Abstract: It is of great significance to understand the influence of matric suction on shear strength behavior of ion-absorbed rare earth unsaturated ore body. Hence, the weakening of the strength of the ore body caused by water can be recognized. The soil-water characteristic curve and shear strength of the ore body were measured in the field. The influence of matric suction on the shear strength of the ore body was obtained. As the matric suction increased, the inner friction angle of the ore body increased slightly, and the cohesive force increased greatly. According to the analysis of the physical meaning represented by the air entry value, we could see that when the matric suction was lower than the air entry value, the contribution rate of matric suction to shear strength could be regarded as a constant. When the matric suction was higher than the air entry value, the contribution rate of matric suction to shear strength decreased gradually. The improved model of unsaturated strength was proposed by taking the air entry value as the boundary point. The absolute error between the calculated value obtained by this model and the measured value was within 15%, and better than the other models prediction results

Key words: 1. School of Resources and Environmental Engineering, Jiangxi University of Science and Technology, Ganzhou, Jiangxi 341000, China, 2. School of Architectural and Surveying & Mapping Engineering, Jiangxi University of Science and Technology, Ganzhou, Jiangxi 341000, China