Numerical simulation of rockmass behavior around the shaft excavated by short-step method

Tani, Takuya*; Shimono, Masato*; Iwano, Masahiro*; Yamamoto, Takuya*; Yamazaki, Masanao; Sanada, Hiroyuki

During the construction of the Horonobe URL shaft, some measurements have been carried out to verify the design and construction method in sedimentary soft-rock. The results obtained from the in-situ measurements at the G.L.-121 m show the unique behavior of surrounding rock masses. This paper reports the result of the numerical simulation of the behavior around the shaft excavation by short step-method. In the analysis using axisymmetric elastic FEM model, construction procedure including the high stiffness lining concrete is accurately followed and the deformation behavior around the shaft is well simulated. Consequently it is found that the excavation release ratio in the short step excavation method is different from one in the typical NATM tunnel excavation.