Lead toThe foundation pit The main causes of safety accidents are as follows:

(1) The excavation slope of the foundation pit is not enough, and the slope is not released according to the category of soil, the allowable slope value and the specified aspect ratio, resulting in the collapse of the foundation pit.

(2The top of the foundation pit slope is overloaded, or the cohesion of the soil is destroyed by the vibration, which causes the damage of the soil structure and causes the landslide.

(3) Collapse due to incorrect construction methods, incorrect excavation procedures, excessive excavation, incorrect placement or removal of supports, inadequate drainage and thawing.

In view of the above problems, to ensure thatFoundation pit engineeringThe construction plan should be formulated according to the relevant provisions of the design specification of foundation pit support, and corresponding safety protection measures should be taken.

1, construction plan

Before foundation pit excavation, the supporting scheme should be determined according to the soil quality, depth of foundation pit and surrounding environment, which should include: slope discharge requirements, support structure design, mechanical selection, excavation sequence, layered excavation depth, ramp location, vehicle access road, dewatering measures and monitoring requirements.

2, the border guard

When the foundation pit construction depth reaches2mIf the operation on the edge of the pit has become dangerous, in accordance with the provisions of the operation on the height and the operation near the edge, the border protection facilities should be set up. The MATERIAL SELECTION, WAY AND FIRMNESS OF THE PROTECTIVE RAILINGS AROUND THE FOUNDATION PIT SHOULD COMPLY WITH THE PROVISIONS OF "TECHNICAL CODE FOR SAFETY OF CONSTRUCTION WORK IN HIGH PLACES".

3, pit wall support

Different depth of foundation pit and operating conditions, the adopted support methods are also different.

(1) undisturbed soil is sloped

Generally, the foundation pit depth is less than3mCan be used one-time slope. When the foundation pit depth reaches4~5mCan also be used for grading slope. The stability of the slope must be ensured by open excavation and caving. If necessary, the method of pile driving, soil nailing wall or diaphragm wall should be adopted to ensure the stability of the slope.

(2) pit support

The supports in the pit can be single-layer or multi-layer supports. The supporting materials are usually shaped steel or reinforced concrete. When erecting the supports, attention must be paid to the installation and removal sequence of the supports. Especially for multi-layer support to strengthen the management, concrete support must be in the upper support strength80%When can dig the lower layer; The section steel support is strictly prohibited to be welded under load.

Drainage measures

Underground water is often encountered in foundation pit construction. Poor treatment of deep foundation pit construction will not only affect foundation pit construction, but also cause the risk of uneven settlement to surrounding buildings. The control methods of groundwater generally include drainage and precipitation.

The pit load,

The piling of earthworks and materials at the pit side, including the movement of conveyments and machinery along the edge of the excavated earthworks, shall not be too close to the edge of the groove, and the piling of earthworks shall not be less than the upper edge of the groove1.2m, the height of the abandoned mound shall not exceed1.5m.

6, upper and lower channels

(1Dedicated passageways must be set up for foundation pit construction personnel, and no climbing board or scaffolding is allowed to ensure safety.

(2The special passageway for personnel shall be determined in the construction organization design, and the climbing facilities shall be constructed by ladders or specially constructed according to the conditions, which shall meet the requirements of climbing operations in the specification for high work.

7, earthwork excavation

(1All construction machinery shall enter the site according to the regulations, and be accepted and confirmed by relevant departments, and records shall be kept.

(2Personnel shall not enter the radius of excavator when mechanical excavation and manual excavation are carried out in coordination. When it is necessary to enter, personnel can clean the bottom of the pit and find the slope until the excavator stops working.

(3The excavator can not exceed the height of the soil, so as not to cause damage to the soil structure. The last part of earthwork left at the bottom of the pit should be done manually, and the manual earthwork should be done before the bedding to reduce the time of brightening the groove.

8, foundation pit retaining deformation monitoring

In the process of foundation pit excavation, the foundation pit information monitoring should be carried out, mainly aiming at the deformation of the supporting system, the ground settlement or uplift deformation outside the foundation pit and the dynamics of adjacent buildings. In case of over-limit deformation, measures should be taken immediately to ensure construction safety.

9, operating environment

The foundation pitDuring construction, underground working conditions should not be ignored, nor should requirements be reduced for working in pits.

(1) Personnel must have a safe foothold when working, scaffolding must meet the specifications, and border guards must meet the requirements.

(2) Cross operation, multi-layer operation, set up and down the isolation layer. Vertical transport equipment must also be inspected in accordance with the corresponding specifications.

(3The construction of deep foundation pit, the setting of electric box, the surrounding environment and the erection and use of various electrical equipment should comply with the electrical code.

Shanghai Qiangqiang Foundation Engineering Co., LTD. 's business covers foundation pit engineering, pile foundation engineering, land and waterFoundation treatment, slope treatment and other engineering fields. Around" Excellent technology, reliable process", construction fast "technical requirements,Is to provide customers with land, water foundation engineering technical consultation, construction services and other comprehensive solutions of the entity enterprise.Contact Number: 400-100-2850