Stress and failure characteristics of full-length mortar anchored GFRP bolts under dynamic and static loads

In order to study failure problem of glass fiber reinforced plastics (GFRP) bolts under blasting dynamic load, this study establishes a numerical model of full-length mortar anchored GFRP bolt using FLAC(3D) software. The stress and failure characteristics of the bolt, bolt-mortar interface, and mortar-rock interface under pre-tension static load and blasting dynamic load are investigated, and the influences of dynamic load intensity, surrounding rock strength and mortar strength on bolt stress are analyzed. The reliability of the research results is verified in comparison with the existing experimental results. The results show that the maximum axial stress of GFRP bolt increases linearly with the increase of dynamic load intensity and decreases with the increase of surrounding rock or mortar strength, and the axial stress distribution of GFRP bolt is more concentrated than that of metal bolt. The shear stress of the two interfaces increases rapidly to the peak along the bolt, and then decreases to zero. After that, the interface with relatively weak bonding properties is debonded at first, and the shear stress at the debonding position decreases to the residual bond strength. Meanwhile, the peak shear stress shifts to the bottom of the hole. The shear stress distribution of GFRP bolt is more concentrated than that of metal bolt, and the peak position is more prominent. The greater the dynamic load intensity, the larger the debonding length and shear stress distribution of the failure interface, and the peak position of the shear stress of the undamaged interface will be transferred to the bottom of the hole. The greater the surrounding rock strength or the smaller the mortar strength, the more likely the shear failure occurs at the bolt-mortar interface; on the contrary, it is more likely to occur at the mortar-rock interface.