控制厚度条件下土体干缩开裂的界面摩擦效应

土体厚度和界面粗糙度对土体干缩开裂有着重要影响,为了探究土体在不同厚度和界面粗糙度条件下的干缩开裂特性,开展了一系列室内干燥试验。试验中共配置了9组初始饱和的泥浆样,分别设置3种不同的土体厚度和3种不同的界面粗糙度,并在恒温30℃的条件下进行干燥,实时记录试样含水率变化及表面裂隙的演化过程,利用数字图像处理技术,对裂隙网络进行了定量分析,得到不同厚度和不同界面粗糙度条件下土体龟裂的动态发展过程及相关参数。试验结果表明:①界面粗糙度越大,龟裂发育速度越快,然而土体厚度越大,龟裂发育速度越慢,且土体整体收缩效应越明显;②界面粗糙度越大,龟裂发育程度越高,然而增加土体厚度可以削弱界面粗糙度对龟裂发育过程的影响;③土体厚度和界面粗糙度都对土体开裂时的临界含水率有重要影响,且两者对龟裂发育过程的影响具有耦合作用关系。最后,结合土体干燥收缩特性,探讨了上述两种因素对龟裂的影响机理。

Effects of boundary friction and layer thickness on desiccation cracking behaviors of soils

As the layer thickness and interfacial roughness of soils are the most important factors affecting their desiccation cracking, a series of desiccation tests are therefore conducted to investigate the shrinkage and cracking characteristics under various soil thicknesses and interfacial roughnesses. In the tests, nine slurry specimens of initial saturation are prepared and dried under a constant temperature of 30℃ and three different soil layer thicknesses and interfacial roughnesses. The change of water content and surface cracking are kept in a real-time record during the whole process of drying. The image processing technique is employed for quantitative analysis of crack network. The dynamic desiccation cracking process is recorded and the relative parameters are obtained under different soil layer thicknesses and interfacial roughnesses. The results show that: (1) The larger the interfacial roughness, the faster the rate of cracking development, while the greater the thickness of soil layer, the slower the rate of cracking development, and the more significant the effects of integrated shrinkage of soils; (2) The larger the interfacial roughness, the higher the degree of cracking development. However, the increase of soil thickness can restrain the influences of interfacial roughness on cracking development; (3) The influences of interfacial roughness and soil layer thickness on cracking have certain influences on the average water content during the initial cracking of soils. Additionally, the influences of the two factors on cracking development have coupling relationship. Finally, the influence mechanism of the two factors is explored by expatiating the mechanism of soil shrinkage.