2021 Volume 77 Issue 1 Pages 17-31
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.