ABSTRACT
This contribution assesses longer-term anchorage performance of fully grouted bolts in different lithologies in two coal mines in Illinois using the Short Encapsulation Pull Test (SEPT) studies. These tests were done at three different times after bolt installation; 0 days, 125–140 days, and 188–270 days. A borehole was also drilled in each test area about 2.6 m above the coal seam prior to bolts installation and examined with a borehole camera to document changes in de-laminations. Load cells monitored changes in few selected bolts. In addition to Grip Factor (GF), anchorage stiffness data for bolts were also developed that provided additional insights. GF values for all lithologies were similar to those reported in the literature. GF values typically increased with time but anchorage stiffness typically decreased. This was a significant finding affecting longer-term performance of bolts and ground control in coal mines in southern Illinois.
