Failure Process And Mechanism Of Drifts' Joint Support System In Jinchuan No.2 Mining Area

Jinchuan nickel mine with enormous mineral deposit and riched rare metals is strategic importance for the national economy, so the central government has paid great attention to its development. However, there are some serious problems in Jinchuan nickel mine, such as broken rock, high geo-stress and shape-distorted ore-bodies, etc., which bring about grave challenges to mineral drift excavation. In the No.2 mining area, by the drifts distributed at different altitudes among hanging-wall rock, the backfilled mining in large hypogeal area without micro-jambs has been carried out at two different altitude mining planes for many years, which results in the appearance of the macro-horizontal jamb between the two mining planes. Recently, with the increasing depth of mineral drift excavation, the drift stability has gradually become an eye-attracted focal problem, especially the more remarkable deformation in excavating the 1178m drift resulted in no enough time for repeated shoring, which greatly affects the progress of mine construction.In the implementation of the project "Effects of Macro-Horizontal Jamb Mining on the Redistribution of Stress Field and the Evaluation of Drift Stability in No.2 Mining Area of Jinchuan Nickel Mine", based on considering the interaction of complicated geohydrologic condition, high geo-stress and special mining method, and using various research methods, especially the finite element simulation, and also including spot investigation, theoretical analysis, we have studied the destroy mechanism of the following-vein direction drifts, and obtain some results as followings:The counteractive effect is the main reason of the 1178m drift breakage. Before the approach of the Macro-horizontal jamb failure, the increasing stress concentration with ceaseless mining in mechanized panels of the macro-horizontal jamb makes the counteractive effect become much stronger, which continually deteriorate the breakage of 1178m drift. After the Macro-horizontal jamb destroyed, the counteractive effect will gradually weaken, consequently, breakage of drift also will weaken. The damage forms of drifts are summarized as follows: The damage starts at the vault, spandrels and bottom which are supported by the reinforced concrete. With the breakdown of these special parts, the stored energy and geo-stress within the reinforced concrete support make the break continue expansion, and finally leads to a whole failure of the reinforced concrete support, so causes the redistribution of the localized stress around drift, as a result, the effective stress on the bolts increase significantly and exceed their bearing stress, which make bolts rapid destroy and total failure. The joint support system of drift completely collapse with the destruction of reinforced concrete and bolts, and then the wall rock with destroyed support will appear dramatic deformation, leading to harmful relaxation and slippage of rocks, which quickly fills up the entire drift effective cross-section. Therefore, it is essential to focus on the study of the different damage times in the various support types, which can provides new ideas for the optimized design of the joint support system. These findings and thoughts should be of great reference value for Jinchuan No.2 mining area by reason of. no similar reports in now literatures.