Study On Structure Characteristics Of Overlying Strata In Shallow Coal Seam Under Longwall Mining

Aiming at the actural situation of shallow coal seam mining in ordos region, relying firmly on the subject of overlying strata structure characteristics and based on the geological survey for shallow coal seam and the mine pressure observation in the experiment face, the thesis analyzed the forms and movement characteristic of overlying strata structure and investigated the key factors on overlying strata structure stabily in shallow coal seam through the method that combined theory analysis with computer numerical simulation. Combining with the mining practice of 1203 and 20601 faces in daliuta mine, the project proof analysis was carried out at last.The conlusions indicated that whether the pressure arch structure could form in the overlying strata of shallow coal seam under longwall mining and keep the structure stable was the key factor on shallow coal seam definition. The key influencing factors on shallow coal seam mine pressure and overlying strata structure stability were mining height and face length. The critical height of "pressure arch" structure in overlying strata would be different under the mining condition of different mining height and different face length. The face length plays a greater impact on overlying strata structure stability too. But after the face length reached a certain value, the increase of face length would not make greater imparct on structure stability. When the mining height reached a certain value, the "pressure arch" structure would not form in overlying strata. The definition of shallow coal seam was conditional and relative. A coal seam under the certain face length and mining height may belong to the shallow coal seam, when the face length and mining height changed, it may no longer belong to. The crux was lay on the basic characteristics and stability situation of "pressure arch" structure in overlying strata under different promoting stage of the working face, namely whether the stable and dynamic "pressure arch" structure could form in overlying strata. The above conclusions was proved by the mining practice of 1203 and 20601 faces in Daliuta mine, and provided a certain example for mining methods selection and solving problems in the production technology and security issues of shallow coal seam mining in Ordos region.