The impact of key strata movement on ground pressure behaviour in the Datong coalfield

Abstract In-situ investigations are the most direct and authentic approach for determining the law of strata movement. In this study, in-situ investigation was carried out to determine the law of fracture and movement of a key stratum. Four-point surface extensometer (FPSE) inside overlying strata and borehole camera observation were used in the overlying strata of a fully mechanized caving face of a super-thick coal seam in the Datong coalfield. The time–space correspondence between the fracture and movement of the key stratum and ground pressure in stopes was established in combination with observations of the ground pressure of the working face. Results show that the primary key stratum of the overlying strata is the main controlling stratum and its fracture and movement are the underlying cause of strong ground pressure behaviours, such as rib spalling, roof fall, and support crushing. The findings suggest that the primary key stratum can be weakened, and the energy release can be decreased by hydraulic fracturing, deep hole blasting, and other measures, thus relieving ground pressure behaviour. The research method of establishing the time–space correspondence between fracture and movement of the key stratum and ground pressure behaviours based on in-situ investigation can provide guidance for mining engineering schemes, such as exploring master control strata with strong ground pressure behaviour under similar conditions and determining a reasonable capacity for the support.