Open excavation construction isolation reinforcing method adjacent to existing building

Abstract

The invention relates to the technical field of geotechnical engineering and underground construction, in particular to an isolation and reinforcement method for open excavation construction adjacent to an existing structure, which comprises the following steps of: 1) determining the position of an isolation belt: determining a belt-shaped area parallel to the side line of an open excavation area as the isolation belt between the open excavation area planned to be excavated and the existing structure; (2) a composite anchor rod pile group is constructed, specifically, a plurality of composite anchor rod piles are constructed in the isolation belt in the trend of the isolation belt at the center-to-center interval E; the construction of the composite anchor rod pile comprises the steps of drilling, placing a steel bar rod body and performing high-pressure grouting; and (3) forming a continuous reinforcing body through high-pressure grouting, specifically, during high-pressure grouting, the grouting pressure is controlled, and the effective diffusion radius R of grout in a soil body meets the condition that R is larger than or equal to 0.5 * E, so that it is ensured that grouting bodies of the adjacent composite anchor rod piles are in lap joint with one another, and a continuous vertical reinforcing isolation wall is formed.

Description

Technical Field

[0001] This invention relates to the fields of geotechnical engineering and underground construction technology, and in particular to a method for actively controlling deformation, isolating the effects of excavation, and reinforcing the soil around piles during open-cut construction near existing bridges, buildings, and other important structures. Background Technology

[0002] In urban underground space development, excavation of foundation pits or construction of utility tunnels next to existing operating bridges, subway tunnels, and building foundations is a common challenge. Such construction severely disrupts the original stress balance of the soil, causing changes in the lateral earth pressure of adjacent pile foundations, leading to pile displacement, and significantly reducing their lateral friction resistance, directly threatening the safety and normal use of existing structures.

[0003] Existing technologies often use diaphragm walls or large-diameter piles as isolation measures. However, these isolation measures are suitable for deep foundation pit excavation and support measures, but they have many drawbacks. For example, the large equipment required is difficult to deploy in confined spaces such as under bridges, which leads to construction inconvenience; the amount of materials used is large, resulting in high project costs; vibration and mud during trenching or drilling have a significant impact on the surrounding environment and existing structures; and they mainly serve an isolation function, with limited effect on the active reinforcement and improvement of the soil around the piles.

[0004] Therefore, there is an urgent need in this field for a comprehensive solution that integrates active reinforcement, deformation isolation, and spatial adaptability, and is cost-effective and efficient. Summary of the Invention

[0005] The primary objective of this invention is to overcome the shortcomings of the prior art and provide a flexible and reliable open-cut construction method for isolation and reinforcement. This method can actively reinforce the soil around existing structures and form a continuous isolation barrier.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for open-cut construction to isolate and reinforce adjacent existing structures, the method comprising the following steps: 1) Determine the location of the isolation zone: Between the planned open-cut area and existing structures (such as bridge pile foundations), determine a strip-shaped area parallel to the open-cut edge as an isolation zone; 2) Construction of composite anchor pile group: Within the isolation zone, multiple composite anchor piles are constructed along its direction at a center-to-center spacing E; the construction of the composite anchor piles includes drilling, placement of reinforcing bars, and high-pressure grouting; 3) High-pressure grouting forms a continuous reinforced body: During high-pressure grouting, a certain proportion of grout is used and the grouting pressure is controlled so that the effective diffusion radius R of the grout in the soil satisfies: R ≥ 0.5 × E, thereby ensuring that the grout bodies of adjacent composite anchor piles overlap each other to form a continuous vertical reinforced isolation wall. 4) Effect verification and process monitoring: Verify the unconfined compressive strength of the reinforced isolation wall and monitor the existing structure in real time during the subsequent open-cut construction.

[0007] Preferably, in step 2), the diameter F of the composite anchor pile is 150 mm and the center-to-center distance E is 400 mm.

[0008] Preferably, in step 3), the grout is a cement grout with a water-cement mass ratio of 1:0.5, and the grouting pressure is 0.5 MPa to 1 MPa.

[0009] Preferably, in step 3), the high-pressure grouting is achieved through a layered, multiple grouting process.

[0010] Preferably, in step 4), the unconfined compressive strength of the vertically reinforced isolation wall is not less than 0.5 MPa.

[0011] Preferably, in step 2), when the construction space is limited, the steel bar is extended in sections and the joints are connected by flash butt welding.

[0012] The steel bar includes isolation rings, longitudinal steel bars, and positioning support steel bars. Isolation rings are set at intervals along the length of the longitudinal steel bars, and several positioning support steel bars are evenly arranged on the isolation rings perpendicular to the longitudinal steel bars.

[0013] Preferably, the isolation ring is a ring-shaped component formed by threaded steel bars; three longitudinal steel bars are arranged in a triangle, and the isolation ring is located inside the longitudinal steel bars arranged in the triangle; three positioning support steel bars are evenly arranged on an isolation ring, spaced apart from the longitudinal steel bars.

[0014] The present invention provides a pile group consisting of multiple composite anchor piles between an open-cut area and existing structures; each composite anchor pile includes a borehole, a steel rod installed in the borehole, and a grout body formed by high-pressure grouting. The center-to-center distance between two adjacent composite anchor piles is E. The grout diffusion radius R formed by the grout in the soil satisfies: R ≥ 0.5 × E, so that the grout of all composite anchor piles overlaps with each other in the isolation zone, forming an integral, vertical reinforced isolation wall.

[0015] The composite anchor pile has a diameter F of 150mm and a center-to-center spacing E of 400mm. The radius r of the composite anchor pile is defined as the distance from the center of the reinforcing bar to the end of the positioning support reinforcing bar. The diameter of the composite anchor pile is 2r.

[0016] The isolation and reinforcement structure formed by this invention has the dual functions of soil improvement and deformation isolation.

[0017] Compared with the prior art, the present invention has the following technical advantages: This invention is the first to propose the core idea of ​​actively "constructing" a continuous isolation wall by controlling the quantitative relationship between "grout diffusion radius (R)" and "pile center distance (E)" (R ≥ 0.5E). This transcends the traditional passive thinking of relying on the pile body itself for isolation and represents a conceptual leap from "passive support" to "actively constructing a reinforced zone".

[0018] Synergistic effect of the technology: By combining "small-diameter, high-density pile groups" with "high-pressure grouting with specific parameters", a synergistic effect of "1+1>2" is generated. This method not only forms a physical isolation barrier, but more importantly, it substantially improves the soil around the piles, fundamentally achieving the core engineering goal of "maintaining the existing side friction resistance of the pile foundation", which is difficult to achieve with traditional isolation measures.

[0019] Significant economic benefits and adaptability: Replacing large-diameter support piles or diaphragm walls with small-diameter anchor piles significantly reduces material costs and equipment requirements. Its modular and linear construction characteristics make it unparalleled in its adaptability to narrow spaces such as under bridges and along utility tunnels.

[0020] High reliability and controllability: Key process parameters and acceptance indicators such as grouting pressure, water-cement ratio, and solidification strength have been clearly defined, making construction quality controllable and results verifiable, forming a closed-loop synchronous information-based construction process (construction-monitoring-feedback). Attached Figure Description

[0021] Figure 1 This is an elevation view of the composite anchor pile of the present invention; Figure 2 This is a plan view of the composite anchor pile of the present invention; Figure 3 yes Figure 2 Enlarged view of box A in the middle; Figure 4 This is a schematic diagram of the cross-sectional structure of the reinforcing bar of the present invention; Figure 5 This is a schematic diagram of the longitudinal section structure of the reinforcing bar of the present invention.

[0022] Figure label: 1. Bridge; 2. Bridge pile cap; 3. Open-cut trench; 4. Composite anchor pile; 5. Grouting body; 6. Reinforcing bar; 6-1. Isolation ring; 6-2. Longitudinal reinforcement; 6-3. Positioning support reinforcement. Detailed Implementation

[0023] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0024] Example 1 like Figure 1-3 As shown, in the construction of an open-cut utility tunnel near an existing urban road bridge 1, the open-cut construction isolation and reinforcement method of this invention was applied to protect the bridge piles. The steps include: 1) Determine the location of the isolation zone: A 0.5-meter-wide isolation zone was determined at a distance of 0.1-0.6 meters from the edge of the bridge pile cap 2, parallel to the excavation line of the utility tunnel.

[0025] 2) Construction of composite anchor pile group: 4 composite anchor piles are constructed within the isolation zone. The diameter of the composite anchor piles is F=150mm ( Figure 4 The diameter of the dashed circle in the diagram), the center-to-center spacing E = 400mm, refers to the distance between the centers of two adjacent composite anchor piles. Due to the low clearance under the bridge, a small geological drilling rig was used for drilling. The reinforcing bar 6 was fabricated in sections and extended at the borehole opening using a flash butt welding machine. Care was taken throughout the process to avoid collisions with the bridge structure, allowing for flexible construction within the limited space.

[0026] 3) High-pressure grouting to form a continuous reinforced grout body: A cement grout with a water-cement ratio of 1:0.5 is used, and high-pressure grouting is performed in layers through pre-embedded sleeve valve pipes. The grouting pressure is dynamically controlled between 0.5 and 1.0 MPa to ensure that the grout diffusion radius R ≥ 250 mm (meeting the requirement of R ≥ 0.5E = 200 mm), allowing the grout bodies of adjacent piles to reliably overlap, forming a continuous vertical reinforced isolation wall. This vertical reinforced isolation wall is 10 meters long and 4 meters deep. During the actual construction process, isolation walls of other sizes can be set according to the specific terrain environment; they can be longer or shorter, or deeper or shallower, etc.

[0027] like Figure 4-5 As shown, the reinforcing bar 6 used in this embodiment includes an isolation ring 6-1, longitudinal reinforcing bars 6-2, and positioning support reinforcing bars 6-3. Isolation rings 6-1 are welded every 1 meter along the length of the longitudinal reinforcing bars 6-2. Several positioning support reinforcing bars 6-3 are evenly arranged on the isolation rings 6-1 perpendicular to the longitudinal reinforcing bars 6-2. In this embodiment, the isolation ring 6-1 is a ring-shaped component made of 12mm diameter threaded reinforcing bars, with an inner diameter of 30mm. The longitudinal reinforcing bars 6-2 are 20mm diameter threaded reinforcing bars, typically arranged in a triangular pattern of three bars. The isolation ring 6-1 is located inside this triangular arrangement of longitudinal reinforcing bars and is fixedly connected by welding. The positioning support reinforcing bars 6-3 are 12mm diameter threaded reinforcing bars, typically arranged in three evenly spaced bars on one isolation ring, and fixed to the isolation ring by welding. In this embodiment, there are 5 isolation rings, 3 longitudinal reinforcing bars, and 15 positioning support reinforcing bars.

[0028] 4) Repeat steps 1)-3) to construct multiple rows of vertically reinforced isolation walls. In this embodiment, a total of 4 rows are arranged.

[0029] 5) Effect Verification and Process Monitoring: Core sampling verified that the unconfined compressive strength of the vertically reinforced isolation wall reached 0.8 MPa, exceeding the design requirement of 0.5 MPa. During subsequent excavation of the utility tunnel, monitoring data showed that the horizontal displacement and settlement of the bridge pile foundations were far below the control values, effectively demonstrating the superior effect of this invention.

[0030] 6) After all the composite anchor piles have been constructed, proceed with the construction of open excavation sub-trenches 3.

[0031] All aspects not described in detail in this invention can be covered using conventional technical knowledge in the field.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for open-cut construction to isolate and reinforce adjacent existing structures, the method comprising the following steps: 1) Determine the location of the isolation zone: Between the planned open-cut area and the existing structures, determine a strip-shaped area parallel to the edge of the open-cut area as an isolation zone; 2) Construction of composite anchor pile group: In the isolation zone, multiple composite anchor piles are constructed along its direction at a center-to-center spacing E; the construction of the composite anchor piles includes drilling, placement of reinforcing bars and high-pressure grouting; 3) High-pressure grouting forms a continuous reinforced body: During high-pressure grouting, the grouting pressure is controlled so that the effective diffusion radius R of the grout in the soil satisfies: R ≥ 0.5 × E, thereby ensuring that the grouting bodies of adjacent composite anchor piles overlap each other to form a continuous vertical reinforced isolation wall. 4) Effect verification and process monitoring: Verify the unconfined compressive strength of the vertically reinforced isolation wall and conduct real-time monitoring of the existing structure during subsequent open-cut construction.

2. The open-cut construction isolation method according to claim 1, characterized in that, In step 2), the diameter F of the steel bars in the composite anchor pile is 150mm and the center-to-center spacing E is 400mm.

3. The open-cut construction isolation method according to claim 1, characterized in that, In step 3), the grout is a cement grout with a water-cement mass ratio of 1:0.5, and the grouting pressure is 0.5MPa to 1MPa.

4. The open-cut construction isolation method according to claim 1, characterized in that, In step 4), the unconfined compressive strength of the vertically reinforced isolation wall is not less than 0.5 MPa.

5. The open-cut construction isolation method according to claim 1, characterized in that, The steel bar includes isolation rings, longitudinal steel bars, and positioning support steel bars. Isolation rings are set at intervals along the length of the longitudinal steel bars, and several positioning support steel bars are evenly arranged on the isolation rings perpendicular to the longitudinal steel bars.

6. The open-cut construction isolation method according to claim 5, characterized in that, The isolation ring is a ring-shaped component formed by threaded steel bars; three longitudinal steel bars are arranged in a triangle, and the isolation ring is located inside the longitudinal steel bars arranged in the triangle; three positioning support steel bars are evenly arranged on an isolation ring, spaced apart from the longitudinal steel bars.

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