Influence of Grout Properties on the Tensile Performance of Rockbolts Based on Modified Cable Elements

The grout annulus (GA) has a significant effect on the tensile performance of rockbolts in mining engineering. However, little research has been conducted to use modified cable elements to study this effect quantitatively. This paper used the modified cable elements in FLAC3D to study the effect of the GA on the tensile performance of rockbolts. The two-stage coupling law was used to simulate the behaviour of the GA. The stress had a linear relation with the slippage before the shear strength (SS). After the SS, the stress decreased exponentially. Numerical in situ roadway reinforcement cases were used to study the influence of the grout annulus on the tensile performance of rockbolts. The results showed that, when the SS of the GA increased from 3.2 MPa to 6.4 Mpa, the peak force of rockbolts increased from 247 kN to 425 kN. Moreover, when the SS of the GA increased from 3.2 Mpa to 6.4 Mpa, the distance between the position of the maximum tensile capacity and the external end decreased from 1.17 m to 0.81 m. Last, for the circular roadway, the peak force in rockbolts installed in the lateral side was 171.7 kN, which was significantly larger than the top side of 72.3 kN.