基于可靠性理论的深基坑支护稳定性验算方法研究

发布时间：2018-03-19 12:21

  本文选题：深基坑　切入点：双排桩　出处：《中国地质大学(北京)》2017年硕士论文　论文类型：学位论文

【摘要】：随着城市建设的推进与深基坑工程向纵深发展,新的支护形式不断涌现。双排桩支护方法因其在复杂工程条件下较好的适用性得到广泛的应用和认可,已经成为基坑支护的重要方法之一。考虑到目前基坑支护理论研究落后于工程实践的现状,以及深基坑工程事故频发、支护设计过于保守造成浪费等现象,本文针对深基坑支护稳定性的理论及验证方法进行了进一步探索。本文主要的研究内容及分析结果如下:(1)对工程现场勘察资料进行整理,根据勘察结果区分土层,并进行各参数数据分类统计,根据统计结果描绘出各参数的分布规律,研究发现对于不同土层中的粘聚力、内摩擦角和重度均大致复合正态分布规律;(2)建立了深基坑双排桩支护的FLAC3D数值计算模型,根据实际工程状况确定模型的边界条件、初始条件与模型参数,合理布置支护桩,分步开挖计算。计算结果表明:在现场工况下进行双排桩支护,基坑开挖后可以最终达到稳定状态;基坑开挖后主应力迹线及大小均会发生变化,坡脚应力集中明显;越靠近开挖面顶部水平位移越大,竖向最大位移发生在距坡面一定距离处;排桩可改善周围区域土体的应力状况,制约土体变形;后排桩的支护效果大于前排桩;(3)根据数值计算结果图像确定出基坑坡后土体的可能滑动面,对滑动面曲线进行拟合并确定其数学表达式,根据条分法给出了计算坡后土体抗滑稳定性的公式;(4)采用Monte-Carlo可靠性方法,以输入参数的概率分布为基础,建立起分析基坑失效概率的计算模型并编制相应计算程序。将实际工况下的大量计算结果进行统计分析发现:由稳定性计算公式得到的大量计算值的概率密度大致服从正态分布;由累积概率曲线可知,该工况下基坑土体达到抗滑稳定的概率为98%,支护满足安全要求;(5)通过对不同土层、各个参数对计算结果的影响研究发现:各个参数中内摩擦角对土体稳定性的影响最大;不同土层各参数对稳定性的影响不同,其中粉质黏土影响要大于淤泥质黏土;土的重度对计算结果影响不大。
[Abstract]:With the advance of urban construction and the development of deep foundation pit engineering, new support forms are emerging constantly. The double row pile support method has been widely used and approved because of its good applicability in complex engineering conditions. It has become one of the important methods of foundation pit support. Considering the fact that the research of foundation pit support theory lags behind the engineering practice at present, and the accidents of deep foundation pit engineering occur frequently, the support design is too conservative and causes waste, etc. In this paper, the theory and verification method of supporting stability of deep foundation pit are further explored. The main research contents and analysis results of this paper are as follows: 1. According to the statistical results, the distribution law of each parameter is described, and the cohesive force in different soil layers is found. The FLAC3D numerical calculation model of double-row pile support in deep foundation pit is established. The boundary conditions, initial conditions and model parameters of the model are determined according to the actual engineering conditions, and the supporting piles are reasonably arranged. The calculation results show that the stability of foundation pit can be achieved after excavation, the main stress trace and size will change after excavation, and the stress concentration of slope foot will be obvious. The bigger the horizontal displacement is near the top of the excavated surface, the greater the vertical maximum displacement occurs at a certain distance from the slope surface, and the pile row can improve the stress condition of soil in the surrounding area and restrict the deformation of soil. The supporting effect of the back row pile is better than that of the front row pile. According to the image of the numerical calculation results, the possible sliding surface of the soil after the foundation pit slope is determined, and the mathematical expression of the sliding surface curve is determined by the pseudo combination of the sliding surface curve. According to the slice method, the formula for calculating the anti-slide stability of soil after slope is given. The Monte-Carlo reliability method is adopted, and the probability distribution of input parameters is used as the basis. The calculation model of the failure probability of foundation pit is established and the corresponding calculation program is worked out. It is found that the probability density of a large number of calculated values obtained from the formula of stability calculation is large by statistical analysis of a large number of calculation results under actual working conditions. Induced by the normal distribution; According to the cumulative probability curve, the probability of the stability of foundation pit soil is 98 and the support meets the safety requirements. The results show that the internal friction angle has the greatest influence on the stability of soil, and the influence of different soil layer parameters on soil stability is different, and the influence of silt clay is greater than that of silt clay. The weight of soil has little effect on the calculation results.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU753
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本文编号：1634245