The 4th International Symposium on Mine Safety Science and Engineering (ISMSSE2018)

221 / 2018-07-15 20:53:52

Numerical modelling approach on longwall mining-induced strata behavior by considering the fracture- weakening effect on rock mass

Longwall mining,Numerical simulation,Tension weakening,Fractures,Goaf consolidation

Mine Dynamics Disaster > roof

By employing the longwall mining method, a series of intensive strata responses and activities will be induced including stress redistribution, fracture extension and strata movement. Due to the geological stratification feature of coal mine strata, tensile failure and tension-induced fracturing play dominant roles in strata of the fractured zone, which brings the necessity of considering the weakening effect on rock mass behavior due to failure and fracturing in tension. In this presented study, a numerical modelling approach on mining-induced strata behaviors is proposed by considering the mechanical behaviors of caved zone consolidation and tension-induced weakening in fractured zone. Based on a numerical model built according to a study site, a parametric study with respect to different fracturing intensity parameters is carried out to investigate the fracturing weakening effect on mining-induced stress redistribution and strata movement. The numerical results show that, the tensile fracture intensity has notable effect on the mining-induced stress distribution in two aspects: (1) increase in the peak and area of the front abutment stress; (2) variation in the patterns of stress recovery in goaf. The stress data obtained from numerical simulation represent and back-analyze the behaviors (failure, movement) of overlying strata. High stress on the coal seam indicates the strata lie on and transfer loads to the seam, while low stress indicates detachment between the seam and suspending strata. With the increase in fracture intensity, the roof strata are more prone to breaking and caving, the suspending length of roof beam will reduce, which leads to the strata sufficiently break, cave and transfer overburden load to loose rock in goaf, and caving along the strike direction of panel becomes the dominant overlying strata movement, while the dominant movement is caving along the dip direction in the case of strong and intact overlying strata with few tensile fracture. Thus the tensile fracturing intensity is a factor that should not be ignored in studies that related to behaviors of overlying strata. Validated by analytical studies, the study presents a novel numerical modelling approach provides for this very topic and can be utilized for multiple researches on the basis of proper roof fracturing estimation or back analysis.