The Experimental Research & Finite Element Analysis Of Engineering Environmental Problems Caused By CFG Pile Construction

CFG pile is the abbreviation of Cement Fly-ash Gravel pile. In essence, CFG pile composite foundation is derived from gravel pile composite foundation. CFG pile composite foundation may enhance bearing capacity and reduce settlement by changing pile length, pile distance, cushion thickness and mixture ratio of pile. In addition, it can make the best use of bearing capacity of ground between piles, and eliminate lots of industrial waste fly-ash. Because the technology can protect environment while reduce project cost, its economical and social benefit are significant.At the beginning of 2002, the new planned project of the CBD in Zhengdong New District causes high-tide of construction in Zhengzhou eastern suburb. The construction in Zhengdong New District became an important strategy for urbanization in Zhengzhou, Which provides an extensive application field for long spiral CFG pile composite foundation for its high efficiency and low price. But when long spiral CFG pile composite foundation technology is applied in saturated silt and saturated silty clay in Zhengdong New District, it often causes problems such as flee-bore, ground dehiscence, building dehiscence etc. In Zhengdong New District, Building dehiscence problems appeared after several rows piles construction. The construction equipment is compelled to shutdown and withdraw, which causes the huge fund loss and labor force waste. A senior forum about the Zhengdong New District CBD center's geotechnical engineering and underground spatial utilization was held in Zhengzhou in July 2003. The experts discussed the problems caused by CFG construction in Zhengdong New District and drew an ambiguous conclusion in view of the CFG pile construction "CFG pile or other kinds of composite foundation can be conditionally adopted".In Zhengdong New District, there are several uncertainties in long spiral CFG pile construction process. Such as pore water pressure changing rule is unclear, the scope of construction influence is unclear, the relationship between pore water pressure and flee-bore & soil body dehiscence is unclear etc. So government has to intervene to promote the application of this technology. For example, the Zhengdong New District management committee once issued that the using of CFG pile can not be recommended, especially there are buildings and important underground pipe lines around construction area, if CFG pile is adopted special approval should be authorized. This has seriously hindered promotion and application of the CFG pile composite foundation technology in Zhengdong New District, so the mechanism study of engineering...