What are the main risk sources during the construction of precipitation excavation of foundation pit

Main sources of risk:

1.The failure of the support caused by the failure of the steel support and coffering, resulting in the collapse of the underground wall enclosure structure;

2.ground subsidence, landslides, quicksand;

3.The foundation pit is close to the lake surface, and the collapse of the water surface protection will cause water in the pit and affect the safety of surrounding houses (such as the M4 line);

4.The earthwork is over-excavated, resulting in large deformation of the enclosure structure, and causing ground subsidence and cracking of the house;

5.Improper treatment of various pipelines on the outside of the foundation pit, if the fire or urban water supply pipes are cut, resulting in surface settlement, cracking and collapse of houses;

6.Improper precipitation of foundation pit causes the ground to tilt to the house. Therefore, only by improving the quality and prevention and control capabilities of engineering risks can major accidents be avoided.

Collapses, falls from heights, mechanical injuries, lifting injuries, electric shocks, etc.

1. Supporting structure.

1) Forming quality of supporting structure;

2) Whether there are cracks in the crown beam, support and purlin;

3) Whether there is a large deformation of the support and column;

4) Whether there is cracking or leakage of the waterproof curtain;

5) Whether there is subsidence, cracks and slippage of the soil behind the wall;

6) Whether there is soil gushing, quicksand, and pipe gushing in the foundation pit.

2. Construction conditions.

1) Whether there is any difference between the exposed soil condition after excavation and the geotechnical investigation report;

2) Whether the length of the excavation section and the thickness of the layer are consistent with the design requirements, and whether there is ultra-long and ultra-deep excavation;

3) Whether the surface water and groundwater discharge of the site are normal, and whether the foundation pit dewatering and recharge facilities are operating normally;

4) The ground load around the foundation pit, whether there is an overload of the pile.

3. The surrounding environment of the foundation pit.

1) Whether the underground pipeline is damaged or leaked;

2) Whether there are cracks in the surrounding buildings (structures);

3) Whether there are cracks and subsidence in the surrounding roads (ground);

4) The construction of adjacent foundation pits and buildings (structures).

4. Facilities. 1) The datum point and measuring point are in good condition;

2) whether there are any obstacles that affect the observation work;

3) Monitor the integrity and protection of components.

Those that meet one of the following five characteristics must be listed as a major hazard source:

1. The excavation construction will inevitably cause safety impact on adjacent buildings (structures) and facilities or have special protection requirements;

2. It is intended to continue to be used after reaching the design service life;

3. Change the current design scheme, deepen, expand and change the use conditions;

4. Adjacent engineering construction, including piling, foundation pit excavation, and dewatering construction, affects the safety of foundation pit support;

5. Foundation pit adjacent to water.

The following 12 situations should be classified as general hazards:

1. There are inferior materials, quality defects, component damage or other unfavorable conditions that affect the safety and applicability of foundation pit engineering;

2. The vibration and shear generated by the construction of supporting structures and engineering piles may cause flow soil, soil liquefaction, and seepage damage;

3. Serious leakage may occur in the water interception curtain;

4. The main traffic road is located within the influence range of foundation pit excavation, or the building pipelines and municipal pipelines around the foundation pit may produce leakage, pipe ditch water storage, or there are drainage pipes with strong sensitivity to leakage and deformation.

5. In the rainy season, the prestressed anchor rod set up by the soil nailing wall and shallow layer may fail or the bearing capacity may be seriously reduced;

6. The side wall is miscellaneous fill soil or special rock and soil;

7. Foundation pit excavation may produce excessive uplift;

8. There is a vibration load on the side wall of the foundation pit;

9. The internal support fails or is continuously damaged due to various reasons;

10. Transverse impact load may be generated on the supporting structure;

11. Typhoon, heavy rain or heavy rainfall precipitation construction power interruption, foundation pit drainage system failure;

12. The creep of soil nails and anchors produces excessive deformation and ground cracks.

The scope of the sub-project with greater risk: the excavation depth of more than 3m (including 3m) of the foundation pit earthwork excavation project.

The scope of the sub-project with greater risk than a certain scale: the earthwork excavation project of the foundation pit with an excavation depth of more than 5m (including 5m).

3. All 1, foundation pit support and precipitation engineering.

Foundation pit support engineering refers to the excavation depth of more than 3m (including 3m) of the foundation pit (groove) and the use of supporting structure construction; or although the foundation pit does not exceed 5m, the geological conditions and surrounding environment are complex, and the groundwater level is above the bottom of the pit.

2. Earthwork excavation engineering.

Earthwork excavation engineering refers to the earthwork excavation of foundation pits and grooves with an excavation depth of more than 3m (including 3m).

3. Formwork engineering.

All kinds of tool-type formwork projects, including sliding formwork, large formwork and special structure formwork engineering, etc.

4. Lifting and hoisting engineering.

5. Scaffolding engineering.

floor-mounted steel pipe scaffolding with a height of more than 24m-50 m; cantilevered scaffolding; hanging basket scaffolding; Discharge platform, etc.

6. Demolition and blasting works.

Works that are demolished by hand, mechanically or by blasting.

7. Temporary power projects.

8. Other dangerous projects.

installation and construction of building curtain wall; tensile construction of prestressed structure; construction of special equipment; construction of grid and cable membrane structure; Slope construction above 6m; 30m and above high-altitude work; The use of new technologies, new processes, and new materials may affect the quality and safety of construction projects, and has been administratively licensed, and there is no technical standard for construction.

Sub-projects that may have an impact on the facilities around the site and the safety of residents; Other construction sites and operations that are prone to major accidents, such as strong professionalism, complex technology, high risk, and crossing.

Under normal circumstances, the major hazards of construction mainly include: the construction of deep foundation pits, shafts and large pipe trenches in foundation engineering, the installation, dismantling and use of large machinery and equipment (tower cranes, freight elevators, etc.) and the violation of operating procedures in various lifting and hoisting projects, resulting in accidents such as overturning of machinery and equipment, structural collapse, and death; Scaffolding and formwork support in the erection and dismantling process is not standardized, and the operation is commanded in violation of regulations; Non-standard operations at height, illegal command and operation; The construction electricity consumption is not standardized; House demolition, blasting works in violation of regulations, etc.

1. Deep foundation pit engineering, (the main hidden danger is earthwork collapse).

2. Formwork engineering and support system. (The main hidden danger is the collapse of the formwork).

3. Lifting, hoisting, installation and dismantling engineering. (The main hazards are falls from heights and mechanical injuries).

4. Scaffolding engineering. (The main hidden danger is falling from a height).

5. Demolition and blasting works. (The main hidden danger is **).

6. Circuit system engineering. (The main hidden danger is electric shock, or even fire).

7. Miscellaneous. Additional Information:

1. Construction safety requirements.

1. Gantry cranes, tower cranes, etc. do a good job of foundation pad treatment. The lifting equipment must be inspected before it is allowed to be used.

2. The steel pipe scaffold must be erected in a standardized manner, and the technical plan for safe construction must be prepared.

3. It is strictly forbidden to use backward and eliminated construction equipment, equipment and processes, otherwise, all violations of safety production laws and regulations will be punished according to the requirements.

4. Safety protection facilities must be done in accordance with technical standards.

6. Establish and improve the responsibility system for safe production.

7. Do a good job in safety management, internal data management, and do a good job in safety evaluation.

8. Strictly implement national mandatory standards.

9. Safety management personnel should regularly go deep into the site to conduct safety inspections, find hidden dangers and rectify them in time, and eliminate hidden dangers in the bud. To achieve the "three irons", iron discipline, iron wrist, iron heart.

The focus of safety work is to grasp typical examples, accident prevention, basic work, and hidden danger investigation and rectification.

10. It is strictly forbidden to leave construction holes indiscriminately, and some retention is very dangerous, which may lead to the collapse of the house.

2. Safety inspection requirements.

1. Before each safety inspection, there should be a clear inspection item and inspection purpose, content, inspection standards, key points and key parts.

2. Find and solve problems in a timely manner, and deal with the potential safety hazards in a timely manner.

3. The potential safety hazards found in the process of safety inspection must be registered as the basis for rectification, provide safety dynamic analysis, and guide the decision-making of safety management according to the hidden danger records and safety dynamic analysis.

4. It is necessary to seriously and comprehensively carry out systematic, qualitative and quantitative analysis, and conduct detailed safety evaluation.

5. For large-scale and comprehensive safety inspections, the inspection content, inspection standards and inspection requirements should be clarified. According to the requirements of the inspection, the person in charge of the inspection should be clarified, and professionals should be assigned to participate in the inspection, and a clear division of labor should be carried out.

6. After the rectification of the rectification part is completed, the relevant departments should be notified in a timely manner, and personnel should be sent to conduct a review.

7. Fill in the inspection records carefully and in detail, especially the location and degree of potential safety hazards.

Hello, the main sources of danger in construction projects are:

1. Deep foundation pit engineering, (the main hidden danger is earthwork collapse).

2. Formwork engineering and support system. (The main hidden danger is the collapse of the formwork) 3. Lifting, hoisting, installation and disassembly engineering. (The main hidden dangers are falls from heights and mechanical injuries) 4. Scaffolding engineering. (The main hidden danger is falling from a height).

5. Demolition and blasting works. (The main hidden danger is **).

6. Circuit system engineering. (The main hidden danger is electric shock, and even leads to fire) 7. Others.

Earthwork collapse, formwork, scaffolding, tower crane collapse, object strike, mechanical injury, fall from height, electric shock, fire.

Special equipment accidents, etc.

There are several main categories:

1) Deep foundation pit: the excavation depth of the construction site is more than 5m (including 5m), or the depth is less than 5m, but the geological conditions and surrounding environment are extremely complex, and the groundwater level is above the bottom of the pit, trench (groove) engineering;

2) Underground excavation works;

3) High formwork: the height of the formwork support system of horizontal concrete components exceeds the containment, or the span exceeds 18m (including 18m), or the total construction load is greater than 10kN, or the concentrated line load is greater than 15kN The formwork support system;

4) Manual digging pile engineering;

5) 30m and above high-altitude work;

6) Demolition blasting or earthwork blasting with a blasting charge of more than 200kg;

7) The height is greater than 6m (including 6m), or the height is less than 6m, but the geological conditions are complex tall slopes;

8) installation and dismantling of construction lifts and tower cranes;

9) Attached lifting scaffolding, hanging basket scaffolding engineering;

10) large-scale lifting and hoisting projects;

11) Other construction sites and operations that are prone to major accidents, such as strong professionalism, complex technology, high risk, and cross operation.