ABSTRACT
On the basis of 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 mining the interval of the lower sub-key strata caved for the first time is 120 m, and the periodic weighting interval ranges from 15 to 30 m, with an average of 25 m. Because of the large mining space of longwall top coal caving working face in extra-thick coal seam and the large rotary angle of the overlying strata, the lower sub-key strata cannot 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.
