A study on mechanical behaviors of concrete lining and rock caused by shaft sinking at the Horonobe underground research laboratory

In this paper, the authors discuss circumferential stress distribution in a concrete lining and displacement of rock around shaft wall induced by shaft excavation at Horonobe Underground Research Laboratory. Field measurements of the lining stress and rock displacement were conducted between 218m and 220m in depths during excavation of a 6.5m diameter access shaft and the results were analyzed using a three-dimensional numerical model. As a result, it was found that the maximum and minimum stresses occurred in the direction of horizontal minimum and maximum initial stresses, respectively. It was also clarified that difference in the stress between the maximum and minimum values was beyond 10MPa. In addition, it was found that compressive axial strain occurred around a shaft wall after casting concrete lining since rock behavior in the vicinity of shaft wall was controlled by a concrete lining.