Similar simulation experimental investigation on the deformation and failure character of the stope pillar of gently inclined and medium thick phosphate rock under pillar and room caving

Based on the gently inclined medium thick phosphate rock of the deep part of the east mining section of +2150 level of Jinning-Six mine of Yunnan phosphate Co., Ltd, the similar material physical model simulation experiment of the stability of stope pillars under room and pillar mining was carried out by the mine pressure plane stress modeling experimental frame of college of resource and environmental sciences. Based on the experimental results, the deformation and failure changing law of the above roof, surrounding rock mass and stope pillar during the mining along the strike direction of phosphate were investigated. The experimental results showed: (1) With the increasing of the scope of mined-out area, the fwassure zone and separation layer zone of the roof in the original mined-out area of the stope were pressed compact step by step. And when the space range of the mined-out area reached some scale, the deformation of the fwassure zone and separation layer zone of the roof in the original mined-out drived to stabilwasation, and the sustain action of it to the gravity fore of the overlying strata was reexternalization. (2) After the mining, the subsidence region of the overlying strata of the stope mainly concentrated the roof and surrounding rock mass which beside the mined-out area, the position of the maximum subsidence point was in the center zone of the excavation space, with the increasing of the dwastance from the center of the stope along the trend and normal of the ore body, the subsidence value of the overlying strata of the stope was monotone decreasing. With the increasing of the region of the excavation space, the mining influence region and the mining influence degree of the overlaying strata of the stope gradually increased. And the corresponding position of the maximum subsidence zone dynamically forward leaded, the final subsidence curve of the overlying strata was a bowl shaped curve. (3)The deformation and failure characteristics of the overly- - ing strata of the stope roof was obviously divided into three stages under the room and pillar caving, the overlying strata of stope could be divided into caving zone, fractured transfixion zone and micro-fractured loose zone. When the excavation the ore body of the rooms was completely finished, it recovered the individual stope pillars in the experiment, and the remain stope pillars suddenly appeared integrity-large-scale sloughing control and unstable failure, which presenting obviouse "domino effect". The related research results could provide theoretical guidance and suggestions concerning the underground mining for the phosphate rock of the deep part of the east mining section of of Jinning-Six mine of Yunnan phosphate Co., Ltd and similar condition mine.