不同干燥温度条件下非饱和红黏土裂隙演化及抗剪强度变化规律研究

CHANGE RULES OF CRACKS AND SHEAR STRENGTH IN UNSATURATED RED CLAY UNDER DIFFERENT DRYING TEMPERATURES

温度作为重要外界因素,对红黏土的强度特性和裂隙性具有重要影响。为研究干燥温度、含水率和干密度对非饱和红黏土强度特性和裂隙发育的影响,对不同蒸发温度条件下不同初始状态的非饱和红黏土进行直剪试验和干燥试验。分析了不同温度下红黏土的强度特性,结合图像处理技术对裂隙的发育规律进行了阐述,并对抗剪强度指标(黏聚力、内摩擦角)和裂隙形态参数(裂隙率)的关系进行了探讨。试验结果表明:裂隙几何参数(裂隙总长度、节点数和裂隙率)随着温度升高而增大。干密度越低,含水率越大,裂隙指标随温度的变化幅度越大,裂隙也越发育。张拉应力的存在是裂隙产生的主要力学原因。黏聚力随温度升高先增大后减小,衰减的幅度和干密度有关。随着温度升高,内摩擦角先缓慢增长,而后增速加快,含水率越低,变化越明显。随着裂隙率的增加,黏聚力先增多后减小,内摩擦角则不断增长。

As an important external factor,temperature has an important influence on the strength and fracture properties of red clay.Direct shear test and desiccation tests were conducted under different drying temperatures on unsaturated red clay with different initial state to investigate the effects of drying temperature,dry density and water content on strength and cracking characteristics.The evolutionary rules of the strength and fracture under different temperatures are analyzed.The relationship between shear strength index(cohesion and internal friction angle)and fracture geometry parameter(joint rate)are discussed in this paper.The results show that total joint length,nodes and joint rate increase with the increase of temperature.The amplitudes have significant increases when the water content is the maximum moisture content and the dry density is the minimum dry density.Tensile stress field in soils is the main mechanical cause of cracking.Cohesion increases firstly and then decreases with increasing temperature and the attenuation amplitude is related to dry density.Internal friction angle becomes lower firstly and then higher when the temperature is rising.The lower the water content,the more obvious the increase.As the joint rate increases,the cohesion becomes larger firstly,and then smaller,and then internal friction angle continuously increases.