Abstract
Fully grouted rock bolts are widely used in civil engineering and mining engineering, playing a significant role in keeping the stability and safety of excavations. In this paper, the load transfer mechanism of fully grouted rock bolts was studied with an analytical model. A trilinear model was used to depict the bond‐slip behaviour of the bolt/grout interface. The displacement of the confining medium was involved in this analytical model. Then, the shear stress propagation along the bolt/grout interface was analysed in the elastic, elastic‐softening, elastic‐softening‐debonding, softening‐debonding, and debonding stages. Experimental pull‐out tests were used to validate this analytical model. There was a good correlation between experimental and analytical results. A parametric study was conducted to evaluate the influence of Young’s modulus of the confining medium, the shear strength of the bolt/grout interface, and the residual shear strength of the bolt/grout interface on the load transfer performance of rock bolts. The results show that increasing Young’s modulus of the confining medium was beneficial for improving the load transfer performance of rock bolts. However, once Young’s modulus of the confining medium was beyond a critical limit, it had marginal effect on the peak load of rock bolts. Furthermore, increasing the shear strength of the bolt/grout interface and the residual shear strength of the bolt/grout interface led to rising of the peak load of rock bolts. However, compared with the residual shear strength of the bolt/grout interface, increasing the shear strength of the bolt/grout interface had more apparent effect in improving the peak load of rock bolts.
Highlights
A rock bolt is a rock tendon which can be either a rod or a strand, installed in a borehole to reinforce the surrounding rock mass and soil [1]
To better understand the performance of the reinforcement system, ompson et al [10] classified the rock reinforcement system as three types: continuously mechanically coupled (CMC), continuously frictionally coupled (CFC), and discrete mechanically or frictionally coupled (DMFC). is study deals with fully grouted rock bolts, and based on this classification, fully grouted rock bolts belong to the CMC system
Since this study aims at studying the bond failure of the bolt/grout interface, the grout/medium interface was assumed to be intact in the pull-out process of rock bolts. en, τp τ τr δp δr δ the shear slippage of the bolt/grout interface was defined as the relative movement between the rock bolt and the confining medium [53, 54]: δ(x) ub(x) − um(x), (2)
Summary
A rock bolt is a rock tendon which can be either a rod or a strand, installed in a borehole to reinforce the surrounding rock mass and soil [1]. Numerous field applications and computer simulation have proved that rock bolts play a significant role in improving the internal strength of rock mass and enhancing the safety of underground excavations [3,4,5,6]. E rock bolt reinforcement system is basically composed of four components: the surrounding confining medium, e.g., rocks or soils, the rock reinforcement element, the internal fixture, and the external fixture [7,8,9]. For the CMC system, cementitious grout or polyester resin can be used to bond rock bolts with the surrounding confining medium [11,12,13]. This paper focused on the axial performance of rock bolts
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