【作者】 赵秀绍；

【导师】 汤凤林；

【作者基本信息】 中国地质大学 ， 地质工程， 2006， 博士

【摘要】 CFG(Cement Fly-ash Gravel)桩是水泥粉煤灰碎石桩的简称，就本质而言，CFG桩复合地基是对碎石桩复合地基的继承与发展。CFG桩复合地基可以灵活地改变桩长、桩间距、褥垫层厚度和桩体配合比来满足承载力和沉降变形的要求，加上CFG桩可以充分利用桩间土的承载力、桩身材料可以消除大量工业废料——粉煤灰，可在降低工程成本的同时保护环境，经济和社会效益十分显著。 2002年初，新规划的郑东新区CBD(中央商务区Central Business District)方案出笼，引发郑州市东郊的建设热潮。建设郑东新区成为郑州大都市化的重要发展战略，这给高效低价的长螺旋CFG桩复合地基技术提供了广阔的应用空间。然而长螺旋CFG桩复合地基技术应用于郑东新区的饱和粉土层、粉质粘土层时，常出现窜孔、引起周围土体及周围建筑物开裂等问题。在郑东新区，许多施工单位进场施工数排桩后即面临该问题，被迫停工并撤走设备，造成巨大的资金损失及劳动力浪费。2003年7月，在郑州举行了郑东新区CBD中心岩土工程与地下空间资源利用高级论坛，与会专家讨论了在郑东新区的长螺旋CFG桩施工引起的工程环境问题，专家组针对CFG桩施工做出了比较模糊的结论：“有条件地采用CFG桩或其它复合地基”。 长螺旋CFG桩在郑东新区施工过程中，存在着以下问题：①桩间土孔隙水压力(简称孔压)变化规律不明；②施工影响范围不明；③孔隙水压力发展与窜孔、土体拉裂之间的关系不明。因此政府主管部门不得不出面干涉这项技术的推广应用。例如郑东新区管理委员会曾下文明确要求一般不提倡使用，特别是施工周围有建筑及重要管线的建筑场地，若采用CFG桩方案应经特殊审批。可见长螺旋CFG施工引起工程环境问题已经严重制约了长螺旋CFG桩在郑东新区的应用，研究长螺旋CFG桩施工引起工程环境问题的机理及应对措施迫在眉睫。 据此本文提出了长螺旋CFG桩施工引起工程环境问题的概念与研究目的。文中长螺旋CFG桩施工引起工程环境问题是指由于长螺旋CFG桩施工造成周围建筑物开裂及相邻桩窜孔的问题。其研究目的是得出长螺旋CFG桩施工引起工程环境问题的机理及影响因素，在此基础上提出应对措施。因而，本文以郑东新区为例进行长螺旋CFG桩施工引起工程环境问题的研究，为提高长螺旋CFG桩施工水平，促进该技术在郑东新区的应用具有重要的现实意义。 本文以河南省科技攻关项目“长螺旋管内泵压桩复合地基技术在饱和粉土中的适应性更多还原

【Abstract】 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更多还原