With the enlargement of underground spaces, underground transformer substations and underground supermarkets become more and more. The scale of construction becomes bigger and the deep foundation pit projects increase. While the traditional approach for deep foundation pit project can’t meet the demand of current underground constructions.
Nowadays, the common forms of deep foundation pit support are row pile support, diaphragm wall support, cement retaining wall support, armor plate pile support and rock bolt support, etc. While as for deep foundation pit support, there are several aspects need to be noticed:
1. Manipulation of underground water.
During the period of digging deep foundation, manipulation of underground water is also a part of support. It involves water collection, drainage system, water interception and water recharge system, etc.
2. Preparation for construction supporting.
Geological condition and underground pipelines should be explored before construction. After that can go on with the design of supporting structure, choosing machine, and the proper design of digging depth, slope location and load capacity.
3. Protection of the border.
Deep foundation pit support should protect the border. 1.2 m high-rail is adopted for pits that was less than 2m in depth, closely-knitted safety net is necessary for pits over 2m. The distance between protection rail and pit entrance should be over 50cm.
4. The support of pit wall.
The excavation of pit wall should be carried out according to the requests. If deformation occurred, relevant measures should be adapted timely.
5. The carrying capacity.
The location of mound and materials should have certain distance to the entrance of pit. Machines and equipment should work in specific areas, avoiding collapse.
6. The construction of passageways.
Specialized passageways should be constructed for workers. It must be solid and reliable enough to guarantee workers’ safety.
7. Foundation pit excavation.
Before working, safety management department should check working places and machines. Workers should accept trains and operation specifications and excavate soil according to the schedule strictly.
8. Monitoring and recording.
Deep foundation pit should be monitored for avoiding deformation. Surrounding buildings, pipelines and roads should be observed and recorded regularly, once ground subsidence appears, effective measures should be taken.