Investigating Earth Reaction to Pull-Out Process of Frictional Rock Bolts Using Distinct Element Method

Mohammad Sadegh Ayyoobi,Arash Refahi

doi:10.4236/ojg.2020.108038

Abstract

The reaction of earth to pull-out process of frictional rock bolts was here modeled by the distinct element method (DEM). Ten frictional bolts were prepared; the expanding shells of five bolts included convex edges and the others had the shells with concave bits. The strength of bolts was measured by applying a standard pull-out test; the results confirmed that the strength of shells with convex edges was remarkably more than the strength of other shells. Furthermore, a two-dimensional DEM model of the test was developed by a particle flow code; the obtained results showed that the reaction of rock particles to the contacts occurring between the convex edges and earth was considerably more than those of the concave bits. In the other words, the convex edges transferred the pull-out force into a large area of the surrounded rock, causing these bolts to have the highest resistance against earth movements.

Highlights

In order to increase the stability of rock structures, rock bolt systems have been developed dramatically for 50 years; they were designed for variety ranges of underground spaces and ground slopes
A two-dimensional distinct element method (DEM) model of the test was developed by a particle flow code; the obtained results showed that the reaction of rock particles to the contacts occurring between the convex edges and earth was considerably more than those of the concave bits
The pull-out strength of ten frictional rock bolts with expanding shells was investigated in the laboratory and modeled using distinct element method

Summary

Introduction

In order to increase the stability of rock structures, rock bolt systems have been developed dramatically for 50 years; they were designed for variety ranges of underground spaces and ground slopes. The performance of expansion-shell-rock bolts was investigated numerically. These bolts that belong to frictional categories make contacts with hole walls by expanding steel shells that include convex edges or concave bits, as shown in Figure 1 [8]. For this purpose, a standard pull-out test has been applied to the installed bolts, and reactions of earth to the pull-out process of bolts were modeling numerically by distinct element method (DEM). To verify the obtained results, the pull-out strengths acquired from DEM modeling were compared to those estimated from the experimental tests [13] [14] [15] [16]

Materials and Methods

Distinct Element Method

DEM Model of Concrete

DEM Model of Rock Bolts

Conclusion