Caving of banks by blasting involves problems associated with the development of the caving blast in locaiities with complex relief, with the stability of the slope after formation of an ejection crater at the base of the slope, with the dependence of the parameters of the caved rock on the physical properties of the solid mass, the size of the ejection crater, and the height of the slope (i.e., on the scale of the phenomenon), and so forth. Data on the stabilities of slopes are given in [1][2][3][4][5].Using models made of equivalent materials [6] we have studied the caving of steep slopes when ejection-blasted at the base. The slope caves under gravity after formation of the ejection crater and propagation of compression and tension waves through the bank, i.e., the caving process is the final stage in the motion of the ground during the blasting of a steep slope. We therefore assumed that all the stages associated with the blasting phenomena are already completed, and modeled only the caving stage. We assumed that the solid rock is composed of weak soils, or becomes weak, for example, as a result of weakening of the adhesions between its parts and fracture under the influence of a powerful preliminary blast. These fractures cause a compression wave and reflected tension waves producing instantaneous spalling. In our work with models, we paid special attention to the elucidation of the general laws of the caving process, and did not consider the influence of special features such as stratification, inhomogeneity of the rocks, etc. The slope caves under gravity, and therefore in reducing the geometrical dimensions of the slope, to preserve mechanical similarity between the model and prototype we had to reduce the strength of the ground. This was achieved by using a material of low cohesiveness for the model. We did not take account of the tensile strength of the model material, and paid particular attention to the shear strength characteristics, i.e., the disruptive force of gravity in the system was resisted by the forces of cohesion and internal friction in the ground. Thus in the given case, in conformity with the method of modeling with equivalent materials [6], the scale N of the model is related as follows to the mechanical characteristics of the equivalent and prototype materials:where Pro' rm' and pp, r_ are respectively the densities and shear strengths of the model and prototype materials. Thus, the experimental mo~els were approximate. In particular, in the case of strong ledge rock materials, broken up by local blasting near the focus, the caving process w ill not satisfy the above assumptions.We established by experiment the critical conditions of caving in relation to the dimensions of the ejection crater, the strength characteristics of the solid rock, and the angle of inclination and height of the slope We found that for a given type of ground the critical caving conditions do not depend on the height of the slope. We found a relation between the position of the caving surface, along which the gr...
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