Practical use of initial displacement monitoring for predicting support behavior with asymmetric deformation in deep tunnel

Displacement monitoring provides essential information for safe and rational tunnel excavation. The data obtained allow engineers to analyze and predict tunnel behavior, facilitating the selection of appropriate supports and the evaluation of their effectiveness. In a recent tunnelling project in the Akaishi Mountains of central Japan, displacement monitoring was intensively implemented to ensure the stability of the 4.2-km-long Hirogawara adit, excavated to a maximum depth of 832 m. Analysis revealed a strong correlation between initial and final displacements. However, the tunnel experienced occasional support deformations. To address this, the trend of 3D absolute displacements was analyzed to predict and evaluate asymmetric deformation. The effective use of 1-cycle displacement monitoring proved critical for predicting final displacements and optimizing rock supports, particularly in cases with high overburden and limited geotechnical information.