ABSTRACT
Displacement monitoring allows us to evaluate the adequacy of applied tunnel support as well as to select and install suitable support proactively during excavation. The monitoring also helps us to examine the ground conditions adjacent to an advancing tunnel face. A 4.2-km-long tunnel, Hirogawara adit, with a maximum depth of 860 meters, was excavated in the Akaishi Mountains of central Japan. Correlation between the initial and final displacement was confirmed as monitoring data were accumulated concurrently with ongoing excavation. Then, the final displacement was predicted from the initial displacement readings, which led to the proactive application of optimum rock supports. Meanwhile, the monitored displacement showed characteristically anisotropic or asymmetric patterns of tunnel deformation: the larger horizontal strain than the vertical one, the larger displacement of the right sidewall than the left one. The monitored displacements as well as observed unilateral deformations indicated the possible presence of anisotropic ground conditions.
