Principle, realization and analysis of roadway support effect of bolt element based on parallel computing system of strata motion

Abstract

A kind of bolt element was introduced into the self-developed parallel computing system of strata motion (based on the combined Lagrangian-discrete element method) applicable for modeling the transformation from the continuum medium to the discontinuum medium or the further evolution of the discontinuum medium, reflecting axial and shear deformations, and formed a bolt module. A bolt element is composed of two bolt nodes and a component between them. The essence of the bolt element is that in each overlay the position of a bolt node relative to the sub-element remains unchanged. A quadrilateral element is divided into two pairs of triangular sub-elements in two ways. Each is called an overlay. The control loop of the system was executed serially on the CPU and the compute-intensive tasks were off-loaded to the GPU. The bolt module is executed in parallel with other modules to obtain a higher computational efficiency. Evolution of the axial force of the bolt element at different positions was investigated through the pull-out test. Results show that the axial forces of bolt elements within a certain distance away from the drawing end rise in an oscillation mode as the displacement increases in the drawing end, which is explained from the view of the action of the surrounding rock on the bolt. The present distribution of the axial force of the bolt was compared with the theoretical solution based on the Mindlin’s solution of the displacement to check the correctness. In order to investigate the supporting effects of bolt elements, a mechanical model was established by taking a track roadway in the Juye Mine as the background, the deformation-cracking-motion processes of surrounding rocks of the roadway with bolt supports and without were obtained. Results show that the bolt elements have a good effect in preventing the deformation of surrounding rocks of the roadway, controlling the developments of cracks, and improving stress distributions. It is due to the fact that the increase of the confining pressure of surrounding rocks within the lengths of bolts leads to the increase of the bearing capacity of surrounding rocks. The present results with bolt supports are more realistic than those of the traditional continuous method, which is due to the fact that obvious cracks between the rock elements in the failure zone near the roadway occur, causing a certain expansion of surrounding rocks.

Keywords

• bolt element
• surrounding rock of the roadway
• continuous-discontinuous method
• supporting effect
• parallel computing