The deformation suppressing effect of mountain tunnel reinforcement works for deformed mountain tunnels in service are evaluated by numerical analysis. It is found that the back-filling has a limited effect by itself. It is found that the rock-bolting has the effect even by itself, and that the effect increases as the number of rock bolts increases, and there is a length that the effect does not increase any more, which is related to the size of the fracture region. It is found that the effect of the liner reinforcement is small by itself, but the effect becomes apparent when liner reinforcement is used in combination with the back-filling. It is considered that the liner reinforcement should be used in combination with the back-filling and the rock bolting, only when the deformation is large and large effect is required. Based on these results, the selection criteria of reinforcement work and the prediction method of reinforcement effect are proposed so that it can be applied in practice. Moreover, the validity of the method is confirmed by the verification analysis of the actual deformation tunnel.
Tunnel displacement monitoring, a common and mandatory practice amid tunnel excavation, has shown to provide valuable information for evaluating or predicting ground conditions near tunnel face as well as information for assisting decision-making to select and apply proper tunnel support system during excavation. This feature might serve well even for high overburden tunneling, where little geotechnical information could be available in advance of excavation. One of the advantages of extracting information from monitoring data is to predict final tunnel convergence from initial few displacement readings: finding relationships between the initial and the final displacement. In order to fully exploit the monitoring data, it is crucial to observe tunnel displacements in proper interval, locus, and especially, timing. Along with analyzing correlation between monitoring data and actual tunnel support behavior, this paper emphasizes the importance of most initial displacement monitoring, as well as presents renewed support application criteria specific to excavation of solid sedimentary rock masses with foliation or bedding structures. Tunneling experiences in the Akaishi mountain range, central Japan, have shown the validity of this analytical approach.