Study on Suitability of Hydraulic Powered Two Lag Shield Caving Support in Pingshuo Mining Area

Due to the ZFY12000/23/40D two leg hydraulic powered shield caving support first applied to Pingshuo Mining Area, in order to evaluate the suitability of the powered support to the mining area, the powered support structure, bearing loads, hydraulic balance jack, electric and hydraulic control system and actual applicati on conditions were generally studied.The study results showed that powered support structure could meet the top coal caving requirements.The site measured periodic al strata pressurized step distance would be 11.6 m and the dynamic load coefficient would be 1.71.The working resistance of the powered support was 5 941 kN and th e max working resistance would be 12 443 kN.The loading differential of the two legs would be 5.96% .After the top coal caved, the load on the powered support would b e reduced by 13% .After the top coal caved, the max load variation value on the hydraulic balance jack would be 30.23% The site measured time of the powered support forward advancing was 29.8 s in the initial period, was 59.7 s in the later period and the top coal caving time was 54.3 s.The occasions to pass through the faults and th e weathered oxidized zone, the roof failing in the front of the powered support and the coal wall spalling for the coal mining face were increased.There were many failur es occurred in the controller of the electric and hydraulic control system. The paper held that the ZFY 12000/23/40D two leg hydraulic powered caving support could hav e a good suitability under the such geological conditions.