Analysis and Evaluation of Pull-Out Load obtained from In-Situ Pull-Out Test for Fully Grouted Rock Bolt

Abstract

This study pointed out the two defects related with evaluation method of rock bolt pull-­out load and investigated the effects of the ground conditions and of w/c ratio changes caused by water inflow on rock bolt pull-out load through numerical analysis method. First, one defect is that the pullout strength of the rock bolts for the same results varies greatly depending on the researchers. To complement interpretation curve method, the report suggested three interpretation methods(log(P)-log(S), S­-log(t), P-△S/△log(t) methods). A validity of the newly proposed methods was verified based on results of the In­-situ rock bolt pull out test data on rock bolt installed on the rock with ground grades 3 to 5. The other defect is that an average of the results from just three pilot tests of rock bolt is considered to be the pull­-out load of the rock bolt. However, it is difficult to consider many parameters that affect the rock bolt pull-­load within just three times pilot test. So, this paper suggested that how to improve the accuracy of pull-out strength about the pilot test. Lastly, this report indicated the effects of w/c ratio and ground conditions (Ground grades 1­~5) to the load of rock bolt by using FLAC-­2D.