Study On The Slope Stability Under Condition Of Underground Mining Combined With Open Mining In Tongshankou Mine

In the condition of underground mining combined with open-pit mining, mining effect will be superposed. Mining slope will receive several induced stress fields and deformation law of slope rock mass will be more complicated. With more and more mines transforming into underground mining and due to lack of awareness on new movement law, accidents of open pit slope collapse and surface subsidence, landslides and other disasters dump caused by underground mining occurred frequently, leading to an increase costs of open slope and dump maintenance, which not only brings huge economic losses, but also make the direct impact on mine safety production. Therefore, the research on slope stability under the combinational action of two mining approaches is necessary. This paper, taking Tongshankou Mine as engineering background, adopts methods and means of theoretical analysis, field geological survey and indoor numerical calculation to explore effect rules on pit slope under excavation condition of different ore bodies dip and then make research on key slope. The main research results are:(1) Slope mass will emerge two typical sliding phenomenon with joint effects:the one is rock mass sliding along the slope, and the other dropping to the deep mining gob.(2) Underground excavation conditions, the small dip ore bodies make more greatly impact on open-pit slope than large dip ones and with the angles growing the influence degree changes little.(3) Slope at NO.9 prospecting line profile map in Tongshankou Mine is in stable state after excavation but hanging wall steep slope may occur partial damage and footwall slope is likely sliding overall; the safety factor of hanging wall slope is 2.3 and footwall slope 4.3.(4) Based on project status and the possible failure modes, the measurements like filling back of foot slope and cut some top of slope to reduce load are adopted to make slope stable. It is suggested to implement displacement monitoring to key slopes after the mine transferring into underground mining.