Study of the evolution of mining-induced fractures with longwall face proceeds-insight from physical and numerical modeling

Understanding the evolution of mining-induced fractures with longwall face proceeds is of great importance to coalbed methane drainage and gas control. In this study,physical modeling and numerical simulation methods are used to study the evolution of mining-induced fractures with longwall face proceeding under the condition of three-dimensional space and time. It is found that mining-induced fractures within a given domain of overlying strata above the near gob center changes in a distinct way in contrast to a domain close to the entries. The fracture volume of a given domain in the overlying strata above the gob center show a rapid increase-decreasingsteady change pattern as the longwall face approaches and passes by,comparing to a rapid increase-steady change pattern of a domain close to the entries. Mining-induced fractures are most fully developed in the overlying strata that are away from the cut face and near the entries. Under the condition of the maximum horizontal stress parallel to the direction of the longwall panel,the development of mining-induced fractures is significantly higher than that under the condition of the maximum horizontal stress vertical to the direction of the longwall panel. A stronger immediate roof has a positive effect on increasing the permeability of mining-induced fractures.