Unequal Bearing Capacity Design Method Of CFG Pile Composite Foundation

Cement-flyash-gravel Pile(CFG pile) is one of'the seventh five'planned problem proposed by Ministry of Construction of China, which was established and tested in 1988, and employed in engineering from the end of age eighty. Through more than twenty years'scientific research and engineering experiment, the technology of CFG pile composite foundation is developed to perfect which is included in national trade standard"Technical Regulation of Architectural Ground Treatment"(JGJ79-2002).The designs of equal bearing capacity about CFG pile composite foundation compacts equal loads to ground base, confirms the area of foundation, and then ensure the numbers of disposal pile. Because of the required compacted composite foundation capacity is not so reasonable, which would lead to the difficulty and diseconomy of disposal pile; especially when the loads in adjacent piles unequal widely, it's difficult to control the differential settlement in piles. CFG piles composite ground are mostly used in ground treatment with enough rigidity foundation. Enough rigidity foundation could shift loads to piles, which makes the best of both capacity under the set mattress thickness. The result of capacity and deformation of composite ground in enough rigidity foundation with specificities method corresponded well with tested results. In the engineering of ground treatment like oil tank foundation, highway and railway subgrade, because of the little rigidity of upper foundation the weakness of capability to shift loads to piles, the analysis of stress behavior about CFG piles composite ground under such flexible foundation worth while to research. The main research work consists of the following parts.1. Proposed unequal bearing capacity design method countering the weakness of the equal one. With the example of CFG piles composite ground under independent foundation, derivated important formula and normal design method of CFG pile composite foundation bearing capacity from the aspects of centric and eccentric compression foundation.2. The exist of groundwater is another problem in design of CFG piles composite foundation. Through thesis analysis, discussed the impact of groundwater in the calculation of base pressure, foundation reaction force, base supplementary pressure and depth correction of bearing capacity, educed the calculation method when groundwater exist in foundation. 3. From the tested and measurement information of large scale oil storage tank experiment of Sinopec Group, explored the piles and soil stress behavior about CFG piles composite ground under flexible foundation4. Large numerical analysis software is attempted to simulate operating condition. Pointed that using rigidity load board to detect CFG pile composite ground under flexible foundation makes no sense. Steady load test is only adaptable to CFG pile composite ground with enough rigidity foundation.