Mine Strata Pressure Law of Fully Mechanized Top Coal Caving Mining Face in Shallow Depth and Determination of Working Resistance for Powered Support

According to the serious mine strata pressure behaviors of the fully mechanized top coal caving mining face in a shallow depth and the frequently opened problems of the safety valve,an analysis study was conducted on the working status of the hydraulic powered supports applied in No.39107 fully mechanized top coal caving mining face in a shallow depth of Pingshuo No.3 Underground Mine.A mine strata pressure monitoring and measuring system was applied to the site measurement of the working resistances of the powered supports.The initial roof weighting step distance of the coal mining face measured was 33.7 m,the average periodical roof weighting step distance was 20.7 m,the average circulation resistance of the powered support was 9 700 kN during the periodical roof weighting period,the average open rate of the safety valve was 3.7% and the initial support force of the hydraulic powered support applied to the coal mining face was low in general.The analysis showed that there were three irrational working statuses existed in the hydraulic powered supports.The set pressure of the safety valve was irrational,the loadings of the front and real legs were not balance and the cross sprinklings were occurred in some powered supports.In combination with the site measured data,theoretical calculation was made and the rational working resistance obtained of the powered supports applied in No.39107 coal mining face should not be lower than 12 000 kN.