Engineering geology, ground surface movement and fissures induced by underground mining in the Jinchuan Nickel Mine

The Jinchuan Nickel Mine is the largest underground mine with cut-and-fill mining in China. In 1999, there appeared evident ground surface movement and many ground fissures in Jinchuan No. 2 Mine. Following an introduction to the engineering geology and mechanical properties of the rock mass in the Jinchuan mine areas, this paper reveals the features of the measured in situ stresses and puts emphasis on an analysis of the mechanism of surface movement and ground fissures induced by the underground mining with backfill. It is indicated that both the fault structures and the alteration contact zones are well developed as the dominant engineering geological characteristics in the Jinchuan mine areas. The stress redistribution in surrounding rocks resulting from the mining, the low stiffness of the filling body, the existence of the void space and the influence of on-going mining activities is the main reason for the occurrence of surface movement and ground fissures.