【作者】 袁俊平；

【导师】 殷宗泽； 包承纲；

【作者基本信息】 河海大学 ， 岩土工程， 2003， 博士

【摘要】 本文所进行的研究架构在膨胀土边坡变形与稳定预报的“双链”思想的基础上，认为降雨入渗过程中膨胀土边坡土体的强度折减主要来源于两个方面：一是降雨入渗时边坡土体中土的性状的变化；二是降雨入渗过程中由于土体含水量的增加变化导致边坡吸力降低。本文着重研究前者，将膨胀土的裂隙性作为反映土体性状的主要方面，通过室内试验、现场观测以及数值模拟分析方法，对裂隙的观测手段与定量化描述、浸水愈合特征、裂隙网络渗流特性、裂隙土体强度特性等方面进行了全面系统的试验研究，在此基础上建立膨胀土边坡裂隙网络入渗的数学模型和非饱和裂隙膨胀土固结的数学模型，并应用数学模型对降雨入渗条件下不同裂隙发育状态时膨胀土边坡中水气运移、强度与变形特征进行了有限元数值分析。 首先，在湖北枣阳试验现场，通过手工素描与拍照的方法对膨胀土裂隙进行了观察统计；在室内，利用远距光学显微镜系统对膨胀土裂隙进行了连续拍照观测，建立了非饱和膨胀土的裂隙概化模型。明确了裂隙度的概念，将其作为定量指标对非饱和膨胀土的裂隙发育发展程度进行描述。并采用蒙特卡洛方法研究了非饱和膨胀土的随机裂隙网络的数学模拟与自动生成。 然后，进行了非饱和膨胀土的单向浸水膨胀试验，研究得出了单向浸水条件下非饱和膨胀土的膨胀变形随时间发展的规律。提出了利用膨胀时程曲线计算裂隙周围土体的膨胀变形量来确定裂隙随浸水愈合过程的方法。还进行了不同部位的膨胀土反复剪试验和不同裂隙发育程度的膨胀土三轴剪切试验，研究了膨胀土强度随裂隙度及土体饱和度变化而变化的规律，并提出了相应的拟合经验关系式。 最后，在试验的基础上，发展了非饱和土的有效应力原理，建立了膨胀土边坡裂隙网络入渗的数学模型和非饱和裂隙膨胀土固结的数学模型，并编制了相应的有限元程序USFEM和UCFEM。所建立的数学模型充分考虑了裂隙的渗透、变形与强度特性，可以模拟裂隙在水分入渗过程中逐渐愈合的过程。利用有限元方法对非饱和膨胀土边坡的降雨入渗过程进行了数值模拟研究，全面研究了膨胀土边坡中水气运移、强度与变形特征等。程序结果定量描述了不同裂隙分布、不同裂隙发育程度对膨胀土边坡降雨入渗过程的影响，定量描述了裂隙在降雨入渗时的愈合过程，以及边坡土体强度、边坡稳定性随降雨入渗变化的过程。通过对现场情况数值模拟结果的分析，揭示了非饱和裂隙膨胀土边坡降雨入渗的特点，并据此，对膨胀土边坡工程的设计和施工提出了建议。更多还原

【Abstract】 "Two Chain" model for deformation and stability prediction of expansive soil slope is the framework for this research, in which it is considered that the reduction of strength of expansive soils during infiltration is mainly resulted on two aspects: 1) soils characteristics variation and 2) suction reduction while water content increasing. Focused on the former in this paper, the fissures of expansive soils regarded as most important characteristics are analyzed through laboratory test, field observation and numerical simulation. Scheduled experimental researches are carried out on quantificational description of fissures, healing of fissures during infiltration, seepage characteristics of fissures network and strength characteristics of fissured soil. Based on tests results, numerical models for fissures network seepage and unsaturated fissured expansive soil consolidation are developed and applied to a finite element method analysis of an expansive soil slope during infiltration under different fissures states.Firstly, the expansive soils fissures at test field in Zaoyang, Hubei province, are observed and counted by sketch and photograph, and expansive samples are by continuous photographic measurement using long-distance-microscope-system in laboratory. Generalized model of fissures distribution for unsaturated expansive soils is put forward. The conception of fissures degree is clarified and used to describe the fissures growth extent in unsaturated expansive soils. Numerical simulation and auto-generation of random fissures network are conducted by Monte Carlo method.Secondly, one-side immersion swelling tests are carried out, and time-travel expansive process regulations are obtained. A method is proposed to calculate expansive deformation of soils round fissures by time-travel expansive curve, and then to determine fissures’ healing progress. Cycled shear tests for different part expansive soils and triaxial shear tests for different fissures growth extent expansive soils are carried out. The strength variation of expansive soils along with the variation of fissures degree and saturation degree is summed up, and fitting formulas are summarized.Finally, based on the test results, effective stress principle for unsaturated soils is developed. Numerical models for fissures network seepage and unsaturated fissured expansive soil consolidation are developed and finite element programs named USFEM and UCFEM are designed respectively. In the numerical models, fissures characteristics of seepage, deformation and strength are overall considered, and then fissures healing process can be simulated. The numerical models are applied to the analysis of water-air transmission, deformation and strength variation in an expansive soils slope during infiltration. The results of numerical simulation quantificational describe the influence of fissures position, fissures growth extent on expansive soils slope infiltration process, fissures healing process during infiltration as well as the variation process of soils strength and slope stability. The analyses on numerical simulation results reveal the characteristics of water-air-transmission and deformation in the unsaturated expansive soils slope during infiltration. According to numerical simulations, some suggestions are proposed for design and construction of expansive soils slope.更多还原