METHOD OF EXCAVATING TUNNEL

PURPOSE:To eliminate the need for taking refuge in blasting, and to increase the speed of excavation by excavating the upper half of a mountain tunnel, etc., to be excavated through the method of construction of pilot blasting and excavating a lower half through the method of construction of non-blasting excavation. CONSTITUTION:The upper half of a tunnel is excavated several hundred meters through the method of construction of upper-half pilot blasting. A slit is bored along the lower-half outer circumference of a tunnel design line by a slit drill 1a. Rock is crushed by a power splitter, and the biting of rock is broken to pieces through secondary crushing by a breaker, which are carried out to the outside of the tunnel. Accordingly, since blasting is not used for excavating the lower half of the tunnel, refuge is unnecessitated, and the term of works can be shortened while cost can be reduced and the safety of operation attained.