CASE STUDY AND MECHANISM OF WATER INVASION HAZARD IN NANJING GYPSUM MINE AT DEEP DEPTH

The especia lly big w ater invasion event occurred on September 11, 2006 in N anjing gypsum m ine. It changed the g roundw ater flow field of them in ing area and surround ing influenced area, and resulted in ground set t lement and ground fissures over the m in ing space and periphery zone, and led to surface structure destroyed such as road, houses, and w orkshops, and caused tremendous econom ic losing inc lud ing m ine c losed up. The N anjing gypsum m ine is a typical underground deep m ine w ith geo log ica l eng ineering issues. The main factors influencing the underg round m ining stab ility, m ine hazard, and geo- env ironm ental problems are rock mass properties and the ir structures, wh ich are especia lly as faults, jo ints or fissures etc. , the ir sa le, mechanics and spatia,l and wa ter abundance and conductiv ity. The intensive karst w ater abundance zones ex ist in the rock layer above the ore bed and in its south, wh ich are the d irect w ater invasion source. The soft rock ( ore ) properties, together w ith deep m ining, m ining d isturbance to the orig ina l stress fie ld surround ing the m in ing space, the de format ion activa tion o f the ex isting fau lts or jo ints or fissures, provides thew ater invasion hazard conditions.