【作者】 赵健；

【导师】 冷伍明； 曾胜；

【作者基本信息】 中南大学 ， 岩土工程， 2010， 博士

【摘要】 稳定和变形问题是在软土地基上建造建筑物遇到的两大主要问题,而软土的强度是软土地基稳定的决定性因素。软土随着排水固结强度不断增长是软土的重要工程特性之一,这种强度的增长对于低承载力的软土地基而言十分重要。掌握软土地基的强度增长规律是合理控制软土地基上路堤填筑速率、缩短工期、获得更科学、更经济的路堤填筑方法的基础。本文结合湖南省交通科技攻关项目,依托湖南省高速公路软土地基原位测试、软土强度参数室内外试验、理论推导和分析等方法对山间洼地软土地基强度特性、强度增长计算方法和工程应用进行了些探索,主要研究工作和成果如下：(1)比较系统地对山间洼地软土地基进行了三种原位测试强度对比试验,建立了十字板抗剪强度Cu与轻便动力触N10的回归公式,为试验地区的山间洼地软土原位测试强度分析奠定了基础。(2)对山间洼地软土进行了大量系统的物理力学指标试验,用统计回归的方法建立了山间洼地软土物理力学指标、室内试验强度指标与原位试验强度指标之间的回归方程。在试验数据的基础上,进行了软土强度指标的灰色关联度计算,分析了各物理力学指标对软土强度影响的敏感性。试验成果为掌握山间洼地软土的工程特性提供参考。(3)进行了软土的固结和直剪试验,研究了不同固结压力作用下,抗剪强度指标c、φ随固结度(时间因素)的变化规律,以及一次性加载与逐级稳定加载对抗剪强度增长规律的影响,并建立了软土抗剪强度室内试验参数c、φ与固结度的拟合方程,其对软土路基的安全填筑具有指导意义。(4)充分考虑公路地基承载力特点(柔性“基础”、荷载分布为梯形、强度因固结增长),通过理论推导,获得了中低填土高度路堤下软土地基承载力增长计算理论公式,为计算路堤下软土地基承载力及其增长、推算各阶段路堤填筑安全高度提供了一种有效方法。(5)应用本文提出的软土地基承载力计算公式,计算了具有不同初始抗剪强度参数粘聚力和内摩擦角的软土地基在不同的固结度下的地基承载力值。基于计算结果,编制了软土抗剪强度参数随固结度增长的实用化表格,便于设计时使用。(6)考虑软土地基强度随时间(固结度)的增长,将路基稳定性分析和沉降计算有机结合起来,较好地克服了以往路基稳定性分析和沉降计算“隔离”分析的缺点,提出了基于强度增长理论的,能综合考虑稳定性和工后沉降的路基动态施工控制计算方法,并编制了计算机应用程序。更多还原

【Abstract】 Stability and deformation are two major problems in constructing buildings on soft ground. And Soft soil strength is a decisive factor in stabilizing soft ground. Soft soil strength increasing with the drainage consolidation is one of the important engineering characteristics. It is very important for soft ground of the low bearing capacity to increasing strength. To Master growing rule of strength is the foundation of reasonable controlling embankment filling velocity on soft soil, shortening the construction period and getting more scientific and more economical embankment filling method. Combined with communications science and technology project in Hunan and basis of researches at home and abroad, a number of exploration on the growth mechanism of soft ground strength, calculation method and engineering applications have been carried out relying on in-situ test of soft ground of expressway in Hunan, indoor and outdoor tests on soft soil strength parameters and theoretical analysis. The research results are as follows:(1) Systematically carried out three kinds of in-situ test on strength of soft soil foundation between mountains in Hunan. Regression equation of the cross plate shear strength (Cu) and light sounding test blow count (N10) was established. Those test research fruit laid the foundation for soft soil strength analysis of in-situ tests in test area.(2) Large amounts of physical and mechanics parameters test were carried out. Regression equation of parameters individuals and laboratory test index and in-sute test index based on test data. Factors influencing the bearing capacity of soft soil foundation is studied by means of grey relational analysis. Test fruit can heip to master the engineering characteristic of soft soil between mountains.(3) The consolidation tests and direct shear tests of soft soil were performed. The law of shear strength index of soft soil change with its degree of consolidation under different consolidation was studied. The affection of loading method, namely, one time loading and the stepped loading on thelaw of shear strengthwas researched. The relationships between degree consolidation and index of shear strength were recommended. The result can be referenced to the fill construction of embankment on soft soil.(4) Fully considering bearing capacity characteristics of the basement (flexible foundation, trapezoidal load distribution and strength increase due to consolidation), through theoretical derivation, calculation theoretical formulas of bearing capacity of low fill soft soil foundation was achieved. A new method was presented for assessing the bearing capacity under embankment at construction stage.(5)The formula is applied to calculate the increments of bearing capacity of soft soil foundation.Baesd on calculation results,a bearing capacity increasing calculation table was put forwads,which enhance the application value of the formula.(6) Considering soft soil foundation strength increasing with time (consolidation) and combining the stability analysis with settlement calculation organically to overcome the previous shortcomings; based on growth theory of strength, the research propose a dynamic control computing method of construction of embankment considering the stability and post-construction settlement and prepare the computer application program as well.更多还原