DEVELOPMENT MECHANISM OF MINING-INDUCED GROUND FISSURE FOR SHALLOW BURIAL COAL SEAM IN THE MOUNTAINOUS AREA OF SOUTHWESTERN CHINA: A CASE STUDY

摘要

Mining-induced ground fissure (MIGF) contributes to vegetation deterioration, landslides and other natural hazards. The study is an attempt to reveal the development type, dynamic development process, and formation mechanism of MIGF for MIGF-induced natural hazard prevention of shallow burial coal seam mining. A novel approach including in situ measurement, theoretical analysis, and numerical simulation was implemented. There are two typical types of fissures, namely sliding-type ground fissures and stepped-type ground fissures. Sliding-type ground fissures generally develop in a mountainous slope with a large gradient while stepped-type ground fissures typically occur in a mountainous slope with a small gradient and especially near a valley. Dynamic development process of MIGF is significantly affected by roof periodic movement. The advancing distance of a sliding-type ground fissure is 1.35 times periodic weighting step distance while it corresponds to 0.89 times the periodic weighting step distance for a stepped-type ground fissure. A positive relationship exists between horizontal tensile deformation and MIGF width. The movement mode of "voussoir beam" is favorable for sliding-type ground fissure development while the movement mode of "stepped beam" leads to stepped-type ground fissure development. These results can contribute to MIGF treatment and ecological protection in the southwestern mountainous area.