Rock mass characterization to determine the appropriate support systems for Kansanshi decline(Solwezi, Zambia)

Abstract

The objective of this research was to characterise the rockmass to determine appropriate support system for the decline with the 4.5m height and 4m wide in highly aquifer strata, recharging the water flow of 18, 000 cubic meters per day. As a result production targets reduced due to excessive water coming from subsurface strata or water bearing structures. This study reviewed the most used universally classification methods in the mining and tunneling systems for support design purpose, such as the Rockmass rating (RMR) and Q-System. The design methodologies that were used in this research involved site visits, geotechnical mapping to determine structural orientation on the portal position, core logging and software application to determine effective support system.The data obtained in the mapping exercise was subsequently used to analyze the differences in rock mass conditions in areas of different formation. The rockmass was divided into domains of similar characteristics and into the expected formations of similar rock properties. The study established that, the support systems should be both passive and active (hybrid support). Besides in this research it is established that, the use of mesh wires and shortcreting constitutes the major portion of passive support. While cable bolts, rock bolts constitutes active support.The study concluded that, the method of applying rockmass characterisation using either the Q-system or rockmass rating proved to be a quick, easy and effective methodology to determine appropriate ground support design for any ground conditions. Recommendations provided to design support system were based on the results obtained from rock mass characterisation using the Q-system and rockmass rating.