Study On Underground Pressure Law During Terminal And Retraced Mining Of No.103 Fully Mechanized Top Coal Caving Mining Face With Large Mining Height In Changchunxing Coal Mine

Coal mining face retracement is a complicated system engineering, especially for the "heavy" coal mining face with large mining height, the choice of coal mining face retracement mode plays a vital role in the whole Mine mining and safety and efficient mining. And the key to ensure the smooth coal mining retracement is to grasp the detailed roof movement law, and as a basis, to forecast the mine pressure law during the retracement. This article takes No. 103 coal mining face with large mining height in Changchunxing Coal Mine as the research object, observes the underground pressure law in the terminal mining period, masters the roof movement law and the strata behavior characteristics in different mining period(normal and stopped caving period), determines the reasonable parking line and stopped line position, constructes roof structure model in retracement area, preliminary studys the roof pressure behavior law during cutting the retrace channel and supports formal retracement.In this article, theoretical analysis method is used to predict roof movement characteristics, and field measurement is used to determine roof structure characteristics and movement law. The research results show that: in the terminal period of normal caving, the main roof periodic weighting step distance is 26.4m, the relative stability process of the roof pressure is 1.05MPa, the significant movement process of roof pressure is 1.23MPa. In the terminal period of stopped caving, the support bears the static load, the maximum load is 1.12MPa, the minimum load is 0.88MPa. The original designed parking line away from the designed stopped line is about 30m, taking a completely parking way, resulting in a large number of coal losses. Redesigns the reasonable parking line and parking technology, the reasonable parking line location away from the designed stopped line is about 6.0m, take parking 35% of top coal, greatly reduces the coal loss, recycles 59511t of top coal,creates more economic benefit of 2.9756 million; In theory, it is possible to take full recovery of top coal, the key is to make the support- surrounding rock system in the most stable space-time conditions. In the new designed stopped mining line position,the roof is in a stable state, and the static load is 0.89MPa. During the cutting retrace channel,the area of basic support,the support working resistance remains stable,the average is 0.89MPa. During the formal retracement, each support working resistance increases in different extent, but does not appear pressure surge phenomenon.