考虑孔隙比和渗透系数随应力变化的深基坑降水开挖分析

发布时间：2018-06-12 11:25

本文选题：渗透系数 + 深基坑　；参考：《广西大学》2015年硕士论文

【摘要】：针对土体渗透系数和孔隙比沿深度非线性变化且与土体的应力状态有关的实际情况,本文基于修正剑桥模型,建立了土体渗透系数与孔隙比、孔隙比与土体应力之间的函数关系,并利用ABAQUS及其二次开发平台,建立了考虑孔隙比和渗透系数随应力变化影响的深基坑降水开挖数值模型,并对深基坑降水开挖引起的支护结构内力、位移以及坑内外土体的位移展开了研究。主要研究内容和结果如下：(1)建立孔隙比随应力变化、渗透系数随孔隙比变化的函数关系,并编写了相应的用户子程序,建立了考虑孔隙比和渗透系数随应力变化影响的深基坑降水开挖数值模型。经验证发现该模型用于基坑降水开挖分析是合理可靠的。(2)在渗透系数不变的前提下,对比分析考虑与不考虑孔隙比变化结果发现,考虑孔隙比变化的墙体最大水平位移、地表最大沉降分别比后者大约28%、110%,深层土体沉降以及开挖深度以上的土体水平位移也比后者的明显较大,但最大坑底隆起比后者的小约31%。(3)在考虑孔隙比变化的前提下,对比分析考虑与不考虑渗透系数变化的结果发现,考虑渗透系数变化的墙体最大水平位移、最大地表沉降、坑底最大隆起、墙体最大弯矩(绝对值)分别比后者相应的结果小约30%、25%、10%、12%；前者的深层土体沉降以及开挖深度以上的土体水平位移比后者的明显较小。(4)对比分析同时考虑孔隙比和渗透系数变化与两者均不考虑的结果发现,同时考虑孔隙比和渗透系数变化的墙体最大水平位移、坑底最大隆起、墙体最大弯矩(绝对值)分别比两者均不考虑时相应的结果小约10%、38%、5%,但坑外土体沉降明显比后者的大。(5)深基坑降水开挖的数值模拟中考虑孔隙比和渗透系数随应力变化能较好地在反映降水的影响。可见,在深基坑降水开挖的数值模拟中考虑孔隙比和渗透系数随应力状态变化是很有必要的。
[Abstract]:In this paper, based on the modified Cambridge model, the permeability coefficient and porosity ratio of soil are established in view of the nonlinear variation of soil permeability coefficient and void ratio along the depth and related to the stress state of the soil. Based on the functional relationship between void ratio and soil stress and using Abaqus and its secondary development platform, a numerical model for dewatering excavation of deep foundation pit considering the effect of porosity ratio and permeability coefficient on stress is established. The internal force, displacement and the displacement of soil inside and outside the pit caused by dewatering excavation of deep foundation pit are studied. The main research contents and results are as follows: (1) the functional relationship of porosity ratio with stress and permeability coefficient with porosity ratio is established, and the corresponding user subprogram is written. A numerical model for dewatering excavation of deep foundation pit considering the effect of porosity ratio and permeability coefficient on stress is established. It is found that the model is reasonable and reliable for the analysis of dewatering and excavation of foundation pit. Under the premise of constant permeability coefficient, the maximum horizontal displacement of wall considering the variation of void ratio is found by comparing the analysis results with and without considering the variation of void ratio. The maximum settlement of the surface is about 28 / 110, respectively. The settlement of deep soil and the horizontal displacement of soil above the excavation depth are also significantly larger than those of the latter, but the maximum uplift of the bottom is about 31% smaller than that of the latter.) under the premise of considering the variation of porosity, By comparing the results of considering and disregarding the change of permeability coefficient, it is found that the maximum horizontal displacement, maximum surface settlement, maximum uplift of the bottom of the wall with the change of permeability coefficient are considered. The maximum bending moment (absolute value) of the wall is about 30% less than the corresponding result of the latter, respectively; the deep soil settlement of the former and the horizontal displacement of the soil above the excavation depth are obviously smaller than those of the latter) and the porosity ratio and permeability are taken into account simultaneously. The change of permeability coefficient and the result that neither of them were taken into account found that, At the same time, considering the change of porosity ratio and permeability coefficient, the maximum horizontal displacement of the wall and the maximum uplift of the bottom of the wall are taken into account. The maximum bending moment (absolute value) of the wall is about 100.38 and 55.But the settlement of soil outside the pit is obviously larger than that of the latter.) in the numerical simulation of dewatering excavation of deep foundation pit, porosity ratio and permeability coefficient are taken into account with stress. The change can better reflect the influence of precipitation. Therefore, it is necessary to consider the variation of void ratio and permeability coefficient with stress state in the numerical simulation of dewatering excavation of deep foundation pit.
【学位授予单位】：广西大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU463

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