Connective fracturing

A proper understanding of mining induced fractures in overburden strata during advancement of longwall faces is essential to estimate the change in permeability on the overburden strata. This understanding provides an assessment of water inrush potential and the impact of mining on ground and surface water systems. The height of fracture network stages, phases and developments are mostly site specific and governed by lithology of the mine site. The different stages and phases of fracture development may be similar among most of the mine sites, but may vary in intensity. The development of connective fractures results in increased permeability of roof and floor strata, hence an enhanced rate of groundwater pressure drops can be witnessed. A comprehensive numerical study could be a suitable tool to classify various zones of fractures above the underground extractions.

Similarly, the figures below show one of the case studies where the development of connected fractures and changes in permeability above the excavation are predicted using advanced numerical techniques.

Development of connected fractures (left) and changes in permeability (right, dotted line shows the initial permeability and solid line shows the final permeability) during underground longwall extraction.