The axial response of fully grouted rock bolts using a distributed fiber optic sensor technique

ABSTRACT: The primary function of rock bolts is to stabilize the weakened ground around the periphery of the tunnel by transferring the load from the weakened rock to the more stable rock deeper into the rock mass. Through the use of a fiber optic sensor technology that has been developed by the authors, axial strain along the fully grouted rock bolt can be determined at a spatial resolution of 0.65 mm. This continuous strain monitoring technique provides comprehensive and unique insight into load transfer mechanism(s). This allows for in-depth geomechanical insight with respect to the behaviour of fully grouted rock bolts with a view to optimizing the performance of such rock support elements. In particular, this paper examines the effect of embedment length based on various simulated rock grout mixtures as well as specimen/rebar sizes. This paper summarizes the methodology employed for such laboratory testing of rock bolt (rebar), and provides results for a cement-grouted sample with an embedment length of 500 mm.