Foundation pit supporting construction method capable of penetrating through bridge bottom peripheral space limitation

Abstract

The invention relates to the technical field of foundation pit supporting, in particular to a foundation pit supporting construction method for a limited space penetrating through the periphery of the bottom of a bridge, foundation pit supporting is conducted on a building penetrating through the bottom of the bridge through the method, and the problem that a low-clearance and small-permissible-disturbance-deformation bridge lower area supporting structure is difficult to construct can be effectively solved. The stability and safety of the supporting structure are guaranteed, and the surrounding existing structures can be greatly prevented from being damaged.

Description

Technical Field

[0001] The invention relates to the technical field of foundation pit support, in particular to a foundation pit support construction method that passes through a limited peripheral space around a bottom of a bridge. Background Art

[0002] For foundation pit support construction, the traditional construction method is generally a single form of natural slope, support piles plus anchor cables or internal support. However, for foundation pit support construction in some sensitive environments with limited surrounding space, such as: building construction crossing the bottom of a bridge, it is necessary to consider the existing bridge construction around it during construction, which makes it impossible to use simple support and construction forms. Therefore, a foundation pit support construction method that crosses the limited surrounding space at the bottom of a bridge is proposed. Summary of the invention

[0003] The present invention aims to solve the above-mentioned problem, thereby providing a foundation pit support construction method that passes through the limited space around the bottom of a bridge.

[0004] The present invention solves the above-mentioned problem by adopting the following technical solution: A foundation pit support construction method for crossing a limited space around the bottom of a bridge is carried out in the following steps: S1: First, grouting reinforcement is carried out under the bridge cap and the surrounding soil adjacent to the support pile construction area; holes are drilled and grouting pipes are installed in the soil around the bridge cap. Then, the segmented skip-hole grouting process is used to inject cement and water glass mixed slurry into the drill hole. The mixed slurry diffuses in the drill hole to the surrounding soil to increase the anti-disturbance property of the soil; S2: Excavate in sections on both sides of the bridge piers below the bridge deck; excavate the side of the bridge piers away from the support pile construction area with slope; S3: Support pile construction is carried out in the support pile construction area. The support piles close to the bridge pile side are close to the grouting reinforcement soil. During the support pile construction, the support pile steel cage needs to be made in sections, hoisted section by section, and then the two adjacent sections are welded into a whole at the hole mouth; S4: After the support piles on both sides of the bridge are constructed, a concrete retaining wall is constructed on the upper part of the support piles. The top elevation of the concrete retaining wall is the same as the top elevation of the bridge pedestal, and steel bars are thrown inwards; S5: After the construction of the concrete retaining wall is completed, the previously excavated area behind the concrete retaining wall is filled with plain concrete; S6: Construct the internal support beams and the new underground structural raft slab according to conventional construction methods.

[0005] Furthermore, in S1, the grouting pipe is made of seamless steel pipe, and plum blossom-shaped grouting holes are reserved in the pipe wall. During the grouting process, the grouting pressure is applied in stages, and the ratio of the mixed liquid slurry is cement: water glass = 1:0.3-0.5.

[0006] Furthermore, in S2, the slope surface is reinforced by spray anchoring, dowel bars are inserted, and drainage holes are reserved to enhance the integrity of the slope surface and improve the shear strength.

[0007] Furthermore, in S3, the spacing between the support piles is 1.2-1.5 times the pile diameter, and the depth of the pile body embedded in the bearing layer is ≥2m, ensuring the supporting stability of the support piles.

[0008] Furthermore, in S4, a mortise and tenon connection groove is set between the concrete retaining wall and the supporting piles, the thrown-out steel bars are made of HRB400 grade threaded steel bars, and the steel bar lap length is ≥35d; so that the connection between the concrete retaining wall and the supporting piles is more firm and can bear the force synergistically.

[0009] Furthermore, the deformation rate of the bridge structure is monitored in real time throughout the construction process. When the data exceeds the limit, grouting reinforcement is immediately started, and construction is continued after re-testing is qualified; the deformation rate of the bridge structure is monitored in real time to prevent damage to the existing bridge.

[0010] Compared with the prior art, the present invention adopting the above technical solution has the following outstanding features: The method described in the present invention can effectively solve the problem of difficult construction of support structures in the lower area of ​​bridges with low clearance and small allowable disturbance deformation. It not only ensures the stability and safety of the support structure, but also greatly ensures that the surrounding existing structures are not damaged, thereby ensuring construction efficiency and reducing construction costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a schematic diagram of the main structure of an embodiment of the present invention; Markings in the figure are: dowel bar 1, drainage hole 2, slope surface 3, bridge deck 4, bridge pier 5, bridge abutment 6, bridge piles 7, plain concrete 8, concrete retaining wall 9, side wall of new underground structure 10, grouting reinforced soil 11, supporting piles 12, raft slab of new underground structure 13, and inner support beam 14. DETAILED DESCRIPTION

[0012] The present invention will be further described below in conjunction with embodiments, the purpose of which is only to provide a better understanding of the content of the present invention. Therefore, the examples given do not limit the protection scope of the present invention.

[0013] See also Figure 1 , a foundation pit support construction method that passes through the limited space around the bottom of the bridge, is carried out in the following steps: S1: First, grouting reinforcement is performed on the soil below and around the bridge pedestal 6 adjacent to the construction area of ​​the support piles 12; holes are drilled and grouting pipes are installed on the soil around the bridge pedestal 6, and then, a segmented skip-hole grouting process is used to inject a cement-water glass mixed slurry into the drill hole, and the mixed slurry diffuses in the drill hole to the surrounding soil, thereby increasing the soil's anti-disturbance ability.

[0014] S2: Excavate in sections on both sides of the bridge pier 5 below the bridge deck 4; excavate the side of the bridge pier 5 away from the construction area of ​​the supporting piles 12 by slope reduction.

[0015] S3: The support piles 12 are constructed in the construction area, and the support piles 12 on the side close to the bridge piles 7 are close to the grouting reinforcement soil 11; when the support piles 12 are constructed, the support pile steel cage needs to be manufactured in sections, hoisted section by section, and then the two adjacent sections are welded as a whole at the hole mouth; solving the problem of limited net height can speed up the construction speed of the support piles 12.

[0016] S4: The construction of the supporting piles 12 on both sides of the bridge is completed, and the concrete retaining wall 9 is constructed on the upper part of the supporting piles 12. The top elevation of the concrete retaining wall 9 is the same as the top elevation of the bridge cap 6, and steel bars are thrown inward.

[0017] S5: After the construction of the concrete retaining wall 9 is completed, the previously excavated area behind the concrete retaining wall 9 is filled with plain concrete 8; the plain concrete 8 adopts C20 slightly expansive concrete, the layered pouring thickness is ≤500mm, the interval time between layers is ≤2h, and the surface is covered with geotextile for moisture retention maintenance for ≥7 days. During the maintenance period, the displacement of the retaining wall is monitored to be ≤3mm.

[0018] S6: The inner support beam 14 and the newly constructed underground structure raft 13 are constructed in accordance with conventional construction methods; the top height of the newly constructed underground structure side wall 10 is higher than the connection gap between the concrete retaining wall 9 and the support piles 12 .

[0019] In S1, the grouting pipe is made of seamless steel pipe (diameter 25-32mm), and plum blossom-shaped grouting holes (aperture 6-8mm, spacing 200-300mm) are reserved on the pipe wall. During the grouting process, the grouting pressure is applied in stages, with an initial pressure of 0.3MPa and gradually increased to 0.5MPa. The slurry ratio is cement: water glass = 1:0.3-0.5 (water-cement ratio 0.8-1.0).

[0020] In S2, the slope surface 3 is reinforced by spray anchoring, the dowel bar 1 is inserted, and the drainage hole 2 is reserved to enhance the integrity of the slope surface and improve the shear strength.

[0021] In S3, the spacing between the 12 supporting piles is 1.2-1.5 times the pile diameter, and the depth of the pile body embedded in the bearing layer is ≥2m, ensuring the supporting stability of the supporting piles.

[0022] In S4, a mortise and tenon connection groove (groove depth ≥ 100 mm) is set between the concrete retaining wall 9 and the supporting pile 12, the thrown-out steel bars use HRB400 grade threaded steel bars (diameter ≥ 20 mm), and the steel bar lap length is ≥ 35d (d is the steel bar diameter); this makes the connection between the concrete retaining wall 9 and the supporting pile 12 more firm and able to bear force synergistically.

[0023] The deformation rate of the bridge structure is monitored in real time throughout the construction process. When the data exceeds the limit, grouting reinforcement is immediately started, and construction is continued after re-testing is qualified; the deformation rate of the bridge structure is monitored in real time to prevent damage to the existing bridge.

[0024] The method described in the present invention can effectively solve the problem of difficult construction of support structures in the lower area of ​​bridges with low clearance and small allowable disturbance deformation. It not only ensures the stability and safety of the support structure, but also greatly ensures that the surrounding existing structures are not damaged.

[0025] The above description is only a preferred feasible embodiment of the present invention, and does not limit the scope of rights of the present invention. All equivalent changes made using the contents of the present specification and its drawings are included in the scope of rights of the present invention.

Claims

1. A foundation pit support construction method for crossing a limited space around the bottom of a bridge, characterized in that: Follow these steps: S1: First, grouting reinforcement is carried out under the bridge cap and the surrounding soil adjacent to the support pile construction area; holes are drilled and grouting pipes are installed in the soil around the bridge cap. Then, the segmented skip-hole grouting process is used to inject cement and water glass mixed slurry into the drill hole. The mixed slurry diffuses in the drill hole to the surrounding soil to increase the anti-disturbance property of the soil; S2: Excavate in sections on both sides of the bridge piers below the bridge deck; excavate the side of the bridge piers away from the support pile construction area with slope; S3: Support pile construction is carried out in the support pile construction area. The support piles close to the bridge pile side are close to the grouting reinforcement soil. During the support pile construction, the support pile steel cage needs to be made in sections, hoisted section by section, and then the two adjacent sections are welded into a whole at the hole mouth; S4: After the support piles on both sides of the bridge are constructed, a concrete retaining wall is constructed on the upper part of the support piles. The top elevation of the concrete retaining wall is the same as the top elevation of the bridge pedestal, and steel bars are thrown inwards; S5: After the construction of the concrete retaining wall is completed, the previously excavated area behind the concrete retaining wall is filled with plain concrete; S6: Construct the internal support beams and the new underground structural raft slab according to conventional construction methods.

2. The foundation pit support construction method for crossing the limited space around the bottom of a bridge according to claim 1 is characterized in that: In S1, the grouting pipe is made of seamless steel pipe, and plum blossom-shaped grouting holes are reserved on the pipe wall. During the grouting process, the grouting pressure is applied in stages, and the ratio of the mixed liquid slurry is cement: water glass = 1:0.3-0.

5.

3. The foundation pit support construction method for crossing the limited space around the bottom of a bridge according to claim 1 is characterized in that: In S2, the slope surface is reinforced by spraying anchors, inserting rebars, and reserving drainage holes.

4. The foundation pit support construction method for crossing the limited space around the bottom of a bridge according to claim 1 is characterized in that: In S3, the spacing between support piles is 1.2-1.5 times the pile diameter, and the depth of the pile body embedded in the bearing layer is ≥2m.

5. The foundation pit support construction method for crossing the limited space around the bottom of a bridge according to claim 1 is characterized in that: In S4, a mortise and tenon joint groove is set between the concrete retaining wall and the supporting piles, and the thrown-out steel bars are made of HRB400 grade threaded steel bars, and the lap length of the steel bars is ≥35d.

6. The foundation pit support construction method for crossing the limited space around the bottom of a bridge according to claim 1 is characterized in that: The deformation rate of the bridge structure is monitored in real time throughout the construction process. When the data exceeds the limit, grouting reinforcement is immediately started, and construction continues after re-testing is qualified.

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