Estimation of regional stress state and Young's modulus by back analysis of mining-induced deformation

A method to evaluate regional stress state and Young's modulus by analyzing the mining-induced deformation of ground is proposed. The effect of changes in regional strain state due to tectonic plate motion can be accounted for using the proposed method. Mining-induced deformation can manifest itself as changes in ground surface geometry resulting from mining activity. There are three underlying factors that can contribute to the deformation, these being: displacement induced by the effect of gravity; displacement induced by the effect of horizontal regional strain; and, incremental change in the horizontal regional strain. Both regional strain and Young's modulus can be simultaneously estimated, because the displacement induced by the regional strain is independent of the Young's modulus and the displacement induced by the gravity is inversely proportional to the Young's modulus. The relative displacement arising from the mining excavation at the Torigatayama limestone mine in Japan has been measured by GPS. Both the regional stress state and Young's modulus were estimated by back analysis of the relative displacement using a 3-D finite element method. It was shown that back analysis based on changes in distance between the measurement points provides a more reliable estimation than that could be achieved based on the direct relative displacement.