With the rapid development of economy and technology, the proportion of high-rise buildings and super high-rise buildings in urban construction is increasing year by year. How to solve the safety problem in deep foundation pit construction becomes more and more eye-catching. triggerThe foundation pitThe main problems of safety accidents are as follows:

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

(2) The top of the excavation slope is overloaded or the cohesion of the soil is destroyed due to vibration, which causes the damage of the soil structure and causes the landslide;

(3) Due to incorrect construction methods: incorrect excavation procedures, excessive height excavation, improper placement or removal of supports, or inadequate drainage and collapse during thawing.

In view of the above problems, in order to ensure the safe construction of foundation pit engineering, the construction scheme should be formulated and the corresponding safety protection measures should be taken according to the relevant provisions of the design specification of foundation pit supporting.

1, construction plan

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

2, the border guard

The foundation pitConstruction 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 PROTECTIVE RAILINGS AROUND THE FOUNDATION PIT SHOULD CONFORM TO THE "TECHNICAL CODE FOR SAFETY OF CONSTRUCTION HEIGHT WORK" FROM THE SELECTION OF MATERIALS, the WAY OF INSTALLATION TO THE degree of FIRMNESS.

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

4, 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 uneven settlement of surrounding buildings. The control methods of groundwater generally include drainage and precipitation.

5, pit side load

Code for piling earthwork and MATERIALS at the pit side, including that conveyments and machinery shall not be moved too close to the edge of the groove, and that the piling of earthwork shall not be less than the upper edge of the groove1.2m, the height of the abandoned mound shall not exceed1.5m.

6, Up and down the channel

(1) Special access for operators must be provided. During foundation pit construction, operators are not allowed to climb the board and scaffolding, and must pass through the special channel 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 built according to the conditions, and shall meet the requirements of climbing operations in the specification for high work.

7, earthwork excavation

(1) All construction machinery shall enter the site in accordance with regulations, pass the acceptance inspection organized by relevant departments, confirm the qualification, and have records.

(2) When mechanical excavation and manual excavation are coordinated, the operators shall not enter the radius of the excavator; After the excavator stops operation, the operator can clean the bottom of the pit and find the slope.

(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

The foundation pitIn the process of excavation, it is necessary to carry out information monitoring of the foundation pit, 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

In the construction of foundation pit, the underground operation condition should not be ignored, and the operation in the pit should not be reduced.

(1Personnel operations must have a safe foothold, scaffolding erection must meet the specifications, border protection must meet the requirements.

(2(In cross operation and multi-layer operation, isolation layer should be set up above and below; In vertical transport operations, the equipment must be checked in accordance with the corresponding specifications.

(3) deepThe foundation pitThe construction, setting of electrical boxes, surrounding environment and erection and use of various electrical equipment should comply with electrical specifications.

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