湿化效应对高填方红土路基变形影响及控制研究

Based on the view of wetting deformation and intensity change caused by soil soaking wet at the same time, the effect of wetting behavior on high filling laterite subgrade deformation is researched. First,the experiment research of soil wetting behavior is carried out by test, including the laterite wetting deformation triaxial test, unsaturated laterite strength test and rainfall or laterite filling subgrade indoor large-size model test under flooding conditions,the law of influence of laterite dry density, initial moisture content and physical characteristics on soaking deformation and intensity is studied. Wetting deformation characteristics of repeatedly wetting，partial wetting and offload conditions is researched. The quantitative strength expression of unsaturated laterite wetting deformation and strength is given.The second, saturated-unsaturated soil permeability consolidation law is derived from theory under the influence of wetting behavior.Coupled equations based on the saturated-unsaturated soil consolidation theory are established by considering the soil wetting deformation and strength of unsaturated soil with moisture content changes,and applied to geotechnical engineering finite element calculation.The corresponding finite element calculation program is developed.The deformation law of the subgrade under the wetting behavior is analyzed by using developed program. The influence of dry and wet conditions of subgrade ,filling dry density ,filling moisture content, particle size distribution and vehicle load factors on the subgrade settlement is researched.According to the numerical analysis results and the indoor model test results,deformation control measures are provided.

基于土体浸水湿化会同时引起其湿化变形及其强度变化的观点，研究湿化效应对高填方红土路基变形影响。首先从试验上开展土体湿化效应试验研究，包括红土湿化变形三轴试验、非饱和红土强度试验及降雨或浸水工况下红土填方路基室内大尺寸模型试验；研究干密度、初始含水率及级配等物理特性对湿化变形及强度变化影响规律，研究反复湿化、部分湿化及减荷条件下湿化引起的湿化变形特征，建立非饱和红土湿化变形以及非饱和红土强度定量表达式；其次从理论上研究湿化效应影响下饱和-非饱和土体渗透固结规律，建立能考虑土体湿化变形以及非饱和土强度随含水率变化的饱和-非饱和渗透固结耦合方程，研究其在岩土工程有限元计算中应用方法，完成相应有限元计算编程；利用开发程序分析湿化效应作用下路基的变形规律以及路基干湿状况、填筑干密度、填筑含水率、颗粒级配及车辆荷载等因素对路基沉降变形影响；根据数值分析成果与室内模型试验结果，提出相应变形控制措施。

红土在江西广泛分布，被大量用作路堤填料，红土浸水湿化对路基变形影响不可忽视。项目通过GDS非饱和土三轴仪、全自动控制三轴仪及压力板仪等开展了红土湿化变形的三轴试验，研究了不同填筑干密度、粘土矿物含量、湿化应力路径、部分湿化等条件下湿化变形特性，以及非饱和红土土-水特性及强度变化规律，取得了一系列研究成果；通过试验获得了部分湿化变形与应力状态及饱和度的关系式，建立了非饱和土扩展非线性弹性本构方程；同时从热力学理论及液桥计算模型角度，提出了不等径土颗粒组合微观模型下的土-水特征曲线理论解，并结合突变理论从理论上建立了反映湿化效应的湿化变形本构关系，即建立了含水率、基质吸力、湿化变形这三者之间的关系式；编制了可考虑部分湿化变形、强度随含水率变化的饱和—非饱和渗流及应力变形有限元程序。数值模拟了路基浸水下湿化效应对路基沉降变形的影响规律，并与室内路基模型试验结果进行对比；分析了填筑干密度、浸水高度、粘土矿物含量、路堤高度等对路基沉降变形规律。结果表明填筑压实度（干密度）对湿化变形影响较大；红土性质对湿化变形影响也大，压实度相同情况下液限相对较高红土湿化变形大；相同浸水高度下路堤越高产生的湿化变形越大；浸水高度越高产生的湿化变形也越大；结论对红土地区路基设计及施工具有重要的指导意义。