AXIAL LOAD DISTRIBUTION OF ROCK BOLTS WITH PLASTIC GROUND PRESSURE AFTER TUNNEL COMPLETION

Abstract

 Tunnels in weak rock may be subjected to plastic ground pressure not only during tunnel excavation but also after completion, resulting in deformations such as side wall displacement. At this time, although the rock bolts are installed and the axial load is sometimes measured, there has not been sufficient discussion on how to evaluate the axial load measurement results of the rock bolts after tunnel completion. Therefore, the authors investigated the axial load distribution of rock bolts by numerical analysis, targeting rock bolts used as reinforcement work for tunnels that are subjected to plastic ground pressure after completion. Through this investigation, the authors present four distinct scenarios: ineffective rock bolts, insufficient length, yielding, and decoupling. They also provide examples of axial load distribution. Furthermore, the measured data of rock bolt axial load in actual tunnels were evaluated, confirming the usefulness of the insights obtained in this study for the assessment of axial load measurement results.