【作者】 贺为民；

【导师】 李智毅；

【作者基本信息】 中国地质大学（北京） ， 地质工程， 2008， 博士

【摘要】 深层搅拌法是一种常用的地基处理方法,目前在复合地基和止水帷幕中被广泛应用。论文在前人研究的基础上,结合实际工程需要,通过现场试验和理论分析,取得了以下研究结果。(1)利用前人研究成果,分析了影响水泥土强度和深层搅拌桩桩身强度的主要因素,提出了提高深层搅拌桩桩身强度的措施。(2)现场粉喷桩单桩、多桩复合地基载荷试验实测数据对比分析表明,粉喷桩复合地基承载力基本值随着复合地基载荷试验中桩数的增加而降低;复合地基变形模量随着载荷试验中桩数增加而减小;在同级荷载下,沉降量随着复合地基载荷试验中桩数增加而明显增大。根据复合地基载荷试验结果,初步提出了深层搅拌桩复合地基压缩模量群桩效应系数。(3)采用有限差分方法,建立了深层搅拌单桩、多桩复合地基数值分析模型,采用FLAC3D程序,获得了深层搅拌桩复合地基应力和位移分布规律。(4)研究了深层搅拌桩复合地基沉降量的计算方法,探讨了影响复合地基工程造价的主要因素,提出了通过求取复合地基中总桩长(单桩长度总和)最小值来实现复合地基优化设计的思路。建立了矩形基础下(轴心荷载作用时)深层搅拌桩复合地基优化设计的数学模型,以单桩长度和桩间距为优化设计变量,推导了深层搅拌桩复合地基优化设计的计算公式,编制了相应的计算程序。分析了影响总桩长最小值的主要因素,提出了一些优化设计的建议。(5)在深层搅拌桩止水帷幕设计中,指出了采用传统深层搅拌桩水泥掺入比公式计算水泥掺入量存在的浪费,推导出了深层搅拌桩止水帷幕水泥掺入比计算公式和厚度计算公式,经实际工程使用效果较好,并具有一定的经济效益。(6)从实际工程需要出发,在深层搅拌桩止水帷幕中提出了视搭接宽度的概念和大搭接宽度设计施工方法,较好地解决了止水帷幕中桩间开叉漏水的问题;大搭接宽度施工方法与传统搭接宽度施工方法相比,还具有较好的经济效益。(7)在地下可用空间狭小的场地,提出了在单排深层搅拌桩止水帷幕中套打钻孔灌注桩基坑支护截水技术设计方法和施工工艺,成功地解决了施工场地狭小的困难。更多还原

【Abstract】 Deep-mixing technique is one of common ground improve methods and widely used in composite foundation and curtain for cutting off water. On the basis of former research achievements of other scholars and also combined with practical engineering requirements, the following results with in-situ tests and theory analysis were obtained.(1) The measure of improving strength of deep-mixing pile was proposed after main influence factors on strength of cement-soil and deep-mixing pile were analyzed using research results of other scholars.(2) Comparison and analysis on load tests in composite ground of single and multi-piles of spout powdered piles show that basic value of bearing capacity and deformation modulus of composite ground decrease with increase of the number of piles in load test and that settlement increases obviously with increase of the number of piles in load test under same-class load. Based on the results of composite ground load tests, the pile group effect coefficient of compressive modulus of deep-mixing pile composite ground was given.(3) Numerical model of composite ground of single and multi-piles of deep-mixing piles was built using finite-difference method. Using program FLAC3D, the distribution of stress and displacement of deep-mixing pile composite ground was obtained.(4) The settlement calculation method of deep-mixing pile composite ground was studied. The ideas to realize optimization design of composite ground through computing minimum value of total pile length in composite ground was proposed after main influence factors on engineering price of composite ground were discussed. Mathmatic model of optimization design of deep-mixing pile composite ground with rectangle foundation under axial load was built. Using length of single pile and pile distance as variable, the calculation formulas of optimization design of deep-mixing pile composite ground were deduced, and the calculation program was coded The main factors which affect the total pile length were analyized and some suggestions of optimization design were proposed.(5) In the design of curtain for cutting off water in deep-mixing piles, it is proposed that there is waste of cement content calculated by traditional formula of cement-mixed proportion. Calculation formulas of cement-mixed proportion and thickness of curtain for cutting off water in deep-mixing piles were deduced. The good effectiveness and economical benefit are achieved after practical engineering application.(6) The problem of water leakage from curtain for cutting off water is reasonably solved after the conception of apparent connection width and construction method of big connection width in curtain for cutting off water in deep-mixing piles are proposed from practical engineering need. The economical benefit of the construction method of big connection width is better than that of construction method of traditional connection width.(7) The difficult of narrow construction site is successfully solved after the design method and construction technology of support and water cut-off technique for the foundation pit with bored piles drilled in single-row deep-mixing piles of curtain for cutting off water are proposed in the narrow available site of the underground.更多还原