Investigation on the mechanical behavior and failure characteristics of fully grouted bolts under tension

Abstract

ABSTRACT A better understanding of the mechanical behavior and failure characteristics of fully grouted bolts under tension is of great significance to ensure the safe production of coal mines. For this purpose, a pull-out experiment of anchorage specimens was conducted and a numerical simulation was conducted based on the experimental results. The experimental and numerical results were analyzed in detail to study the bearing characteristics of fully grouted bolts. The results indicated the following: (1) The bearing characteristics of the anchorage interface could be divided into four stages. The local strain of the anchorage interface was positively correlated with the change trend of the pull-out load. (2) The acoustic emission (AE) activity showed a tendency to first increase and then decrease during the pull-out process. The cumulative AE energy was the largest in the microcrack development stage, while the cumulative AE counts and AE hits were the largest in the shear failure stage. The AE peak frequency presented obvious divisional centralized distribution characteristics, and the AE amplitudes were mainly in the range of 50–80 dB. The cumulative AE events were positively correlated with the damage degree of the anchorage interface and the duration of AE events increased significantly during the microcrack development stage. (3) There are four main stages in the pull-out bearing process of fully grouted bolts. The failure process of the fully grouted bolts was progressive. The increase of the bonding length not only increased the non-uniformity of the shear stress of the anchorage interface, but it also affected the characteristics of the pull-out load-displacement characteristics. With the increase of the bonding length, the peak pull-out load first increased rapidly and then increased at a relatively low but steady rate. The research results may provide guidance for the support design of fully grouted bolts.