【作者】 陈善雄；

【导师】 赵文光；

【作者基本信息】 华中科技大学 ， 结构工程， 2006， 博士

【摘要】 膨胀土工程问题是我国高速公路建设中遇到的一大技术难题,结合实际工程,研究膨胀土的工程特性与处治技术具有重要的理论意义和工程应用价值。结合实际工程,采用室内试验、现场试验、原位监测和理论分析与数值模拟相结合的手段,对膨胀土工程性质进行综合研究,进而探讨膨胀土的分析方法与处治对策,为膨胀土地区工程建设提供科学依据,同时,推动膨胀土及非饱和土力学学科的发展。本文的主要研究内容和成果如下:1、开展了高速公路膨胀土病害调研,揭示了公路膨胀土病害的特征与原因,加深了对膨胀土危害的认识,可为膨胀土处置方案的制定提供指导。2、对反映和表征膨胀土胀缩机理和特性的指标进行了深入探讨,以能充分反映和表征膨胀土胀缩机理和特性的液限、塑性指数、自由膨胀率、<0.005 mm颗粒含量、胀缩总率等5个指标作为膨胀土的判别指标,建立了一种新的膨胀土判别与分类方法-膨胀土判别与分类的模糊综合评判法,并通过试验进行了验证。该方法的采用将使评判结果尽量客观,从而取得更好的实际效果。3、系统地开展了膨胀土工程特性试验研究,全面阐述了膨胀土的压实特性、胀缩特性和强度与变形特性的变化规律及其影响因素,深化了对膨胀土工程特性的认识。4、针对膨胀土边坡入渗的特点,建立了一种新的可考虑裂隙的膨胀土入渗分析的简化等效模型,获得了一种分析土体裂隙入渗的有效途径。简化等效模型根据边坡土体风化程度随深度的变化将土坡分为二层,Ⅰ层为强风化层,该层土的水分运动参数的选取应考虑裂隙的存在而引起的土的渗透性的增加;Ⅱ层为未风化层,可视为原状土的性质,水分运动参数采用原状土的相应参数。开展了膨胀土边坡降雨入渗的数值模拟研究,数值模拟表明:降雨条件下膨胀土边坡的水分运动主要发生在强风化层内。5、针对膨胀土边坡变形和破坏的特点,建议了一种膨胀土边坡稳定性分析的分层处理方法,其具体方法是将边坡分为风化层和未风化层,风化层厚度按大气影响深度确定,其强度参数选用残余强度值,然后用极限平衡方法进行边坡稳定性分析。开展了膨胀土边坡稳定性的数值模拟分析,数值模拟表明:膨胀土边坡稳定性主要受浅层模式控制。6、采用极限平衡分析方法建立了一套能考虑水分入渗的非饱和土边坡的稳定性分析方法,该方法考虑降雨后土坡水分为一分布场,抗剪强度参数为饱和度的函数。提出了一个降雨条件下土质边坡稳定性预测预报模型,其具体思路是:首先用数值方法计算渗流场,然后利用非饱和土的强度理论推求出整个场的强度分布,再利用极限平衡分析方法或有限元方法进行边坡稳定性分析,寻求斜坡稳定安全因数与降雨特征参数的相关关系,如此即可依据气象预报进行土坡稳定性预报。该方法的提出为气候条件下膨胀土边坡稳定性预测预报提供了一种新的思路,为膨胀土边坡的有效处治提供了科学依据。7、成功进行了人工模拟“久旱暴雨”诱发膨胀土滑坡试验,再现了膨胀土边坡失稳中最常见的浅层滑动现象,揭示了降雨引发膨胀土滑坡的内在规律。8、在上述试验研究、理论分析和数值模拟的基础上,开展了膨胀土处治技术研究。建议了膨胀土路堤的结构型式,给出了膨胀土的填筑控制标准,并建议了骨架防护与植物防护相结合的坡面综合防护方案。有关研究成果在襄荆高速公路、合六叶高速公路、周六高速公路、新汉口机场和2319-Ⅱ工程得到了成功应用,取得了良好的技术经济效果,具有良好的推广应用前景。更多还原

【Abstract】 The engineering problem of expansive soils is a technical bottleneck in highway construction in our country, therefore combining the real engineering, studying the characteristics and treatment technology of expansive soils has important academic meanings and engineering values.The engineering properties of expansive soils have been studied synthetically by combining laboratory testing, field testing, in situ monitoring, theory analysis and numerical modeling, and then the corresponding analysis methods and engineering countermeasures for expansive soils have been put forward. It will provide scientific basis for construction in expansive soil region, at the same time, it will push forward the development of unsaturated soil mechanics and expansive soil mechanics further.The main work in the thesis is as following:1. The main damages caused by expansive soils during the construction of highway have investigated, and the disease characters and reason of highway in expansive soil zone have been revealed. It will deepen understanding to harm of expansive soils, and it will provide direction for treatment of expansive soils.2. The indices that can reflect and characterize swell-shrink mechanism and property were analyzed. The analysis indicates that 5 indices such as liquid limit, plastic limit, clay particles, free swell ratio, swell-shrink total ratio can reflect and characterize swell-shrink mechanism and property, hereby these 5 indices have been suggested as identification and classification indices of expansive soils, and a new approach, i.e. fuzzy comprehensive evaluation model for identification and classification of expansive soils has been established. The new model has been validated by experimental findings and it has been shown that evaluation results are more objective and valid adopting the new approach to identify expansive soils3. Experiments on the physical and mechanical properties of expansive soil have been investigated systematically, and the variation laws and its influencing factors for compacting properties, swelling-shrinkage behavior, intensity and deformation behavior of compacted expansive soils have been summarized. It is helpful to understand the engineering properties of expansive soils.4. Considered the rainfall infiltration characteristic of expansive soil slopes, a simplified equivalent model considered fissures for calculating rainfall infiltration in expansive soil slopes has been developed, so an effective approach for analyzing infiltration in fissure clays has been obtained. The simplified equivalent model divides the soil slope into two layers according to the weathering extent of the soil mass with depths. LayerⅠis an intensive weathered one where moisture can be fully evaporated or rapidly absorbed and the moisture movement parameters take into account the strengthening in soils permeability caused by fissures. LayerⅡis an unweathered one where the soils are undisturbed basically and the moisture movement parameters of homogeneous soils are applicable. The moisture movements in unsaturated expansive soil slopes suffering precipitation were simulated numerically using simplified equivalent model, and the simulation results have shown that the moisture movement in the expansive soil slope under rainfall permeation mainly takes place in the extensively weathered LayerⅠ.5. Considered the deformation and failure feature of expansive soil slopes, a simplified method for stability analysis of expansive soil slopes has been suggested. The simplified model divides the soil slope into two layers according to the weathering extent of the soil mass with depths. LayerⅠis an intensive weathered one where depth can be determined by the depth of soil layer influenced by climate and shear strength parameters should adopt the residual strength values. LayerⅡis an unweathered one where the soils are undisturbed basically. The stability of expansive soil slopes were simulated numerically, and the simulation results have shown that the expansive soil slope failure usually is characterized by shallow layer failure.6. Based up the limit equilibrium method,a set of methods that take the effect of rainfall permeation into account to analyze the stability of unsaturated soil slopes has been developed. The proposed method has a consideration that the moisture content in a soil slope after permeation exhibits a field distribution and the shear strength of the soil is the function of degree of saturation. A prediction model, based on mechanical analysis, of slope stability due to permeation of rainwater has been proposed. The prediction of slope stability according to weather forecasting can be realized as the following steps: first, the seepage field may be computed by numerical method, second, the strength distribution of slope can be derived from the seepage field by the strength theory of unsaturated soil, third the slope stability is analyzed by limit equilibrium method or finite element method, at last, the relationship between the safety factor of slope stability and rainfall parameters such as intensify and duration of rainfall can be obtained. It will provide a new thought for prediction of slope stability and scientific basis for treatment of expansive soil slopes.7. A large field test of expansive soil landslide induced by artificial rain has been performed. It successfully reappears the common shallow slide phenomena in expansive soil slopes instability, and the inherent law of expansive soil landslide induced by rainfall infiltration has been revealed.8. Based on above testing, theory analysis and numerical modeling, the engineering countermeasures for expansive soils have been investigated. The structural shape of expansive soil embankment and the standard of controlling compaction of expansive soil for constructing embankment are suggested.A combining measure with engineering revetment and vegetation revetment for expansive soil cutting slopes has been suggested. These research achievements of this thesis have been successfully applied in several constructions, such as Xiangjing Expressway, Heluye Expressway, Zhoulu Expressway, New Hankou Airdrome and 2319-Ⅱengineering, and good technical and economic effect have been obtained, and it will enjoy broad applications.更多还原