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

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.