Dynamic Failure Research On Vertical Gob Group Under Scale Remnant Ore Recovering

With the continuous development of mining technology, low-grade ore, left around gobs in the former mining stage, has now been redefined as minable resourses. Mining engineerings were arranged to recycling the remnant ore resourses. Gobs existed in ore body, weakened the mechanical properties of rock mass and seriously restricted the safety during remnant ore mining. The coupling effect among adjacent gobs made the safety of residual ore mining more complicated.Taking KT5 ore body of a domestic gold mine as research object, the paper made a comprehensive failure research on vertical gob group under remnant ore mining on scale by field investigating, data collecting, theories analyzing, numerical simulating, and engineering validating etc.. The main wrok of this paper are as follows:(1) Analyzing factors affecting the stability of vertical gob group systematacially. Obtaining the distribution situation of remnant ore resourses and gobs existed in all levels of KT5 ore body after detailedly investigating the field and collecting data.(2) Simplifing equivalently rock mass inside vertical gob group as flat poles, converting gob group into flat poles system, building rigid frame structure failure model of vertical gob group. Based on the failure model, a new instability analysis method which was used to evaluate the statistic stability of vertical gob group was presented. With the method, the statistic instability situation of vertical gob group existed between line 63 to 67 of KT5 ore body was researched before and after mining the pillar remnant rock mass of the highest level.(3) Discretizing the mass of vertical gob group rigid frame model, converting gob group into multi-freedom degrees structure system, building a time-history response model of vertical gob group. Based on the response model, a new rock mass time-history response analysis method was presented. The analysis results, together with rock mass vibration velocity criterion, were used to evaluate dynamic instability situation of vertical gob group. With the method, the dynamic instability of vertical gob group existed between line 55 to 57 of KT5 ore body were researched while mining the roof rock mass.(4) Taking single-row vertical gob group existed between line 67 to 69 and double-row vertical gob group existed between line 59 to 63 of KT5 ore body as research objects. Using rigid structure model failure analysis method, statistic stability situation of both single-row and double-row vertical gob groups were studied before and after mining the remnant roof rock mass on scale, together with time-history response analysis method based on structure modal, dynamic stability situation of both single-row and double-row vertical gob groups were researched while mining the remnant roof rock mass on scale. Comprehensively considering the instability situation of both single-row and double-row vertical gob group, theoretical support and feasible solutions were put forward for remnant multi-roof rock mass mining engineering of both single-row and double-row vertical gob groups.