Foundation pit support is a measure to support, reinforce and protect the side wall and surrounding environment of foundation pit to ensure the safety of underground structure construction and surrounding environment of foundation pit.
Zhong Da Consulting Bianxiao Company combed the relevant contents, and the basic situation of foundation pit support is as follows:
Common types of foundation pit support:
1. Pile row support, pile support, pile anchor and pile row cantilever;
2. Diaphragm wall support, diaphragm wall+support;
3. Cement retaining wall;
4. Steel sheet piles: steel sheet piles are supported by transverse baffles and steel sheet piles;
5. Soil nailing wall (shotcrete and bolt support);
6. Inverted arch wall;
7. Place undisturbed soil on the slope;
8. Support in foundation pit;
9. Pile wall support system;
10. Simple horizontal support;
1 1. Reinforced concrete pile;
12. Reasonable combination of two or more of the above methods, etc.
Content of technical scheme for foundation pit support:
(a) the construction plan
1. Before foundation construction, geological exploration and understanding of underground pipelines must be carried out, and a special construction scheme should be worked out according to soil conditions and foundation depth. The construction scheme should conform to the actual situation of the construction site and can guide the actual construction. Its contents include: slope setting requirements or supporting structure design, mechanical selection, excavation sequence and excavation depth by layers, ramp position, foundation pit load, vehicle access to roads, dewatering and drainage measures and monitoring requirements. Corresponding measures should be taken for important underground pipelines.
2. Foundation construction should be supported. If the depth of the foundation pit exceeds 5M, the supporting structure of the foundation pit must be designed and calculated according to relevant standards, and there are design calculations and construction drawings.
3. The construction scheme must be approved by the technical director of the enterprise and signed and sealed before implementation.
(2) Border protection
1. Edge protection must be carried out in foundation pit construction. 1.2M high railings can be used to protect the limb with a depth of less than 2M, and closed protection must be used for foundation pit construction with a depth of more than 2m.
2. The distance between the limb protective railing and the edge of the foundation pit shall not be less than 50 cm.
(3) pit wall support
1. The slope set during foundation pit excavation meets the safety requirements. The practice of pit wall support and the reinforcement measures of important underground pipelines must meet the requirements of special construction scheme and design scheme of foundation pit supporting structure.
2. When the supporting facilities are partially deformed, the scheme shall be put forward in conjunction with the designers, and corresponding measures shall be taken in time to adjust and reinforce them.
(4) Drainage measures
1. Effective drainage and dewatering measures shall be set according to the construction scheme for foundation pit construction.
2. If dewatering outside the pit is used in deep foundation pit construction, measures must be taken to prevent the dangerous settlement of adjacent buildings.
(5) Pit load
1. The quantity of soil and materials piled and the distance from the foundation pit edge shall meet the requirements of relevant specifications and construction schemes.
2. When the distance between the mechanical equipment construction and the edge of the foundation pit (groove) does not meet the relevant requirements, effective measures should be taken for the wall support and ground of the foundation pit within the scope of mechanical construction according to the construction plan.
(6) uplink and downlink channels
1. There must be a special passage for workers to get up and down in foundation pit construction.
2. Set the channel, must be solid and reliable structure, quantity and location meet the construction requirements and comply with the relevant safety protection regulations.
(7) Earthwork excavation
1. Before the construction machinery enters the site, it shall be inspected and accepted by the safety management department of the enterprise, and the acceptance record shall be kept.
2. Construction machinery operators should be trained and assessed according to regulations, hold relevant certificates, and be familiar with the safety technical operation procedures of this type of work.
3. During construction, excavation shall be carried out according to the construction plan and regulations, and the basement soil structure shall not be overbreak or destroyed.
4. The mechanical operation position should be stable and safe, and personnel are strictly prohibited from entering the working radius of the excavator.
(8) Monitoring
Deformation monitoring of foundation pit supporting structure should be carried out according to the plan, and monitoring records should be kept. Settlement observation should be made for adjacent buildings, important pipelines and roads, and observation records should be made.
The monitoring of foundation pit supporting engineering includes: supporting structure detection and surrounding environment monitoring.
1. Monitoring of supporting structure includes:
(1) Monitoring of lateral pressure, bending stress and deformation of retaining wall
⑵ Monitor the axial force and bending stress of the supporting anchor.
(3) the waist beam (purlin) axial force and bending stress monitoring.
(4) Monitoring the settlement and the lifting of the column
2. Monitoring of the surrounding environment
(1) Monitor the settlement and inclination of adjacent buildings.
(2) Monitoring of settlement and displacement of underground pipelines, etc.
(3) Monitoring of topographic deformation outside the pit
(9) Working environment
1. The workers in the foundation pit should have a stable and safe foothold.
2. Safety isolation and protection measures should be set when vertical and cross operations are carried out.
3. There should be sufficient lighting for construction at night or in dim light, and local lighting should not be installed in the workplace.
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