水泥土软化特性及复合地基沉降计算研究

【作者】 欧明喜；

【导师】 曾芳金；

【作者基本信息】 江西理工大学 ， 岩土工程， 2009， 硕士

【摘要】 复合地基是在天然地基土体中设置加固体的一种人工地基。水泥土桩复合地基是复合地基的一种,在土木工程中有着广泛的应用。虽然大家公认水泥土跟超固结土一样具有应变软化特性,但是,对水泥土软化特性及对能反应软化特性的应力应变关系的研究却少之又少。目前,复合地基沉降计算水平远低于复合地基承载力计算水平,也远远落后工程实践的需要。这极大地制约了复合地基的推广和进一步发展。针对这些问题,本课题对水泥土的软化特性和应力应变关系进行了试验研究。在此基础上总结了水泥土的软化特性并证明了文中所述表达式能够很好地拟合水泥土具有软化特性的应力应变关系。然后对现有计算复合地基加固区沉降量使用的桩体压缩模量取值进行了分析和改进,最后对现有的软弱下卧层沉降计算的分层总和法进行改进,提出了改进的分层总和法。本文首先总结了当前水泥土及复合地基的研究现状和本文研究的理论基础。根据室内试验的结果分析,总结了水泥土的相关软化特性。通过试验结果分析发现,峰值强度随围压的增大而增大,随水泥掺量的增大而增大,临界应变(峰值应力时的应变)随围压增大而增大,随水泥掺量增大而减小,残余强度随围压的增大而增大,随水泥掺量的增大而增大。通过室内试验结果曲线与拟合曲线进行了对比发现文中所述的应力应变关系能够很好的拟合水泥土具有软化特性的应力应变关系曲线。本文对现有的规范法计算复合地基加固区沉降时桩体压缩模量取值进行了分析,根据水泥土的应力应变关系对其提出了改进意见,并通过实例对其应用于计算复合地基加固区沉降过程进行了阐述。最后利用复合地基加固区沉降计算规范法的基本思想,对现在计算软弱下卧层沉降量的分层总和法进行改进,提出了改进的分层总和法。通过对工程实例的计算分析可知改进的分层总和法比现有的分层总和法及规范法计算更加简单且结果更为准确。这些方法对水泥土搅拌桩复合地基的设计与施工有一定参考价值。更多还原

【Abstract】 Composite foundation is a kind of artificial foundation setting up reinforcement body in natural soil. Cement-soil pile is one type of composite foundation and it has been widely adopted in civil engineering projects in China. Although the cement-soil is recognized by all with the same strain softening properties as super-consolidation soil, but the study on softening characteristics of the cement-soil and the relationship between stress and strain are few. At present, the level of settlement calculation of composite foundation is far lower than to determine the bearing capacity of composite foundation, far from the needs of engineering practice. which greatly restricted the application of composite foundation and the promotion of further development. To solve these problems, the softening characteristics of the cement-soil and the relationship between stress and strain are studied by testing on this basis, summed up the softening characteristics of cement-soil and proved the expression which be able to reflect the relations between stress and strain. Then the existing calculation of composite foundation reinforcement settlement areas used by the pile-compression modulus values were discussed and improved.At last,the improved method called sum of the hierarchical layers method and which made for the calculation of weak underlying layers is gave out.First of all, this article summarizes the current research about soil-cement and composite Foundation based on laboratory test results. Through analysis of test results found that the peak intensity increases with the increases of pressure and cement content, the critical strain increases(strain when the stress is the max) with the pressure increases, and decreased with the Cement volume increased,the strength of the residual increases with pressure increases and cement volume. The article introduced the relationship between stress and strain can be a good-fitting cement-soil stress-strain curves by comparing the curve of laboratory test results and the fitting curve.In this paper, the present method of calculation of composite foundation reinforced area when the pile settlement body compression modulus values were analyzed. Improvements are proposed according to the soil cement the relationship between stress and strain on their. An examples used in the calculation of its composite foundation reinforcement of settlement areas described the process.The method of calculating the composite foundation reinforcement is thought, the improved method is gave out.Through the project examples we can see that the improved method is easier to carry out and the results are more accurate. These methods can be used for designing and construction of mixing cement pile.更多还原