【作者】 王坤；

【导师】 黄涛；

【作者基本信息】 西南交通大学 ， 工程环境控制， 2010， 硕士

【摘要】 在含水量丰富的软土地区进行基坑工程开挖,不可避免地要遇到地下水问题。地下水位的变化引发土体中渗流场和应力场的改变,研究地下水与土体相互作用的机理以及渗流作用对基坑工程的影响,获得地下水位变化后土体结构变化的详细数据,是具有重要的理论研究价值和工程应用价值的。本文以天津地区具体工程为实例研究了地下水对深基坑开挖的影响。本文首先对天津地区的水文地质条件进行了综合评价。对天津地区地层成因及岩性进行了分析,研究了地下水的成因及赋存状况。并对地下水与外界水体的水力联系以及地下水体各含水层之间的水力联系做了分析,得到了地下水的运移规律。通过水文地质实验,对各含水层的渗透性做了分析。为后续研究打下了基础。其次,综合分析了地下水影响下容易产生的各类地质灾害。对深基坑底板的抗浮特性做了研究,分析了基坑底板浮托作用机制并提出了坑底抗浮的相关工程措施。分析了管涌、突涌、流土(砂)等地质灾害的产生机制,提出了量化的预测公式,并针对各类地质灾害提出了工程对策。在水文地质条件综合评价的基础上,以达西定律、裘布依假设和有效应力原理为基础,对渗流场-应力场之间的耦合作用机制做了理论分析,建立了渗流-应力耦合模型。最后,以天津地铁二号线具体工程为实例,由COMSOL Multiphysics软件计算了渗流场和应力场之间的相互作用关系,得到了水头下降后土体孔隙率、沉降量之间的具体数值关系,并获得由土体结构改变对渗透系数影响的具体关系。为基坑降水设计提供了理论依据。本文工作对于深基坑降水设计、施工具有一定的参考价值。更多还原

【Abstract】 The problems caused by ground water are unavoidable during the excavation of foundation pit engineering in soft fields containing plenty of ground water. The seepage field and the stress field will be changed as the ground water level changes. Therefore, it would be of great theoretical value as well as engineering practice value to study the manual interaction mechanism between ground water and soils and the impact of seepage function on the foundation engineering, and obtain the specific data of the changes of soil structure as the ground water level changes. This thesis studies the impact of ground water on the excavation of foundation pit based on a certain engineering in Tianjin area.Firstly, the hydrogeological conditions of Tianjin area are comprehensively evaluated. Through analyzing the formation of the stratum and the lithology, the formation and status of ground water is studied. The motion characteristic of the ground water is obtained based on the analysis of the hydrodynamic connection between each aquifers and the ground water and the ambient water, which lays the foundation of the afterwards studies.Secondly, different kinds of geologic hazards caused by ground water are synthetically analyzed. This thesis studied the resisting of uplift effect of the pit bottom, and analyzed the mechanism of uplift effect, based on which, the corresponding countermeasures are brought up. Also, the mechanism of piping, surging and soil flowing are studied, and the numerical prediction equations are established, at last, the countermeasures for each geologic hazards are brought up.Based on the synthetic analysis of hydrogeological conditions, this thesis studied the coupling effect mechanism between seepage field and stress field according to Darcy’s Law, Dupuit Hypothesis and The Principle of Effective Stress, and established the coupling model of seepage and stress.At last, this thesis took the specific engineering of the second line of Tianjin metro as an example, calculated the interaction connection between the seepage field and the stress field, and achieved the numerical relevance of the void ratio and the settlement as the ground water level descends, furthermore, the specific relevance between the permeability coefficient and the soil structure are obtained.The study based on this thesis provides valuable instructions for the designing, construction of the dewatering excavation.更多还原