A method to evaluate regional stress state and Young's modulus by analyzing mining induced deformation of ground is proposed. Mining induced deformation is interpreted as the deformation due to the geometrical change of ground surface caused by mine activity and it is classified into two types, i.e., the displacement increment induced by the gravity and that by the horizontal regional strain. It is pointed out that both regional strain and Young's modulus can be estimated by analyzing the mining induced deformation, because the displacement induced by the regional strain is independent of the Young's modulus and the displacement induced by the gravity is in inversely proportional to the Young's modulus. The relative displacement arising from mine excavation in Torigatayama limestone mine, Japan have been measured by GPS. Both the stress state and Young's modulus of the regional field including the limestone mine were estimated by back-analysis using three dimensional finite element method. It is shown that the maximum principal direction of the regional stress is almost NE-SW and Young's modulus of the ground is between 3 and 6 GPa.
Deformation of rock mass arising from excavation is closely related to initial stress and elastic modulus as well as surface geometry or mining layout. Therefore, quantitative estimation of those is essential to understand deformation behaviors of the rock mass (MMIJ 2005). Especially, in the case of open pit mines, estimation of regional stress state and elastic constants of whole mining area is important since scales of mining area and cut slopes often become several km. In this study, a method to evaluate both regional stress and Young's modulus of ground by analyzing mining induced deformation is proposed. Then, its validity is verified by analyzing surface displacement measured by GPS in Torigatayama limestone mine.