A case study on mining-induced horizontal shear deformation at the ground surface

Mining-induced horizontal shear deformation has not been commonly considered in subsidence engineering and risk management practices. This situation is different from many other engineering disciplines. Based on the results of field observations and analysis of 3D survey data from 20 longwalls in the Hunter, Newcastle, Western and Southern Coalfields of NSW, this paper presents evidence suggesting that mining-induced horizontal shear is a significant deformation mode that may affect a range of surface features. For civil structures, mining-induced horizontal shear is as significant as the conventionally defined horizontal strains, especially in areas with deep cover depths. This paper presents an argument that conventional subsidence parameters specifying horizontal deformations, in particular, horizontal strains, are inadequate for subsidence engineering and risk management purposes. A Shear Index is suggested to facilitate studies of mining-induced shear deformation at the ground surface.