【作者】 刘志明；

【导师】 李建中； 张可能；

【作者基本信息】 中南大学 ， 地质工程， 2007， 硕士

【摘要】 南沙开发区位于珠江三角洲的最南端，该地区广泛分布的深厚软土层是大规模基础工程建设中面临的最大的工程地质问题之一。搅拌桩复合地基在南沙处理软土已经得到了大规模的应用，但在工程设计中仍然存在着一些问题。随着复合地基理论的不断发展和完善，基于对各种不同桩体的荷载传递机理和变形控制等方面的深入认识，长短搅拌桩复合地基倍受关注。作为一种较新且有良好应用前景的技术方法，许多学者对其进行了研究并取得了一定的成果。但是，人们对此新型复合地基的研究还不够深入，对其工作性状、承载力和沉降量计算方法等方面的研究很少，并未形成完善和公认的设计理论和设计方法，许多问题还有待进一步的研究和工程实践的证实。本文主要研究内容和成果如下：(1)调查研究了南沙地区软土的特性。南沙地区软土为近代沉积的滨海相软弱粘性土，具有天然含水量高、天然孔隙比大、压缩性高、固结系数小、粘聚力小、承载力低、触变性较强等特点。(2)在南沙地区选择试验场地，设计了长短搅拌桩复合地基的现场载荷试验，并通过各种测量仪器测试和分析了复合地基的应力、沉降、孔隙水压力、桩土应力比等。(3)通过室内水泥土试验和室外检测数据的分析对比，研究了南沙地区水泥土的基本物理力学性质，并且认为：处理南沙软土中的腐殖质，加入2％的生石灰是经济可行的。(4)通过载荷试验数据，建立了南沙地区单桩复合地基载荷试验承载力与四桩复合地基载荷试验承载力的关系，为南沙地区以后的工程检测提供了依据；提出了南沙地区长短搅拌桩复合地基长、短搅拌桩各自的应力修正系数。(5)应用ADINA8．1有限元程序模拟分析了等长搅拌桩复合地基及长短搅拌桩复合地基，讨论了其位移场、应力场和应变场的分布规律，并将两者进行了对比，认为长短桩复合地基在处理深厚软土时有较好的经济性。更多还原

【Abstract】 The Nansha Development Area lies in the south of the Zhujiang Delta. The supreme geological problem is the thick soft-clay in the cosmical basic construction.The cement mixed piles composite foundation was applied extensively in the Nansha Development Area, but there were some questions in the project design. Along with the development of the composite foundation theory, the transfer law of loading and settlement control were known. The long-short cement mixed piles composite foundation are more and more widely applied. Being a new and well technology, many scholars researched it and got much harvest. At the same time, the mechanism of working character, bearing capacity and settlement were not enough. The current design theory and design method are not perfect and recognized. There are many problems still need to be investigated and validated by engineering practice. The mostly content and conclusions are as follow:(1) The soil of Nansha was soft-clay of shore-sea facies. There are some characteristics of high natural water content, high natural coid ratio, high compressibility, small cohesion, low bearing capacity, strong thixotropy.(2) Design long-short cement mixed piles composite foundation loading test in Nansha. And measure and analyzed the stress, settlement, pore water pressure and the stress ratio of pile and soil.(3) Based on contrast the lab test and site test of cement-soil, the paper researched the basic physical and mechanical character, and thought that it was feasibility that joined 2% calces to dispose the humus in the soft-clay.(4) Found the bearing capacity expressions of the single pile composite foundation and four piles composite foundation in Nansha. And it offered a gist to project monitoring for later engineering. The stress correction factor of long-short cement mixed piles of composite foundation was suggested.(5) Apply finite element program(ADINA8.1)to simulate and analyze the same length and long-short cement mixed piles of composite foundation about their displacement field, stress field and strain field. Simulation results show that used the long-short piles composite foundation was more economical when it disposed the thick soft-clay.更多还原