Influence of irrigation on slope stability of dump in arid desert area of Northwest China: a case study of Xinxing coal mine, Wuhai

The seepage mechanics theory was combined with the geomechanics theory to reveal the fluid-solid coupling mechanical mechanism of slopes on the coal mine dump under irrigation in an arid desert region of Northwest China. The Darcy law and the mass conservation law both were introduced to derive the fluid-solid coupling analysis method. Taking Xinxing coal mine of Wuhai city as a sample, the finite element software ABAQUS was used to establish the slope stability model of unsaturated soil under the fluid-solid coupling theory. Twelve types of irrigation schemes were used in the numerical simulation by choosing four types of equivalent irrigation intensity (i.e. 5 mm/h, 20 mm/h, 45 mm/h and 70 mm/h) and three sorts of continuous irrigation time (i.e. 2 h, 9 h and 15 h) according to the water requirement of vegetation and the rainfall intensity, respectively. The numerical results were compared with the existing experimental results. Results showed that the four indicators, including vertical deformation of slope, pore water pressure distribution, equivalent plastic strain, and safety factor, developed in the direction which was not conducive to the slope stability when the infiltration water increased. When the equivalent irrigation intensity was 70 mm/h and the irrigation time was 15 h, the vertical deformation of the slope increased significantly and the safety factor decreased rapidly to 1.03. Under the condition of meeting the water requirement of vegetation growth, the irrigation intensity should be controlled, and short duration and interval irrigation should be adopted to reduce the possibility of slope runoff. Simultaneously, the measures of interception and drainage as well as slope protection should be taken. © 2019, Zhejiang University Press. All right reserved.