考虑基本变量互相关性及自相关性的非饱和土地基基础可靠度研究

There are various uncertainties and correlations in foundation engineering in unsaturated soils, so it is necessary to adopt reliability method to analyze their effects on the stability and deformation of foundation engineering. Through physical properties tests, mechanical properties tests, hydraulic properties tests, pore size distribution tests, grain size distribution tests and loading tests, the probabilistic statistical characteristics of unsaturated soils’ properties and model factors are obtained, and a finite element method is proposed to analyze the spatial variability of unsaturated soils. Considering the saturated-unsaturated seepage and fluid-structure interaction, a deterministic numerical model for foundation engineering in unsaturated soils is built. Considering the cross-correlation, auto-correlation and non-normality of basic variables, a random response surface method (RSM) for the reliability analysis of foundation in unsaturated soils is proposed. Different criteria for judging the accuracy of a response surface method and different sampling strategies are presented for different types of response surfaces. Then, a system reliability analysis method and a sensitivity analysis method are put forward, and these methods can consider the cross-correlation, auto-correlation and non-normality of basic variables. Based on the above methods, reliability analysis and sensitivity analysis are carried out for the ultimate limit state (ULS), the service limit state (SLS) and the parallel system of ULS and SLS of foundation in unsaturated soils. According to the analysis, failure mechanism of foundation in unsaturated soils under special environmental conditions such as rainfall and variation of ground water levels are illuminated, the main influencing factors and their effects on the reliability of foundation in unsaturated soils are obtained. The research of this project can guide the stability evaluation and design of foundation engineering and other geotechnical engineering.

非饱和土地基基础工程存在多种不确定性及相关性，需要采用可靠度方法分析它们对基础工程稳定性及变形的影响。通过对非饱和细粒土进行物理性质、力学性质、水力性质、微观孔径及粒径分析试验和载荷试验，获取土性参数及模型因子的概率统计特征；提出分析土性参数空间变异性的有限元数值模拟法；建立考虑饱和非饱和渗流及流固耦合作用的非饱和土地基基础定值法数值计算模型；考虑基本变量的互相关性、自相关性及非正态性，优化适用于非饱和土地基基础的随机响应面法，针对不同类型响应面明确其计算精度判断标准及样本点取样策略；提出适用于相关非正态变量的系统可靠度分析法及变量敏感性分析法；分别对非饱和土地基基础的承载力极限状态、正常使用极限状态及整个系统进行可靠度分析与可靠指标对变量的敏感性分析，揭示地基基础在降雨或地下水位变化等环境条件下的破坏机理，明确可靠度影响因素及影响规律，为基础工程及其它岩土工程的稳定性评价及设计提供指导。

非饱和土地基基础工程存在多种不确定性及相关性，需要采用可靠度方法分析它们对基础工程稳定性及变形的影响。通过对非饱和细粒土进行物理性质、力学性质、水力性质、微观孔径及粒径分析试验和载荷试验，获得了土性参数的概率统计特征。建立了考虑饱和非饱和渗流及流固耦合作用的非饱和土地基基础定值法数值计算模型，编写了相应的数值模拟程序。考虑土体的互相关性及自相关性，采用中心点法及KL级数展开法进行随机场的离散。以科学计算语言Matlab编写可靠度分析的主程序以及随机场离散的子程序，将主程序与随机场离散子程序及数值模拟子程序相结合，提出了考虑土性参数空间变异性的数值模拟法。同时考虑基本变量的互相关性、自相关性及非正态性，与随机场离散的KL展开法相结合，提出考虑土体空间变异性并适用于非饱和土地基基础的KL-FORM法及KL-RSM法。研究适用于相关非正态变量的系统可靠度分析法，推导破坏概率及可靠指标对基本变量分布参数的敏感性分析公式。分别对非饱和土地基基础的承载力极限状态、正常使用极限状态及整个系统进行可靠度分析与可靠指标对变量的敏感性分析，揭示地基基础在降雨或地下水位变化等环境条件下的破坏机理，明确可靠度影响因素及影响规律，为基础工程及其它岩土工程的稳定性评价及设计提供指导。