Mutambo V. Controlling stress condition of rocks and their parameters with vertical crater retreat method for example at Luansha division (Zambia)

Defending results of theoretical and experimental researches in designing and introducing new technology of breaking mineral deposits using vertical crater retreat method based on conditions at Luansha. Designed technology of breaking stressed rocks is aimed at using energy of mine pressure in explosive blasting. Methods of controlling energy of mine pressure with the aim of using it in blasting stressed rocks have been considered. In the dissertation work, conformity distribution of static stresses in exposed rock mass and their influence on effectiveness of breaking stressed rocks in blasting using different methods of ore - breaking, have been established. In the dissertation, ability of raising effectiveness of blasting works using static and dynamic stresses on a massif has been shown depending on different sizes of compensating space and depth of mining. Theoretical and experimental researches have established condition of rock mass and parametrical zones of influence of static stresses with di fferent signs. Moreover, dependence of tensile zone on sizes of compensating space, their orientation, thickness of ore-body, depth of mining and method of ore-breaking, has been established. Possibility of improving effectiveness of blasting works in breaking stressed rocks have been shown with spherical charges on an arched type of compensat-ing space using vertical crater retreat method. Methods of calculating parameters of ore-breaking have been precisely for-mulated in regard to stress condition of rock mass with vertical crater retreat, and also technical economical indexes. Analysis of mining methods used at Luansha mining enterprise has been done. Its noted that in order to improve production there is need to introduce modern technology of breaking minerals. Based on research and on analysis of current statistics concerning the above method (VCR), its clear that current traditional method of VCR does not allow essentially to improve quality of rock fragmentation and technical economical indexes. In s tope extraction when breaking rocks using this method, stress con-dition of rocks and its influence on the effect of explosion is not considered. Therefore, based on the results of research, a new technology of breaking stressed rocks using vertical crater retreat method has been worked out. In com-parison with traditional VCR method, the new technology will greatly improve rock fragmentation and raise technical economic indexes at mining interprises. Analysis of given dependences, showed that inter-relating parameters of breaking rocks with depth of mining and sizes of compensating space makes it possible to increase effectiveness of breaking. Based on carried research, method of determining parameters of locating spherical charges allowing to inter-relate energetical characteristics of explosive materials with physical properties of rocks and their stress condition using VCR has been worked out. More over, in dissertation work, effective mining system has been designed allowing dramatically to reduce specif ic extent of mine workings and raise tech-nical economical indexes in general. In the last part of dissertation, technical and economical valuation of de-signed technology has been carried out supporting its effectiveness. Results of research can be used not only at Luansha mining enterprise (divi-sion) but also at other mining enterprises having similar geological and technical mining conditions. Key words: stress condition; vertical crater; breaking; spherical charge.