基坑降水对支护结构及土体变形影响因素的数值分析

发布时间：2018-03-18 02:28

本文选题：FLAC3D4.0　切入点：基坑降水　出处：《太原理工大学》2013年硕士论文　论文类型：学位论文

【摘要】：随着城市密度的逐步增大,建筑物之间的间距已经缩小至极限,这就提高了对基坑支护的有关要求。对基坑周边建筑物的沉降及控制基坑的水平位移也相应的提出了挑战。另外,基坑降水可能引起的土体沉降及支护结构的变形随着不同土层的渗透系数的不同自然也有差异。所以对于基坑支护及降水所引起的沉降的影响因素很多,甚至于这些因素之间的相互作用,都可能在对周边沉降控制比较严格的基坑或者开挖比较深的基坑的沉降控制中起着至关重要的作用,如何能够在支护及降水中将这些因素考虑的比较全面及合理,是一个亟待研究和解决的问题。为了研究降水过程中各种参数对周边土体的沉降及水平位移的影响,本文对基坑降水,土体的变形以及对支护结构的变形的理论研究进行了详细阐述,并采用FLAC3D4.0建模,同时采用其含有的渗流模块的模式进行计算,对降水及开挖引起的周边土体的沉降及支护结构的变形进行了研究与分析,得出了有关参数的影响作用的大小。 (1)本文通过改变基坑支护结构地下连续墙的模量,改变基坑支护结构内外的水头差及基坑支护结构中的支撑的位置,分别分析了降水及开挖过程中各个参数对连续墙的弯矩,周边土体的竖向及侧向变形,支撑的轴力的影响。 (2)本文还对FLAC3D中的摩尔库仑模型及Cysoil模型的计算结果进行了对比,得出两种模型的计算结果的差异及应用效果。根据上述的分析得出结论： (1)M-C模型与C-Y模型相比,弯矩和撑力相差不大,在10%～25%左右,变形值相差较大,沉降C-Y模型的值大,水平位移M-C模型的值大,回弹M-C模型的值大。 (2)当连续墙模量改变时,墙的弯矩随模量增大而增大,沉降和水平位移随模量的增大而减小,总撑力几乎不变。 (3)随着坑外水位的降低,连续墙的弯矩和支撑轴力都会大幅度下降,水平位移和地表沉降也都大幅下降。 (4)随着土体的模量的增加,墙体弯矩和变形都相应减小,土体模量增大3倍,弯矩下降15%,沉降减小30%,水平位移减小25%,支撑轴力变化不大。 (5)改变支撑位置可以优化连续墙和支撑的轴力,增加一道支撑可以显著降低连续墙的弯矩和基坑的变形。 (6)坑外动水压力小于降水压力,坑内的动水压力大于降水压力,坑内动水压力会减小土体的有效应力,增加坑底隆起风险,抗渗流和抗隆起是相互关联的。
[Abstract]:As the density of cities increases, the spacing between buildings has narrowed to the limit. This raises the requirements for foundation pit support. It also challenges the settlement of buildings around the foundation pit and the control of the horizontal displacement of the foundation pit. In addition, The settlement of soil and the deformation of supporting structure caused by dewatering of foundation pit are different naturally with the different permeability coefficient of different soil layers, so there are many factors that affect the settlement caused by foundation pit support and dewatering. Even the interaction of these factors may play an important role in the settlement control of the foundation pit with strict control of the peripheral settlement or the settlement control of the deeper foundation pit. How to consider these factors comprehensively and reasonably in support and precipitation is an urgent problem to be studied and solved. In order to study the influence of various parameters on the settlement and horizontal displacement of surrounding soil in the process of dewatering, the theoretical study of foundation pit dewatering, deformation of soil and deformation of supporting structure is described in detail in this paper, and the FLAC3D4.0 model is used. At the same time, by using the model of seepage module, the settlement of surrounding soil and the deformation of supporting structure caused by precipitation and excavation are studied and analyzed, and the effect of relevant parameters is obtained. 1) by changing the modulus of underground continuous wall of foundation pit support structure, changing the water head difference inside and outside of foundation pit support structure and the position of support in foundation pit supporting structure, the paper analyzes the dewatering and the bending moment of each parameter to continuous wall during excavation, respectively. The vertical and lateral deformation of the surrounding soil and the influence of the axial force of the bracing. 2) in this paper, we also compare the calculation results of the Moore Coulomb model and the Cysoil model in FLAC3D, and get the difference between the results of the two models and their application results. On the basis of the above analysis, it is concluded that:. Compared with the C-Y model, the bending moment and bracing force of the M-C model are not different from those of the C-Y model. The deformation value of the model is about 25%, the value of the settlement C-Y model is large, the value of the horizontal displacement M-C model is large, and the value of the springback M-C model is larger than that of the horizontal displacement M-C model. 2) when the modulus of the continuous wall is changed, the bending moment of the wall increases with the increase of the modulus, the settlement and horizontal displacement decrease with the increase of the modulus, and the total supporting force is almost unchanged. 3) with the decrease of the water level outside the pit, the bending moment and the supporting axial force of the continuous wall will be greatly reduced, and the horizontal displacement and the surface subsidence will also be reduced significantly. 4) with the increase of soil modulus, the bending moment and deformation of the wall decrease accordingly, the modulus of the soil increases by 3 times, the bending moment decreases by 15 times, the settlement decreases by 30%, the horizontal displacement decreases by 25%, and the axial force of the support does not change much. 5) the axial force of continuous wall and bracing can be optimized by changing the position of bracing, and the bending moment of continuous wall and deformation of foundation pit can be significantly reduced by adding one bracing. 6) the dynamic water pressure outside the pit is less than the precipitation pressure, and the dynamic water pressure in the pit is greater than the precipitation pressure. The dynamic water pressure in the pit will reduce the effective stress of soil and increase the risk of uplift at the bottom of the pit. The anti-seepage flow and the anti-uplift are interrelated.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU46

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