Study On Shear Behavior Of Rock Joint Strengthened With BFRP Bolt

As a new composite material,BFRP anchor has the characteristics of light weight,high strength and good corrosion resistance,which can replace the traditional reinforced anchor in the reinforcement of rock and soil.In this paper,the laboratory rock direct shear test and theoretical analysis method are used to study the shear performance of BFRP bolt reinforced rock joint surface.The influence of rock strength grade and anchoring angle on the shear performance of BFRP bolt in rock and soil is studied,and the calculation method of shear strength of joint surface with anchor is given.The main research contents and achievements are as follows:(1)The results of direct shear test show that the shear process of BFRP anchor joint surface can be divided into three stages: elastic stage,yield stage and failure stage.In the elastic stage,the axial force of the anchor basically does not contribute to the shear capacity of the joint surface.At this time,it is mainly the "pin effect" of the anchor rod that provides shear resistance;after entering the yield stage,the axial restraint effect of the anchor rod begins to gradually play a role,and the "pin effect" provides shear resistance together.(2)The sensitivity analysis of test parameters showed that although the harder rock system has greater shear stiffness than the softer rock system,which can effectively limit the relative displacement of the joint surface,the softer rock system can give full play to the shear capacity of the anchor and the reinforcement effect is more obvious.When the anchorage angle is 30 °,the anchorage effect of BFRP bars is better than HRB400 E bars.For the harder rock,the best anchoring angle is between 60° and 90°.For the softer rock,the reinforcement of the bolt always enhances the shear resistance of the joint surface.(3)The failure mode of shear BFRP bolt is summarized through the test.For the harder rock,it is expansion fracture under tension and shear force,and break off under compression and shear force.When anchorage angle is less than 90 °,the stress and deformation length of BFRP bolt will gradually increase with the increase of the anchoring angle and the peak shear force within the tensile range of the bolt,and the bending point will appear at 60 ° anchoring angle.Under the condition of 30 ° anchorage angle,the stress and deformation length of BFRP bolt and HRB400 E steel bar are basically the same.When the anchorage angle is 120 °,the BFRP bolt will have compression shear failure at the joint surface.For the softer rock,the deformation trend of bolt is similar to that of harder rock.(4)By introducing the Tsai-Hill strength criterion to judge the yield of BFRP bolt,a formula to calculate the shear strength of the joint surface of rock reinforced by BFRP bolt is obtained,and the relative error is less than 21.17% under the tensile state of bolt.