Abstract
Shotcrete-and-rockbolts method (NATM) has been adopted around the bottom section of a large vertical ventilation shaft. It connects two horizontal tunnels and makes complex shape in this section. In this paper we have introduced a design method of NATM using three-dimensional FEM analysis and in-situ test and a method of field measurements in a shaft. According to the result of field measurement we have examined about a reliability of the design method and have discussed about a difference of support mechanism between short-step method and NATM, a distinctive deformation mechanism around a shaft and a specific behavior of ground around connecting section of the shaft.
