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The reinforcement effect of rock bolts in granular mixtures is studied by the mesoscopic numerical simulation method. The granular mixtures consist of 3D polyhedral granules. The particle size distribution (PSD) is based on stochastic simulation technology. Simulations of rock bolts and granular mixtures are conducted by ABAQUS/Explicit program. The bolted granular material is analysed in macroscopic and mesoscopic scales. Various factors on the mechanical properties of the granular mixture are studied, including spacing, PSD, the prestress, porosity of the granular material, the length of the bolts and the diameter of supporting plates at the bolt ends. The simulated results reflect the deformation and reinforcement effect of different bolted granular structures. The macroscopic results are closely related to the evolution of the mesoscopic fabric. Without considering the bolt length, if the bolt spacing is less than three times the average particle diameter, a stable structure can be formed using the rock bolts. Based on the samples in this paper, the list of ranking of importance of parameters on the degree of reinforcement is porosity > granule size > bolt spacing > supporting plate diameter > bolt prestress > bolt length. [ABSTRACT FROM AUTHOR]

Developing predictive models for quantitative assessment of the deterioration of rock bolts exposed to corrosive environments is essential for rational planning of maintenance activities for anchorage structures. This article presents a probability-based computational model for predicting the time-dependent deterioration of bond capacity of corroding rock bolts due to the attack of chlorides. The inherent stochastic nature involved in the corrosion and degradation process is identified and simulated. A method is developed based on fundamental Mohr–Coulomb theory to evaluate the effect of corrosion on the bond strength due to a failure mode involving splitting of grout cover. Parameters affecting both strength and stress state at the bolt–grout interface are quantitatively related to the degree of corrosion. Integrating the realised corrosion stochastic process and the developed bond loss evaluation method, a computational algorithm based on Monte Carlo simulation is presented for evaluating the bond deterioration in a probabilistic framework. The presented model is used in an illustrative example to show its capability to trace the evolution, throughout the entire design life, of several representative performance indicators of rock bolts as a structure unit or of the interested location within the anchor length. [ABSTRACT FROM AUTHOR]

Rock bolt is a major reinforcement technique for roadways in coal mines in China. Generally, separation of the bonding interface between the rock mass and the bolt may lead to collapse of the bolted rock mass due to stress concentration. In order to establish the stress concentration mechanism on the bonding interface, the distribution functions for shear stress and longitudinal force on the interface are derived using Mindlin's model, and a failure criterion for the interface is proposed. In addition, influencing factors for the stress distribution mode are identified. Both analytical study and numerical simulations by ANSYS have shown that, as the elastic modulus of rock increases, both shear stress and the longitudinal force-concentrating zone move towards the outer end of bolt and decrease gradually from the free surface to the rock mass body. Also, there is an optimizing cement thickness which results in relatively uniform distributions of shear stress and longitudinal force on the interface. It is valuable to investigate the bolt invalidity mechanism as well as reinforcement safety estimation in underground rock engineering design. [ABSTRACT FROM AUTHOR]