The Influence of Geotechnical, Geological and Mining Factors on the Formation of Sinkholes at Lubambe Mine, Zambia

Abstract

Mining-induced sinkholes are a common feature in underground mines. Sinkholes usually disrupt mining operations and associated infrastructure when they occur. This paper presents a case study of the Lubambe copper mine, where nine (9) sinkholes have been reported on the eastern and southern limbs. The development of sinkholes has resulted in increased mining costs due to the closure of the 182 mL decline on the eastern limb and the 175 mL truck route on the southern limb. This study establishes the influence that poor ground formation, rock stability, geological structures, and inappropriate mining practices have on the formation of surface sinkholes. Assessment of ground condition was done by core logging, and borehole analysis was conducted using GEM4D-BasRock software to classify the rock mass quality based on RQD, RMR, Q-System and GIS. Assessment of the mining operational environment was focused on the effects of varying stope designs and sequencing on ground stability. Results of the study indicate that the formation of surface-induced sinkholes is attributed to historical mining in weak rock formation and weathered rock coupled with subsequent failure of unsupported stopes with stope height between 8 and 25 metres and less stand-up time of 7 days.