Evaluation of Pull-out Test to Design Underground Coal Mine Support Systems for Depillaring Operations

Abstract

Roof bolts are active support systems used extensively in underground coal mines. It keeps on supporting the roof of the driven gallery and does not create any hindrance in the movement of man and machinery. Roof bolts have replaced completely the involvement of props, cogs, chocks, etc. used in earlier days during conventional underground coal mining methods. Mechanized depillaring, also, uses roof bolts as breaker lines while depillaring to control the encroachment of goaf during the caving of the overlying roof inside the goaf. Roof bolts are used in Indian underground coal mines as per usual assumptions based on trial-and-error methods. Generally, the pull-out test is carried out in Indian mining conditions as per the circular given by the DGMS to test the strength of installed bolts in underground coal mines supporting the roof of the gallery. Several studies have been carried out on the design of such support systems in earlier days. However, the design of such support systems based on these studies cannot be directly implemented due to the complexity and uniqueness of Indian geo-mining conditions. In this paper, an effort has been made to study the previously developed design of roof bolts through empirical, analytical, and numerical simulation techniques. This paper also presents a brief introduction about the pull-out test practices in underground coal mines with an attempt to simulate the behavior of bolts in underground coal mines on ANSYS software. Using the ANSYS numerical model for the pull-out test we have conducted various analyses to determine the parameters on which the performance of a roof bolt depends and tried to draw some conclusions based on our findings. It is decided to design the roof bolts soon based on validating the results of this numerical simulation for underground coal mines.