HYDRO-MECHANICAL BEHAVIOUR OF NANJING XIASHU LOESS IN DESORPTION MOISTURE STATE

A series of water-retention tests are carried out with different net confining pressures by the modified GDS unsaturated soil testing equipment. The deformation behaviour and water-retention characteristic of Xiashu loess are analyzed. Based on the data fitting for the soil-water retention curve of Xiashu loess with the van genuchten model, the influence of net confining pressure on the suction-stress characteristic curve(SSCC) of Xiashu loess is presented. The hydro-mechanical behaviour of Nanjing Xiashu loess in desorption moisture state is systematically studied. The experimental results show that net confining pressure and matric suction have significant influence on the deformation behaviour of Xiashu loess. When the matric suction of Xiashu loess becomes higher, the compressibility tends to be lower. The binary exponential function model is put forward to forecast the exterior relations between void ratio and stress state variables. The distinctness of water-retention characteristics of Xiashu loess follows net confining pressure rise. The power function between air-entry value and net confining pressure is reached. Net confining pressure influences the water-retention characteristic of higer compressive soil more significantly. With the increase of net confining pressure, the void ratio of Xiashu loess proceeds a convergence, and the influence of net confining pressure on the water-retention characteristic has started to decline in due process. The external load on Xiashu loess affects the SSCCs piecewise. In the boundary-effect zone, with the increase of net confining pressure, the difference between SSCCs decreases gradually. In the transition zone, the variations of the differential coefficient of suction stress with the state variables is isolated from the external load. Physical meaning and calculation method of suction stress function at high suctions acquired from theory of electrical double layer are approached. The effective boundary saturation degree is proposed as the demarcation point of suction stress function.