Civil Engineering & Construction

1 Measurement of Steel Pipe Behavior in the Extremely Long Pre-Supporting Method (ELPS) During Tunnel Excavation

This case study involved the installation of approximately 45 m long steel pipes using the Extremely Long Pre-Supporting Method (ELPS) in weak ground near the portal of the Miyama Tunnel in Japan. Four optical fiber sensing lines were integrated into the steel pipes along their longitudinal direction at the top, bottom, left, and right positions, enabling continuous measurement of tensile and compressive behavior in both the vertical and horizontal directions. The acquired data were visualized as contour maps, clearly showing the location, extent, and changes in strain from ahead of the tunnel face to the excavated section behind it. This enabled a three-dimensional evaluation of the effective range and affected area of the long steel pipes.

The measurement results showed that bending compression began to occur in the steel pipes approximately 5 to 6 m ahead of the tunnel face, while significant deflection occurred within approximately 2 m behind the face immediately after excavation. These measurements clearly captured detailed changes in internal forces that were difficult to identify using conventional measurement methods.

2 Monitoring of a Water Transmission Pipeline and Surrounding Conditions (Joint Research with Hanshin Water Supply Authority and Kobe University)