Abstract
Based on the raw data of shield pressure and overlying strata movement measured in the field, the ground pressure features and overlying strata movement were analyzed in 8202 extra-thick coal seam longwall top coal caving working face of Tongxin coal mine after its extraction. The research results show that: during the process of mining, the interval of the lower sub key strata caved for the first time is 120 m, the periodic weighting interval ranges from 15 m to 30 m, with an average of 25 m. When the immediate roof is relatively thick, the fractured lower sub key strata can be hinged to form a stable “Voussoir Beam” structure, which makes the ground pressure not severe and the shield pressure small in the ends of the panel. When the immediate roof is thin, the arc triangular of the lower sub key strata in the ends of the panel loses mechanical contact to the caved immediate roof and assumes a “Cantilever Beam” structure, which makes the ground pressure severe and shield pressure large in the ends of the panel. Due to the large mining space of longwall top coal caving working face in extra-thick coal seam and big rotary angle of the overlying strata, the lower sub key strata can’t connect with each other to form a stable bearing structure, therefore, the shield pressure is a given load of roof rock, which results in a constant pressure of the shield.
Highlights
With the development of China’s coal mining technology, mine construction and coal mining toward large-scale, intensive direction of development trend, China’s extra-thick coal seam mining is an urgent need for high yield and efficiency of coal mining methods [1-4]
Most researches in China are concentrated in the aspects of working surface equipment, ground pressure control and mining method selection on the extra-thick coal seam
In the whole working face, the square deviation of the average of 38# shield pressure at the end of a cycle presents a big trend in the middle and both ends, indicating that the ground pressure in the middle of the working face is higher than the two ends
Summary
With the development of China’s coal mining technology, mine construction and coal mining toward large-scale, intensive direction of development trend, China’s extra-thick coal seam mining is an urgent need for high yield and efficiency of coal mining methods [1-4]. Compared with the traditional layered mining caving technology, longwall top coal caving (LTCC) is a good method to exploit the extrathick coal seam, with the high yield and high efficiency, low cost of roadway excavation rate, low cost of raw coal, strong adaptability and high safety [5-9]. Most researches in China are concentrated in the aspects of working surface equipment, ground pressure control and mining method selection on the extra-thick coal seam. Based on this, taking Tongxin coal mine 8202 LTCC working face as an example, research on extra-thick coal seam under gob caving roof strata movement and ground pressure features, in order to achieve the purpose of safe and efficient mining working face, provide a reference for the similar conditions of coal mining. Ma Zhanyuan et al.: Research on the Ground Pressure Features of Long Wall Top Coal Caving
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