【作者】 雷晓雨；

【导师】 闫澍旺；

【作者基本信息】 天津大学 ， 岩土工程， 2012， 博士

【摘要】 CFG桩是水泥粉煤灰碎石桩Cement-flyash-gravel Pile的简称,是建设部“七·五”计划课题,于1988年立题进行试验研究,并从80年代末开始在工程中应用。通过二十余年的科研和工程实践,CFG桩复合地基技术不断完善,现已列入国家行业标准《建筑地基处理技术规范》(JGJ79-2002)。CFG桩复合地基常规等承载力设计方法将基础下的地基加固到相等的承载力,然后确定基础面积并确定桩数布桩,有时因要求的加固后复合地基承载力不尽合理,可能导致布桩困难或不经济;特别是遇有两相邻柱荷载水平相差较大时,控制柱间沉降差难度加大。CFG桩复合地基多用于足够刚度基础下的地基处理。足够刚度基础具有向桩上转移荷载的能力,在给定褥垫厚度条件下桩和桩间土承载力都能较充分发挥。用规范方法对足够刚度基础下的复合地基承载力和变形计算的结果与实测情况比较吻合。在公路、铁路路基和油罐基础下的地基处理工程中,由于上部基础刚度很小,基础向桩上转移荷载的能力很弱,这类柔性基础下CFG桩复合地基桩土应力特性值得进一步探讨。针对这两大问题及与之相关的其它问题,本文进行了以下几个方面的研究探索工作:1.针对等承载力设计方法的不足,论文提出非等承载力设计方法,以独立基础下CFG桩复合地基设计为例,从中心受压基础和偏心受压基础两个方面出发根据算例得出CFG桩复合地基非等承载力设计方法的重要计算公式和一般计算步骤。2.地下水问题也是CFG桩复合地基设计中常见的问题,论文通过理论分析,分别讨论地下水对基底压力、基底附加压力、基础反力以及对地基承载力进行深度修正的影响,得出地基中存在地下水时的设计方法。3.通过中石化大型油罐工程现场试验和实测资料,探究柔性基础下CFG桩复合地基桩土应力特性。4.尝试应用大型数值分析软件模拟工况,结合现场实测数据提出规范中采用刚性荷载板做柔性基础下CFG桩复合地基检测没有意义,静载试验只适用于足够刚度下CFG桩复合地基。更多还原

【Abstract】 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.更多还原