present invention can reduce the workload during tunnel entry, speed up the construction progress, shorten the construction period of the sleeve arch, and has certain technical advantages and excellent economic efficiency.

[0021] Other advantages, objectives and features of the present invention will be reflected in part from the following description and will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the elevation drawing of the arch foundation reinforcement.

[0023] Figure 2 This is the plan for reinforcing the arch foundation.

[0024] Figure 3 This is the general drawing of Larsen steel sheet pile.

[0025] Figure 4 Diagram of slope tensile cracks.

[0026] Figure 5 Arch displacement diagram.

[0027] Figure 6 Arch foundation reinforcement diagram.

[0028] Figure 7 The completed effect of the arch.

[0029] Description of reference numerals:

[0030] 1-side slope soil, 2-slope support, 3-first small conduit, 4-Larsen steel sheet pile, 5-upper soil of arch foundation part, 6-Larsen steel sheet pile inner support, 7-lower soil of arch foundation part, 8-arch foundation reinforcement 18-section steel, 9-foundation reinforcement small conduit, 10-C35 arch foundation, 11-arch steel support, 12-C35 concrete arch. DETAILED DESCRIPTION

[0031] The present invention is described in detail and completely below with reference to the accompanying drawings. Those skilled in the art will be able to implement the present invention based on this description. Before describing the present invention with reference to the accompanying drawings, it should be noted that the technical solutions and technical features provided in various parts of the present invention, including those described below, may be combined with each other unless they conflict.

[0032] In addition, the embodiments of the present invention described below are generally only part of the embodiments of the present invention, rather than all of the embodiments. Therefore, based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making any creative efforts should fall within the scope of protection of the present invention.

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The specific implementation process is as follows:

[0034] Example 1

[0035] like Figures 1 to 3 As shown, a method for reinforcing a sleeve arch foundation includes the following steps:

[0036] (1) Excavate the side slope soil in level 1 until the arch line is reached. The side slope gradient is controlled at 1:1 and the back slope gradient is controlled at 1:0.25.

[0037] (2) Apply slope support 2, first hang Steel mesh, steel mesh grid 20×20cm, followed by spraying C25 concrete, thickness 10cm.

[0038] (3) The first small conduit 3 is constructed on the slope and grouting is carried out. The specification of the first small conduit is The length is 3m, the spacing is 2m×2m, the arrangement is in plum blossom shape, the slurry water-cement ratio is 1:0.8, and the grouting pressure is 0.5Mpa.

[0039] (4) 4 Larsen steel sheet piles were installed. The length of the steel sheet piles was 9 m, the spacing was 40 cm, and they were installed on three sides and inserted vertically into the soil.

[0040] The model is SP-Ⅳ Larsen steel sheet pile

[0041] (5) Excavate the upper soil 5 of the arch foundation, that is, excavate 50 cm downward.

[0042] (6) Construct the Larsen steel sheet pile inner support 6, i.e., the inner support of Work 18, and weld it together with the Larsen steel sheet pile.

[0043] (7) Continue to excavate the lower soil 7 of the arch foundation part.

[0044] (8) Construction of arch foundation reinforcement 18 steel 8 and foundation reinforcement small pipe 9 ( Small pipes) are all driven vertically downward into the soil. The foundation reinforcement small pipes 9 are arranged in 4 rows and 3 columns with a spacing of 50×50cm. The arch foundation reinforcement 18-shaped steel 8 are arranged in 3 rows and 2 columns with a spacing of 50×50cm. The foundation reinforcement small pipes 9 are injected with single-liquid slurry, with a water-cement ratio of 1:0.8 and a grouting pressure of 0.5Mpa.

[0045] (9) Pour concrete for the C35 arch foundation 10 and embed a section of arch steel support 11. The embedded length of the arch steel support 11 is 1.5 m.

[0046] (10) The upper structure of the arch foundation was cast in molds, and a 70 cm thick C35 concrete arch 12 was constructed. The pipe shed was set up, and the grouting and grouting quality inspection were completed.

[0047] (11) The tunnel is entered and the initial support of the entrance section is closed.

[0048] (12) Remove the Larsen steel sheet piles outside the arch foundation.

[0049] Comparative Example 1

[0050] The entrance section of a certain urban expressway tunnel consists of a cluster of four tunnels with small clearances. This shallow section traverses a long distance through residual slope soil, fully weathered, and sandy, highly weathered granite strata. The soil structure is unstable, the core rock is extremely fragmented, softens upon contact with water, and easily crumbles, making it an extremely soft rock. The tunnel site is rich in groundwater, with the water table higher than the tunnel roof, and the soil has a high natural moisture content. The right auxiliary tunnel serves as the pilot tunnel, and the following construction techniques were used during entry:

[0051] ① Excavate the side slope soil in stages to the bottom elevation of the arch foundation, controlling the slope ratio of the side slope to 1:1 and the slope ratio of the back slope to 1:0.25; ② Apply slope protection, first hang the mesh spraying Steel mesh, steel mesh grid 20×20cm, followed by spraying C25 concrete, thickness 10cm; ③ Support the formwork, cast the arch foundation, and pre-embed a section of arch steel support; ④ After formwork casting, the arch superstructure.

[0052] like Figure 4 、 5 As shown, the above-mentioned conventional method was used for construction, and the construction quality was strictly controlled during the process. However, after the arch was completed, monitoring found that the side slope was still in deformation, and the arch foundation also experienced uneven settlement, with the maximum deformation of 70cm, which seriously affected the construction progress and brought great risks to the project construction.

[0053] Research has found that the main reasons for the deformation of the side slope and the arch are that the surrounding rock is broken and weak, softened by water, has insufficient bearing capacity, the side slope is too large, and there is no effective support at the toe of the slope.

[0054] Later, when constructing the sleeve arch of the right main tunnel, the left main tunnel and the left auxiliary tunnel, the embodiment 1 "A sleeve arch foundation reinforcement method" was adopted. The excavation of the side slope was changed from the original excavation to the bottom elevation of the sleeve arch foundation to the excavation to the arch line, reducing the slope height by 3.2m. It not only effectively reduced the risk of slope instability, but also greatly reduced the amount of excavation. In addition, Larsen steel sheet piles were installed at the slope corners of the side slope to form an effective support for the slope foot. The weak soil layer of the sleeve arch foundation was treated by small-duct grouting in combination with I-18 I-steel. The grouting pressure can compact the soil layer. At the same time, the cement slurry penetrates the soil layer to form a cement-soil stabilizing material, which is then combined with I-18 I-steel to form steel piles, and the bearing capacity of the foundation is effectively improved. After the construction was completed, the side slope was basically in a stable state, and the sleeve arch had no obvious settlement and deformation, with good results (such as Figure 6 、 7 shown).

[0055] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A method for reinforcing a sleeve arch foundation, characterized in that: The construction steps include: Step 1: Excavate and protect the side slope up to the arch line, and install Larsen steel sheet piles. The side slope excavation slope is 1:1.0, and the back slope excavation slope is 1:0.

25. Protection uses φ42mm×4mm small pipes, 3m long, 2m×2m apart, arranged in a plum blossom shape. The slope surface is hung with φ8mm steel mesh and sprayed with C25 concrete support, 10cm thick. Larsen steel sheet piles are installed with a length of 9m and a spacing of 40cm on three sides. Step 2: Excavate downwards for a certain distance, apply internal support to the Larsen steel sheet pile area and weld it to the steel sheet pile; Step 3: After continuing to excavate to the bottom of the sleeve arch foundation, insert steel reinforcement and simultaneously perform small conduit grouting reinforcement on the sleeve arch base; wherein, the steel is I-18 steel, 6m long, arranged in 3 rows and 2 columns, with a spacing of 50cm×50cm; the small conduits are φ42mm×4mm small conduits, 6m long, arranged in 4 rows and 3 columns, with a spacing of 50cm×50cm; Step 4: Construct the arch foundation. The arch foundation has dimensions of 2.4m long, 2.0m wide, and 3.2m deep. It is cast with C35 plain concrete and a 1.5m long arch is embedded in the foundation. Step 5: Construct the upper structure of the arch; the upper structure of the arch foundation is a 70cm thick C35 concrete arch; Step 6: Enter the tunnel and close the initial support of the entrance section; Step 7: Remove the Larsen steel sheet piles outside the arch foundation range.

2. The method for reinforcing a sleeve arch foundation according to claim 1, wherein: The specific steps in step 2 are as follows: after constructing the Larsen steel sheet piles, continue to excavate downward for a certain distance, then construct internal supports within the range of the Larsen steel sheet piles and weld them to the steel sheet piles.

3. The method for reinforcing a sleeve arch foundation according to claim 1, wherein: Step three is as follows: Continue excavating to the bottom of the sleeve arch foundation, and then drive steel sections and small conduits into the sleeve arch foundation.

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