Systematic Approach to Mitigate Longwall Subsidence Influences

The ground and surface subsidence process induced by longwall coal mining operations can cause adverse influences to subsurface and surface structures and water resources. Successful mitigation of these influences depends heavily on accurate assessment of the types, severities and locations of the subsidence-induced deformations and good knowledge of the structures. The most important step for mitigating subsidence influences is to accurately predict the dynamic and final movements and deformations in the area of interest. Based on the principle of influence function method, a series of subsidence prediction models have been developed for predicting dynamic and final surface and subsurface subsidence for longwall, room and pillar mining operations. The effects of inclined coal seam and steep surface terrains can also be considered the subsidence prediction. These prediction models have been validated with a large number of collected subsidence cases. With the accurately predicted ground deformations and good knowledge of structures, the types and severities of possible subsidence disturbances to the structures can be correctly assessed. For large and complicated structures, subsidence influences on structural stability, integrity and functionality have to be carefully considered. Once the causes and extents of the structural disturbances are identified, designing proper and cost-effective mitigation measures is often relatively easy. This systematic prediction-assessment-mitigation approach has been successfully employed in numerous applications.