In order to investigate the influence of end effect on the waste-soil sample strength under uniaxial compression, the influence law of end effect on the uniaxial compression strength is numerically simulated by the FLAC3D software, and the reliability of the numerical model is verified by comparing it with the test results. Based on the above model, the influence of end effect on the lateral displacement and stress state of waste-soil samples is simulated, and the formation mechanism of end effect under uniaxial compression is revealed. The results show that, when the friction coefficient increases from 0 to 0.4, the uniaxial compression strength and percentage of triaxial compression units first increase rapidly and then slowly and then finally remain invariant. With the increase of the friction coefficient, the lateral displacement of the sample is significantly reduced. On the end surface, the nearer to the edge one is, the greater the decrease is. The triaxial compression region on the axis section is triangular in distribution; with the increase of the friction coefficient, this region increases first rapidly and then slowly and then finally remains invariant. The end effect produces lateral compression stress by reducing the lateral displacement of the end surface of samples, and lateral compression stress causes the sample to enter the triaxial compression state. With the increase of the friction coefficient, the triaxial compression region increases gradually, and thus, the uniaxial compression strength of the entire sample increases.

Water storage capacity has always been the core component of the underground water reservoir in open-pit coalmines. Taking the western underground water reservoir of Baorixile open-pit coalmine as the research background, boreholes in the waste dump overlying the underground water reservoir were designed and drilled, and the capacity characteristics of the underground water reservoir were studied by a layered summation method. These test results revealed that: (1) the regional strata from shallow to deep are the near-surface loose layer, upper bench loess, mixed stripping material, glutenite water reservoir layer and rubble collecting ditch; and the glutenite water reservoir layer is the main water storage body of the underground water reservoir. (2) Permeability coefficient, porosity, layered and cumulative water storage of the western underground water reservoir in Baorixile open-pit coalmine increase with the elevation increase, and show a quadratic function relationship. (3) The total storage capacity of the underground water reservoir is 1.2234 Mm3, and the average porosity is 0.1003, that is, each volume of the water storage medium can store 0.1003 volume of water. These results provide a scientific basis for the evaluation and determination of the water storage capacity of the underground water reservoir in open-pit coalmines.