In Japan, a bench cut method is mainly applied for limestone quarries. As most of the mines are located in the mountain regions and steep slope mountains, the shaft and the underground opening for installation of facilities such as crushing equipment are applied in order to provide workability and economic efficiency for transportation and crushing ores. However, as the mining operation proceeds, the level of the pit will be down and the distance between the mining area which is the bottom of the pit and the opening for underground facilities such as crushing equipment become to be short. In order to maintain the safe mining operation and the stability of the underground opening, the appropriate distance between them has to be maintained. Therefore, in order to develop the guidelines for safety distance between the mining area and the underground opening for installation of facilities such as crushing equipment under different rock mass conditions in a limestone quarry, a series of numerical simulations are conducted by means of finite differential code “FLAC3D”.