【作者】 金小荣；

【导师】 龚晓南； 俞建霖；

【作者基本信息】 浙江大学 ， 岩土工程， 2007， 博士

【摘要】 真空预压法及真空联合堆载预压法作为一种较为有效的软土地基处理方法，具有诸多优点。近年来，该法在码头堆场、机场、发电厂、高速公路和高等级公路桥头段等软基处理中得到广泛应用。真空预压法及真空联合堆载预压法在机理研究、施工工艺、设计理论等方面已取得了长足进步，但理论研究仍落后于工程实践。目前尚存在一些学术界和工程界较为关心的理论问题急需解决，如真空预压和堆载预压加固效果的差别、真空预压法是否适合加固下卧承压水的软弱地基、真空预压加固区地下水位的变化规律、真空联合堆载预压的稳定问题、真空预压的环境效应及其防治方法研究等问题，因此制约了该工法的进一步推广和应用，已引起国内外学术界和工程界的广泛关注。本文在前人工作的基础上，通过室内试验、现场试验和理论研究，对真空联合堆载预压的加固机理与若干理论进行了探讨。 本文的主要工作有： 1、基于改进的Rowe型固结仪，进行了真空预压、堆载预压和真空联合堆载预压试验。 2、结合220kV港湾变现场试验对真空联合堆载预压法加固下伏承压水软基进行了研究。现场试验表明：撕膜与非撕膜的塑排板施工工艺能有效防止承压水贯通，真空联合堆载预压能有效消除下伏承压水层软弱地基的沉降，加固后地基平均固结度已达83％，工后沉降较小。 3、根据固结度等效的原则，提出了基于双指数衰减的负压分布模式的砂井地基等效公式，可用于平面应变有限元计算。同时在前人研究真空预压加固地基解析理论成果的基础上，推导了下伏承压水软基真空预压加固地基的解析解。 4、运用ABAQUS有限元程序，对真空联合堆载预压加固软基的稳定性进行了研究；数值分析表明真空联合堆载预压的稳定性状受真空度大小、加固深度、土体强度和加载曲线等因素影响。结合两个失稳的真空联合堆载预压工程实例，采用数值方法对其进行模拟，并提出防止失稳的几点建议。 5、研究了真空预压的环境效应，重点研究了真空预压对周围管线的影响，同时提出减小真空预压不利影响的三个防治方法。 6、结合工程实践和近年来真空预压相关工艺的发展，对现有施工工法提出一些改进措施，进一步完善了真空预压法的施工工艺。更多还原

【Abstract】 Vacuum preloading and vacuum-surcharge preloading are effective methods to improve soft foundation.In recent years, these method was extensively used to treat soft clay ground such as harbor yard,airport,electric power plant,express highway, highway at bridge-head and etc.There have been great deep developments of improvement mechanism,construction techniques and design theory, whereas the development of theory for vacuum preloading and vacuum-surcharge preloading has lagged hehind a lot the engineering practice. Many problems such as the difference between vacuum preloading and surcharge preloading, the feasibility of soft clay with confined water by vacuum preloading,the rule of underground water during vacuum preloading, the stabibility of vacuum-surcharge preloading,the environment effect of vacuum preloading, its control method and etc still exist.This status has limited the more and more application and development of these two methods,which largely provokes more both academic and engineering researchers at home and abroad.Based on the former researchers’ achievement, this dissertation focused on the mechanism and theory of vacuum preloading and vacuum-surcharge preloading through laboratory test,field experiment and theoretical study. The main aspects of this dissertation were studied as follows:1. Based on the improved Rowe’s consolidation apparatus, the laboratory tests of vacuum preloading, surcharge preloading and vacuum-surcharge preloading were conducted.2. Field experiment of soft ground with confined water at Gangwan 220kV was performed. The results showed that it’s safe and economic that the technology of ’tearing membrane’ was combined with the ’non-tearing membrane’ while driving PVDs.The main settlements could be eliminated effectively by vacuum-surcharge preloading at soft foundation with confined water, the degree of consolidation of total soft soil was 83% and that prediction post-construction which would last for more than 100 years was acceptable.3. According to the principle of equality of degree of consolidation, based on the negative pressure distribution pattern of twice exponential decay, the formula of equality for sand drains was deduced.The solutions about soft foundation with confined water by vacuum preloading and vacuum-surcharge preloading were derived from the previous research of other people.4. With ABAQUS FEA program, the stability of soft soil foundation treated with vacuum-surcharge preloading was studied.The results showed that the stability of soft soil foundation was related to the degree of vacuum, the depth of treatment,更多还原