Deep foundation pit bored pile enclosure intrusion boundary reinforcement treatment structure and method

Abstract

The application relates to a deep foundation pit bored pile enclosure intrusion boundary reinforcement treatment structure and method, which comprises: a water-stopping high-pressure rotary jet pile arranged outside the enclosure pile, a support, a bottom plate cushion layer and a hidden beam reinforcing structure used in the upper and lower intrusion boundary areas, and an anchor rod reinforcing structure used in the intrusion boundary soil layer. The method comprises the following specific steps: (1) reinforcing and compensating by additionally arranging high-pressure rotary jet piles outside the offset row piles; (2) after the foundation pit is excavated to the upper support elevation of the intrusion boundary area, the sectional size of the original concrete enclosure purlin and the concrete angle support is reinforced; (3) when the excavation of the bearing platform drop pit is carried out, the intrusion row piles are chipped off while the excavation is carried out; (4) during the chipping-off process, the soil layer anchor rod method is simultaneously used to reinforce the pile foundation in the chipped-off area; and (5) after the excavation is carried out to the bottom of the bearing platform pit, the cushion layer in the area is reinforced, and a concrete waist beam is additionally arranged. The application can be used for solving the situation that the enclosure structure intrudes into the boundary due to various reasons in engineering, greatly reducing the safety hidden danger of the enclosure structure and reducing the subsequent construction cost.

Description

Technical Field

[0001] This invention relates to a deep foundation pit bored cast-in-place pile, and more particularly to a structure and method for reinforcing the boundary of a deep foundation pit bored cast-in-place pile retaining wall. Background Technology

[0002] Currently, many deep foundation pits under construction employ a method of retaining the foundation pit with drilled cast-in-place piles and internal bracing. This type of retaining structure requires high standards in terms of pile positioning, pile construction management, and operational skills. However, during actual construction, due to mechanical, geological, and human factors, retaining piles often encroach on the outer wall boundary of the structure after excavation. In addition, some projects are constrained by the construction site, requiring the main structure to be constructed close to the retaining piles. In such cases, since the outer wall of the basement structure cannot be constructed, the portion of the retaining piles encroaching on the basement structure must be removed to ensure the thickness and integrity of the basement structure's floor slab, foundation, and side walls. However, this significantly reduces the safety factor of the foundation pit retaining structure during construction. In severe cases, it can lead to insufficient bending and shear bearing capacity at the weakened section of the pile foundation in the removed area, excessive deformation, and cracking, potentially resulting in major personnel and safety accidents. Therefore, it is essential to treat the removed portion of the retaining piles. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of the existing technology mentioned above, and to solve the problem that after the foundation pit is excavated, the retaining piles often intrude into the outer wall of the structure. In addition, some projects are constrained by the construction site, and the main structure is constructed close to the retaining piles. In this case, the outer wall of the basement structure cannot be constructed. Therefore, this invention provides a structure and method for reinforcing the retaining piles in deep foundation pits to prevent boundary encroachment. This invention can be used to solve the problem of retaining structure encroachment due to various reasons in engineering projects, greatly reduce the safety hazards of the retaining structure, and reduce subsequent construction costs.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is: a deep foundation pit bored pile retaining wall reinforcement structure, comprising: water-stopping high-pressure jet grouting piles installed on the outside of the retaining piles, a support, bottom slab cushion and hidden beam reinforcement structure above and below the intrusion zone, and an anchor rod reinforcement structure for the soil layer in the intrusion zone.

[0005] A construction method for a deep foundation pit bored pile retaining wall reinforcement structure, the specific steps of which are as follows:

[0006] (2) High-pressure jet grouting piles were driven on the outer side of the offset piles for reinforcement;

[0007] (2) After the foundation pit is excavated to the support elevation of the upper layer of the boundary zone, the cross-sectional dimensions of the original concrete waler and concrete corner brace are strengthened;

[0008] (3) When excavating the foundation pit, the encroaching piles are removed at the same time.

[0009] (4) During the chiseling process, the soil anchor method is used to strengthen the pile foundation in the chiseling area.

[0010] (5) After excavation to the bottom of the foundation pit, the subbase in this area is reinforced, a concrete wainscoting is added, a concrete hidden beam is added in the subbase, and the concrete hidden beam is connected to the retaining structure by rebar anchoring or welding. A steel mesh is arranged in the reinforced subbase area.

[0011] Furthermore, the reinforcement construction of high-pressure jet grouting piles on the outer side of the offset pile requires pilot holes with a pile diameter of 800mm, and the reinforcement range extends from the top ring beam to 4m below the bottom of the pile cap.

[0012] Furthermore, the thickness of the original concrete corner bracing supporting the upper layer of the encroachment area is increased to no less than 300mm;

[0013] Furthermore, after excavating to the bottom of the foundation pit, the subbase in this area is reinforced. Specifically, a 1000mm*800mm concrete lintel beam is added, and a 1000mm*800mm concrete hidden beam is added inside the subbase. The hidden beam is connected to the retaining structure by anchoring or welding. A φ18@250 single-layer bidirectional steel mesh is arranged in the reinforced area of ​​the subbase.

[0014] Furthermore, the anchor rods for the soil anchor method use HRB335 grade φ15mm steel bars, which are arranged starting from the top of the pile removal area, with a vertical spacing of 500mm and arranged in parallel vertically. The anchor rod inclination angle is 20°. The channel steel is connected to the piles on both sides, and the channel steel is No. 10 channel steel. The anchor rods are inserted into the soil layer for no less than 6m. In order to ensure the bending resistance of the pile foundation in this area, the main reinforcement bars in the tension zone of the removed side piles must be retained.

[0015] The beneficial effects of this invention are:

[0016] This invention utilizes external waterstopping, upper and lower supports in the area where the intruding pile foundation is removed, and reinforcement of the support points of the hidden beams in the cushion layer. Combined with the vertical setting of multiple soil layer anchor rods in the weak pile foundation section of the removed area, the structural stress is transformed from a vertically single-span simply supported bending section in the area of ​​the intruding pile foundation to a continuous beam with vertical multi-span support in the area of ​​the intruding pile foundation. Compared with the original simply supported bending section in the large span area, the mid-span bending moment is greatly reduced, and the weakened section can still meet the requirements. At the same time, the deformation of the simply supported pile foundation transformed into a multi-span continuous pile foundation is also greatly reduced.

[0017] This invention effectively addresses the construction problem of safely reinforcing the exterior walls of basement structures that encroach on the boundary, avoiding the traditional situation where the enclosure structure encroaches on the boundary due to various reasons. This reduces safety hazards in subsequent construction, significantly improves construction efficiency, and reduces construction costs. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the plan layout for the reinforcement treatment of the encroachment enclosure;

[0019] Figure 2This is the elevation development diagram of the anchor bolt;

[0020] Figure 3 This is a schematic diagram of the cross-sectional arrangement of anchor bolts used to reinforce the soil layer encroached by the retaining piles;

[0021] Figure 4 This is a schematic diagram of the retained reinforcement bars in the retaining piles. Detailed Implementation

[0022] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments of the Shanghai Pudong Airport foundation pit project. These embodiments are for illustrative purposes only and are not intended to limit the technical solutions described herein. After reading the teachings of this invention, those skilled in the art can make various modifications or equivalent substitutions to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0023] like Figures 1 to 4 As shown, the present invention provides a deep foundation pit bored pile retaining wall boundary reinforcement structure, comprising: a water-stopping high-pressure jet grouting pile 2 installed on the outside of the retaining pile; a support, bottom slab cushion and hidden beam reinforcement structure above and below the boundary zone; and an anchor rod reinforcement structure for the soil layer in the boundary zone.

[0024] like Figures 1 to 4 As shown, the construction method of the present invention, which adopts a deep foundation pit bored pile retaining wall reinforcement structure, includes the following specific steps:

[0025] (1) High-pressure jet grouting piles 2 are added to the outside of the offset pile 1 for reinforcement and strengthening. The pile diameter is 800mm. The reinforcement range is from the top ring beam to 4m below the bottom of the pile cap. The top ring beam construction in this area has been completed. The reinforcement construction requires drilling.

[0026] (2) After the foundation pit is excavated to the general area bottom slab elevation, the original design of 2000mm*2000mm*200mm concrete corner bracing in this area is changed to 4000mm*4000mm*300mm concrete corner bracing 5;

[0027] (3) When excavating the foundation pit, the encroaching piles are removed at the same time.

[0028] (4) During the excavation process, soil anchoring is used to reinforce this area. Anchors 3 are made of HRB335 grade φ15 steel bars, arranged vertically at 500mm intervals, parallel to each other, starting from the top of the pile excavation area. The anchor angle of anchor 3 is 20°. Channel steel 4 is connected to the offset piles 1 on both sides. Channel steel 4 is made of 10# channel steel. Anchors 3 are inserted into the soil layer for no less than 6m. Under the action of anchors 3, as the foundation pit is excavated and the pile foundation is excavated to the offset side, it will be subjected to tensile force. To ensure the bending resistance of the pile foundation in this area, the main reinforcement 7 of the tensile area of ​​the excavated side piles must be retained.

[0029] (5) After excavation to the bottom of the foundation pit, the cushion layer in this area is reinforced and a 1000mm*800mm concrete wainscoting is added. A 1000mm*800mm concrete hidden beam 8 is added in the cushion layer 6. The concrete hidden beam 8 is connected to the retaining structure by rebar anchoring or welding. A φ18@250 single-layer bidirectional steel mesh is arranged in the reinforced area of ​​the cushion layer 6.

Claims

1. A construction method for a deep foundation pit bored pile retaining wall boundary encroachment reinforcement structure, the deep foundation pit bored pile retaining wall boundary encroachment reinforcement structure comprising: High-pressure jet grouting piles for water stoppage are installed on the outside of the retaining piles. The upper and lower parts of the boundary encroachment zone are reinforced with supports, a base slab, and hidden beams. The soil layer in the boundary encroachment zone is reinforced with anchor bolts. The specific steps are as follows: (1) Reinforce the outer side of the offset pile by driving high-pressure jet grouting piles; (2) After the foundation pit is excavated to the support elevation of the upper layer of the boundary zone, the cross-sectional dimensions of the original concrete waler and concrete corner brace are strengthened; (3) When excavating the foundation pit, the encroaching piles should be removed while excavating; (4) During the chiseling process, the soil anchor method is used to strengthen the pile foundation in the chiseling area; (5) After excavation to the bottom of the foundation pit, the subbase in this area is reinforced, a concrete wainscoting is added, a concrete hidden beam is added in the subbase, and the hidden beam is connected to the retaining structure by rebar anchoring or welding. A steel mesh is arranged in the reinforced subbase area.

2. The construction method according to claim 1, characterized in that: For the reinforcement of the outer side of the offset pile row, high-pressure jet grouting piles need to be drilled. The pile diameter is 800mm, and the reinforcement range extends from the top ring beam to 4m below the bottom of the pile cap.

3. The construction method according to claim 1, characterized in that: The thickness of the original concrete corner bracing on the upper layer of the encroachment area shall be increased to no less than 300mm.

4. The construction method according to claim 1, characterized in that: After excavation to the bottom of the foundation pit, the subbase in this area is reinforced. Specifically, a 1000mm*800mm concrete lintel beam is added, and a 1000mm*800mm concrete hidden beam is added inside the subbase. The 1000mm*800mm concrete hidden beam is connected to the retaining structure by anchoring or welding. A φ18@250 single-layer bidirectional steel mesh is arranged in the reinforced area of ​​the subbase.

5. The construction method according to claim 1, characterized in that: For the soil anchoring method, HRB335 grade φ15mm steel bars are used as anchors. They are arranged starting from the top of the pile removal area, with a vertical spacing of 500mm and parallel arrangement. The anchor angle is 20°. The channel steel is connected to the piles on both sides. The channel steel is 10# channel steel. The anchors are inserted into the soil layer for no less than 6m. To ensure the bending resistance of the pile foundation in this area, the main reinforcement bars in the tension zone must be retained for the removed side piles.

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