Experimental and discrete element modeling study on suction stress characteristic curve and soil–water characteristic curve of unsaturated reticulated red clay

To explore the effect of suction stress on effective stress, shear strength, and the relationship with the soil–water characteristic curve of unsaturated reticulated red clay, a series of triaxial compression tests, soil–water retention tests, and particle flow code 3D (PFC3D) simulation under different matric suction and net confining pressure was conducted. The suction stress characteristic curve (SSCC) and soil–water characteristic curve (SWCC) of reticulated red clay was obtained. These test results show that the effective stress based on suction stress converged to the unique failure envelope and that there is an internal relationship between SSCC and SWCC. The simulation results of PFC3D were very close to the laboratory measurements in the observation peak value and variation laws of the stress–strain curve. Based on the discrete element method, PFC3D takes rigid spheres or disks as basic units and simulates practical problems through the motion and interaction of the basic units. The parameters obtained by inversion of the stress–strain curve of PFC3D simulation were basically the same as laboratory measurements. Therefore, PFC3D simulation can be used to obtain SSCC and SWCC. These results are expected to promote the development of unsaturated soil mechanics.