软土地区基于流固耦合理论的基坑变形分析

发布时间：2019-03-16 14:30

【摘要】：近年来,国内外岩土工作者对基坑工程的研究取得了很多的优秀成果,在基坑的设计、施工上也积累了许多可借鉴的经验。随着城市现代化的加速发展,城市的高层及地下建筑物不断增加,随之对基坑稳定性及变形的要求也越来越高。特别是在沿海软土地区,需要采取有效的措施减少这种复杂的地质条件对基坑稳定性及变形的影响。在软土地区一个很显著的问题就是地下水的问题,在基坑开挖过程中当开挖面在地下水位以下时需要进行基坑降水,地下水水位的变化引发土体渗流场和应力场的改变,且渗流场与应力场的相互作用,会对基坑变形及围护结构内力产生影响。因而,研究基坑渗流场与应力场耦合作用具有重要的理论研究价值和工程应用价值的。本文以软土地区基坑工程为实例,分别采用MC模型、HS模型对其进行有限元模拟,分析得到用HS模型得出的结果更接近于实际情况,所以在模拟软土地区基坑开挖过程选用HS本构模型较为适合。借助苏州狮山科技馆基坑工程实例对其降水开挖过程进行数值模拟。结合渗流场、应力场的耦合方程,利用数值软件PLAXIS建立两个基坑模型,一个是基于总应力法不考虑水影响的模型,另一个是基于有效应力法考虑基坑降水的流固耦合模型。对墙体位移、基底隆起值、地表沉降及墙体内力值进行对比分析,得出考虑耦合作用下的基坑变形及内力均大于不考虑耦合作用的结果,且耦合作用下的基坑位移与实际监测数据较接近,提出在软土地区进行基坑开挖降水需要考虑耦合作用的影响。同时,分析了降水深度、嵌固深度对坑外土体沉降产生的影响,加大嵌固深度会减小坑外土体的沉降,降水深度的增加会加大坑外土体的沉降。
[Abstract]:In recent years, the research on the foundation pit engineering of the geotechnical workers at home and abroad has obtained many excellent results, and many valuable experiences have been accumulated in the design and construction of the foundation pit. With the rapid development of the city's modernization, the high-rise and underground structures of the city are increasing, and the requirements for the stability and deformation of the foundation pit are also higher and higher. In particular, in the coastal soft soil area, effective measures are needed to reduce the influence of such complicated geological conditions on the stability and deformation of the foundation pit. a very significant problem in the soft soil area is the problem of the underground water, when the excavation surface is below the ground water level during the excavation of the foundation pit, the dewatering of the foundation pit is required, the change of the water level of the underground water causes the change of the seepage field and the stress field of the soil body, and the interaction of the seepage field and the stress field, The deformation of the foundation pit and the internal force of the enclosing structure can be affected. Therefore, the study of the coupling between the seepage field and the stress field of the foundation pit is of great theoretical research value and engineering application value. In this paper, based on the case of the foundation pit in soft soil area, the MC model and the HS model are used to simulate the foundation pit in the soft soil area, and the results obtained by the HS model are closer to the actual conditions, so the HS constitutive model is suitable for the excavation of the foundation pit in the soft soil area. The numerical simulation of the precipitation excavation process is carried out with the help of the project of the foundation pit of Shishan Science and Technology Museum in Suzhou. Combined with the coupling equation of the seepage field and the stress field, two foundation pit models are established by the numerical software PLAXIS, one is the model which is based on the total stress method and does not consider the influence of water, and the other is a fluid-solid coupling model considering the dewatering of the foundation pit based on the effective stress method. The displacement of the wall, the uplift of the base, the surface settlement and the internal force of the wall are compared and analyzed, and the result that the deformation and internal force of the foundation pit under the coupling action is greater than that of the coupling action is not considered, and the displacement of the foundation pit under the coupling action is close to the actual monitoring data, It is suggested that the effect of coupling effect should be considered in the excavation and precipitation of foundation pit in soft soil area. At the same time, the influence of the depth of the precipitation and the depth of the embedded solid on the settlement of the soil in the outside of the pit is analyzed, the settlement of the soil outside the pit can be reduced, and the increase of the depth of the precipitation will increase the settlement of the soil outside the pit.
【学位授予单位】：石家庄经济学院
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU753

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