Experimental Study On Bolting Effect Of Bolted Joint Rock Masses Considering Bolt Strength

The strength of bolt is mainly affected by its diameter and material (tensile strength). The strength of bolt is very important to improve the shear resistance of bolted joint rock masses. The shear test of bolted joint was carried out. The influence of bolt strength on the shear deformation characteristics and bolting effect of bolted joint was studied. The calculation model of shear resistance of bolted joint considering bolt strength was proposed, and the contribution of axial force and shear force of bolt to shear resistance of joint under different bolt strength was analyzed. The results show that:(1) With the increase of the bolt diameter, the peak shear resistance of the bolted joint increases linearly. When the bolt diameter exceeds a certain critical value, it will play a bolting role. The greater the tensile strength of the bolt, the smaller the critical value. (2) With the increase of the diameter and tensile strength of the bolt, the plastic hinge of the bolt moves outward, the length of the deformation section increases, the ability of the bolt to resist deformation and failure is enhanced, and the shear resistance of the joint is enhanced. (3) The shear process of jointed joint can be divided into four stages: elasticity, yield, strengthening and residual. In the elastic and yield stages, the bolt mainly plays the role of pins. The contribution of the bolt is positively correlated with the tensile strength of the bolt, and the relationship with the bolt diameter is affected by the thickness of the anchoring agent. In the strengthening stage, the bolt forms a plastic hinge, and the contribution of the bolt is provided by the shear resistance and axial force of the bolt, which is positively correlated with the tensile strength and bolt diameter. In the residual stage, the bolt fracture does not provide shear resistance. (4) Based on the large deformation theory of bolt, the anti-shear force model of bolted joint considering the strength of bolt is proposed. The analysis shows that with the increase of bolt diameter and tensile strength, the proportion of axial force contribution of bolt increases, and the proportion of shear force contribution of bolt decreases.