In the diagram opposite, mining of a longwall panel results in the formation of front and side abutment pressures. The peak of the front abutment pressures can occur 1 to 3 metres ahead of the face and the extent of the front abutment pressures can be up to 50 metres and more ahead of the face. Similarly, side (flank) abutment pressures occur on the adjacent barrier pillars as shown. The new stress ditribution resulting from the excavation is particularly important if it is likely to cause excessive ground deformation, contributing to difficult mining operation environments. In order to estimate the stress distribution, various emperical and other estimation methods are used, refer to the list of references for further reading.