考虑土体不均匀性的岩土工程可靠度分析

发布时间：2019-06-05 20:47

【摘要】：水利水电岩土工程包含多种不确定性因素,如岩土体参数不确定性、测量误差导致的认知不确定性和模型不确定性等,其中岩土体固有的不均匀性对岩土工程可靠度分析有重要的影响。由于土体普遍经历不同的地质、环境和化学作用,这导致不同深度的土体特性参数如抗剪强度参数往往呈现随深度变化的趋势,然而,目前大多数岩土工程可靠度分析虽然考虑了土性参数空间变异性的影响,但是土性参数随深度变化趋势对岩土结构物可靠度的影响还缺少深入的研究,如抗剪强度参数均值或标准差随深度变化对岩土结构物可靠度的影响规律等。另一方面,实际岩土工程中还存在另一种形式的岩土体不均匀性,即地层变异性。它表现为不同类型岩土材料的互相嵌套或一种类型土体材料在另一种较均质土体材料中不规则出现。这种地层变异性在其他领域如石油勘探、地下水及污染物运移研究中得到了足够的重视。岩土工程领域虽然很早就意识到地层变异性对岩土工程安全的影响,如有研究表明地层变异性对滑坡分布和方向有重要影响。然而,地层变异性对于岩土工程可靠度的影响还未见研究。此外,石油勘探,地下水污染物运移中都是采用基于大尺度分析的地层变异性模拟方法。对于大多数岩土结构物来说,这种地层变异性模拟方法不一定适用。因此,亟需发展适用于岩土结构物尺度的地层变异性模拟方法,在此基础上探讨地层变异性对岩土结构物可靠度的影响规律。此外,现有的考虑空间变异性的边坡可靠度分析大多关注边坡失效概率的计算,对于空间变异性对边坡失效模式的影响研究不够深入,而边坡最危险滑动面直接决定着边坡失稳的规模和尺寸,直接影响边坡失效后果评估。非常有必要深入研究土体参数空间变异性对边坡最危险滑动面分布规律的影响。针对上述3个关键科学问题,本文重点研究土体抗剪强度参数随深度变化的空间变异性和地层变异性模拟方法,在此基础上探讨这两种土体不均匀性对岩土结构物可靠度的影响规律,同时研究土体参数空间变异性对边坡最危险滑动面的影响。主要研究内容包括：基于非平稳随机场的土体抗剪强度参数空间变异性建模方法、土体空间变异性对边坡最危险滑动面的影响、考虑土体参数空间变异性的岩土结构物可靠度分析方法、基于钻孔资料的耦合马尔可夫链水平方向转移概率矩阵估计、考虑地层变异性的边坡稳定性分析方法。主要工作及结论如下：(1)阐述了考虑土体不均匀性的岩土工程可靠度分析的研究背景及意义,回顾了岩土参数不确定性的建模方法,指出了存在的问题和需要改进的方向。归纳了考虑参数空间变异性的岩土工程可靠度分析方法及研究对象。简要概述了地层变异性在岩土工程领域的研究现状,分析了考虑地层变异性的岩土工程可靠度关键问题,介绍了马尔可夫链模型在工程领域的应用情况。(2)为了研究抗剪强度参数随深度变化趋势对岩土结构物可靠度的影响,提出了表征抗剪强度参数空间变异性的非平稳随机场模型及其模拟方法。从经验公式和实测数据两方面验证了不排水抗剪强度参数和有效内摩擦角随土体深度变化的趋势,指出了两者非平稳随机场模型的差异,建立了不排水抗剪强度参数和有效内摩擦角的非平稳随机场模型,为利用总应力和有效应力方法考虑参数随深度变化趋势的空间变异性奠定了一定的理论基础。(3)针对考虑岩土体参数空间变异性的边坡最危险滑动面分布特征问题,提出了考虑土体抗剪强度参数空间变异性的边坡最危险滑动面确定方法,探讨了土体抗剪强度参数的波动范围和变异系数对边坡最危险滑动面分布规律的影响,揭示了抗剪强度参数空间变异性对边坡最危险滑动面位置、规模和分布范围的影响规律,为考虑土体参数空间变异性的边坡破坏模式确定提供了有效的分析工具。(4)提出了考虑土体抗剪强度参数均值随深度变化的无限长边坡稳定性概率分析方法,建立了表征土体抗剪强度参数空间变异性的非平稳随机场模型,探讨了考虑土体抗剪强度参数空间变异性时边坡失效概率和最危险滑动面的变化规律,以无限长不排水黏性土坡和摩擦/黏性土坡为例验证了所提方法的有效性,搜集了现实中实际滑坡案例验证了数值分析结果的正确性。研究成果为实际工程中大多数滑坡发生浅层破坏现象提供了有效依据。(5)提出了考虑土体不排水抗剪强度均值和标准差随深度变化的地基稳定性概率分析方法,阐明了土体不排水抗剪强度参数空间变异性对地基极限承载力的影响规律,系统地比较了不排水抗剪强度参数平稳和非平稳随机场模型对地基极限承载力的影响。得出了忽略不排水抗剪强度参数随深度变化趋势将会明显低估不排水条件下地基可靠度的重要结论,为改进地基可靠度设计提供了方向。(6)针对岩土结构物中地层变异性模拟问题,提出了一种新的耦合马尔可夫链水平方向转移概率矩阵估计方法,实现了岩土结构物地层变异性的精细模拟。搜集了不同地区的钻孔资料,检验了土体状态转移的一阶马尔可夫性,验证了所提方法的有效性。在此基础上,研究了土体状态转移马尔可夫链水平方向转移概率矩阵和竖直方向转移概率矩阵的一般规律,实现了土体状态转移水平方向转移概率矩阵的有效估计,为岩土工程中地层变异性的模拟奠定了理论基础。(7)提出了考虑地层变异性时边坡稳定安全系数分析方法,建立了基于钻孔资料和耦合马尔可夫链的地层变异性模型,基于有限元应力法建立了考虑地层变异性时边坡稳定性概率分析方法。分析了不同钻孔布置方案对边坡稳定安全系数不确定性的影响,建议了最外围钻孔距边坡坡顶(或坡脚)的合适距离,阐明了钻孔位置、数目对边坡稳定安全系数和最危险滑动面不确定性的影响规律,为地质勘探方案设计提供了理论指导。
[Abstract]:The geotechnical engineering of water and water resources has many uncertainties, such as the uncertainty of the parameters of the rock and soil body, the cognitive uncertainty and the model uncertainty caused by the measurement error, etc., in which the inherent non-uniformity of the rock and soil body has an important influence on the reliability analysis of the geotechnical engineering. due to the different geological, environmental and chemical effects of the soil body, the soil property parameters such as shear strength parameters of different depths tend to exhibit a tendency to change with depth, however, At present, the reliability analysis of most geotechnical engineering has taken into account the influence of the spatial variability of the soil parameters, but the influence of the soil property parameters with the depth change trend on the reliability of the soil structure is still lacking. Such as the influence of the mean or standard deviation of the shear strength parameter on the reliability of the rock and soil structure with the depth change, and the like. On the other hand, there is another form of heterogeneity of the rock and soil in the practical geotechnical engineering, that is, the formation variability. It shows that the internesting of different types of rock and soil materials or one type of soil material is irregular in another relatively homogeneous soil material. Such formation variability has been given sufficient attention in other fields, such as oil exploration, groundwater and pollutant migration. Although the geotechnical engineering field has long been aware of the effect of formation variability on the safety of the geotechnical engineering, the study indicates that the formation variability has an important effect on the distribution and direction of the landslide. However, the effect of formation variability on the reliability of geotechnical engineering is not shown in the study. In addition, the formation variability simulation method based on large-scale analysis is adopted in the migration of oil and groundwater pollutants. For most rock-and-soil structures, this method of formation variability is not necessarily applicable. Therefore, it is urgent to develop a method for simulating the formation variability applicable to the scale of the rock and soil structure, and on this basis, the effect of formation variability on the reliability of the rock and soil structure is discussed. In addition, the existing slope reliability analysis considering the spatial variability is mostly concerned with the calculation of the failure probability of the slope, the influence of the spatial variability on the failure mode of the slope is not deep enough, and the most dangerous sliding surface of the slope directly determines the scale and the size of the slope failure, And directly influence the slope failure consequence assessment. It is necessary to study the effect of the spatial variability of soil parameters on the distribution of the most dangerous sliding surface of the slope. In view of the above three key scientific problems, this paper focuses on the spatial variability of the soil shear strength parameter with depth and the simulation method of the formation variability, and on the basis of this, the influence of the non-uniformity of the two soils on the reliability of the soil structure is discussed. The effect of the spatial variability of the soil parameters on the most dangerous sliding surface of the slope is also studied. The main research contents include the method of modeling the spatial variability of the shear strength of the soil in the non-stationary random field, the influence of the soil spatial variability on the most dangerous sliding surface of the slope, and the reliability analysis method of the soil-soil structure considering the spatial variability of the soil parameters, The method of slope stability analysis considering the formation variability is given based on the estimation of the probability matrix of the horizontal transfer probability of the coupled Markov chain based on the drilling data. The main work and conclusions are as follows: (1) The research background and significance of the reliability analysis of the geotechnical engineering considering the non-uniformity of the soil body are described, the modeling method of the uncertainty of the geotechnical parameters is reviewed, and the existing problems and the direction to be improved are pointed out. The reliability analysis method and the research object of the geotechnical engineering considering the spatial variability of the parameters are summarized. The present situation of the formation variability in the field of geotechnical engineering is briefly introduced, and the key problem of the reliability of the geotechnical engineering considering the formation variability is analyzed, and the application of the Markov chain model in the field of engineering is introduced. (2) In order to study the effect of the variation trend of shear strength on the reliability of the rock and soil structure, the non-stationary random field model and its simulation method to characterize the spatial variability of the shear strength parameter are put forward. The trend of the non-drained shear strength and the effective internal friction angle with the depth of the soil is verified from the empirical formula and the measured data, and the non-stationary random field model of the non-drained shear strength parameter and the effective internal friction angle is established by the difference between the non-smooth shear strength parameters and the effective internal friction angle. In order to use the total stress and effective stress method to consider the spatial variability of the parameters with the depth trend, a certain theoretical foundation is laid. (3) The method for determining the most dangerous sliding surface of the side slope considering the spatial variability of the shear strength of the soil is proposed in view of the problem of the distribution of the most dangerous sliding surface of the side slope considering the spatial variability of the rock and soil parameters. The influence of the fluctuation range and coefficient of variation of the shear strength parameter of soil on the distribution of the most dangerous sliding surface of the slope is discussed, and the influence of the spatial variability of the shear strength parameter on the position, scale and distribution of the most dangerous sliding surface of the slope is revealed. An effective analytical tool is provided to determine the slope failure mode of the spatial variability of soil parameters. (4) An infinite long slope stability probability analysis method considering the variation of the mean value of the shear strength of the soil body with the depth is put forward, and a non-stationary random field model for characterizing the spatial variability of the shear strength parameter of the soil body is established, The change law of slope failure probability and the most dangerous sliding surface in consideration of the spatial variability of the shear strength of the soil is discussed, and the effectiveness of the proposed method is verified by taking an infinite long non-drainage cohesive soil slope and a friction/ cohesive soil slope as an example. The correctness of the results of the numerical analysis is verified by the actual landslide case in the real world. The research results provide an effective basis for the occurrence of shallow damage in most landslides in the actual project. (5) The method of foundation stability probability analysis considering the mean and standard deviation of the non-drained shear strength of the soil and the variation of the standard deviation with the depth is put forward, and the influence of the spatial variability of the non-drainage shear strength of the soil on the ultimate bearing capacity of the foundation is clarified. The effect of undrained shear strength parameters on the ultimate bearing capacity of the foundation is systematically compared. It is concluded that ignoring the variation trend of the non-drained shear strength parameter with the depth will significantly undervalue the reliability of the foundation under the undrained condition, and provides a direction for improving the reliability design of the foundation. (6) In order to simulate the formation variability in the rock and soil structure, a new method for estimating the horizontal transfer probability matrix of the coupled Markov chain is proposed, and the fine simulation of the formation variability of the rock and soil structure is realized. The first-order Markov property of the state transition of the soil is checked, and the validity of the proposed method is verified. On the basis of this, the general rule of the transition probability matrix and the vertical direction transfer probability matrix of the state transition Markov chain of the soil is studied, and the effective estimation of the transfer probability matrix in the horizontal direction of the state of the soil is realized. It lays a theoretical foundation for the simulation of formation variability in geotechnical engineering. (7) The method of slope stability safety factor analysis based on borehole data and coupled Markov chain is put forward, and the method of slope stability probability analysis is established based on the finite element stress method. The influence of different drilling arrangement schemes on the uncertainty of the safety factor of the slope stability is analyzed, and the appropriate distance between the most peripheral drilling hole and the slope top (or toe) of the slope is proposed, the influence of the drilling position, the number of the number on the stability safety factor of the slope and the uncertainty of the most dangerous sliding surface is clarified. It provides the theoretical guidance for the design of geological exploration.
【学位授予单位】：武汉大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TV223

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