【作者】 罗戌；

【导师】 顾长存；

【作者基本信息】 河海大学 ， 岩土工程， 2005， 硕士

【摘要】 真空联合堆载预压法是一种较为有效的软基处理方法，可以很好地解决软基的沉降和稳定问题，并能缩短工期。该法广泛应用于高速公路、港口、码头等工程建设中，取得了良好的加固效果，但是在加固机理研究方面还存在许多问题，制约了该法的进一步推广和应用。 本文在前人研究成果的基础上，结合大量的试验资料，通过理论分析和数学计算，对真空联合堆载预压法加固软基过程中，地下水位、真空度、孔隙水压力及土体抗剪强度等的变化规律进行了深入研究。主要完成了以下几方面的工作： (1) 利用渗流量数学计算模型，求出砂井渗流量、竖向渗流量和加固区外渗流量，根据地下水动力学相关理论计算水位降深，并分析了渗流量、水位降深随时间的变化规律及渗流量与水位降深之间的关系。结合加固区内利用水位管观测地下水位的工作原理，分析常用地下水位观测方法存在的弊端，并提出改进方法。 (2) 利用水位变化研究成果，结合现场实测资料，深入研究了水位变化对真空度、孔隙水压力等的影响，并对工程上“真空度”的含义提出新的解释，同时提出“真空吸力”、“真空能量”及“真空度有效传递深度”的概念。从土体微观变化的角度入手，结合真空联合预压的加固机理，分析了加载过程中孔压变化滞后的原因。 (3) 从土体微观变形的角度入手，结合真空联合堆载预压的加固机理，分析抽真空过程中土体饱和度变化规律，得出抽真空过程中地下水位降落区内可能形成非饱和区的结论，同时分析了地下水位降落区变成非饱和的前提条件。 (4) 分析硬壳层的形成机理，通过计算分析硬壳层的存在对地基沉降变形的影响。更多还原

【Abstract】 Vacuum combined surcharge preloading is a more effective soft-foundation improvement method. The settlement and stability problems are well solved by this method, and the time limit for a project is shortened. Now, this soft-foundation improvement method is widely used in several kinds of civil engineering projects, such as express highway, port, wharf and so on, and favorable effect is obtained. However, there are still many problems on the research of improvement mechanism. These problems have restricted its wide application. Based on former research and plentiful experimental data, the change laws of underground water level, vacuum degree, pore-water pressure and soil shear strength during reinforcing are deeply researched by theoretically analyzing and numerically calculating. The main works in this paper are listed as follow:Firstly, mathematical calculation model of seepage discharge is used, and the quantity of percolation of drain pile, vertical seepage and the infiltration from the area outside reinforced zone are calculated. According the correlative theories of underground water dynamics, the depth of groundwater is confirmed. The relation between seepage discharge and groundwater level and the change laws of the quantity of percolation and groundwater level are analyzed. According to the work principle of water level gauge and the observation method through water level pile, the disadvantages of traditional observation method of groundwater level are analyzed, and the amelioration method is put forward.Secondly, based on the researching results of groundwater level change laws and local observation data, the effect on vacuum degree and pore-water pressure with the change of groundwater level are deeply studied. New explanation of vacuum degree, and the concept of vacuum suction and the effective transferring depth of vacuum degree are brought forward. According to the reinforcement mechanism of vacuum combined surcharge preloading, the reasons of the change time of pore-water pressure lagging behind loading time are analyzed.Thirdly, according to the reinforcement mechanism of vacuum combined surcharge preloading, analyzing the change laws of soil saturation degree, and drawing a conclusion that it is possible to change into unsarurated in the groundwater level descendent area during vacuumizing. At the same time, the preconditions are confirmed.Fourthly, the formation principle of hard crust during vacuumizing is analyzed. The effect on foundation settlement deformation of this hard crust is analyzed by numerical calculation.更多还原