Scree formation on nonmining flank of an opencast and its impact on vegetation restoration

The purpose of the conducted research is to study the regularities of scree formation and assess their impact on self-vegetation of disturbed lands after mining of building stone deposits. The processes of natural formation of scree have been studied, their layering and gravitational alignment have been determined, the factors causing pit bench collapse have been identified. Simulation of the scree formation process allowed to establish the dependence of rock spreading distance on bench height, bench slope angles, as well as on the weight of individual pieces. The slope bench angles with the largest and smallest rock spread distance were found. The simulation showed the influence of the slope bench angles and parameters of the scree formed at the foot of pit benches on the range of debris spread. Three distinct formation stages of scree at the foot of the benches are identified. The angles of transition from one stage of scree formation to another are determined. Recommendations are given to improve the conditions of self-vegetation and minimize the negative factor of scree formation. To form a layer of loose sediments on horizontal bench sites it is proposed to use rocks from scree, which can dramatically reduce the cost of reclamation rather than imported man-made mixture or potentially fertile soils. In order to increase self-vegetation intensity on the flanks of opencasts, it is recommended to increase the bench height and berm width without changing the design angle of the opencast flank slope. To reduce the adverse impact of scree formation on vegetation restoration on the sides at the bench foot, it is proposed to form a trench collecting falling rocks or a rockprotecting wall.