Structural parameters and critical anchorage length of tunnel system bolts made of basalt fibre

Abstract

Basalt fibre reinforced polymer (BFRP) has the advantages of high tensile strength and good durability; therefore, the anchor bolt developed with BFRP has potential application in tunnel surrounding rock anchorage. This study used meso-scale numerical simulation and laboratory tests to examine the structural parameters of BFRP anchor plate and rod and the critical anchorage length of BFRP cement mortar anchor. The results showed that: 1) the special-shaped truncated cone type anchor plate can convert the axial force into internal tensile stress, which improves the tensile performance of the basalt fibre material. 2) The larger the thread pitch of the BFRP bolt or the smaller the thread height, the more uniform is the shear stress distribution of the bolt thread, and the smaller is the maximum shear stress of the rod and nut. 3) The thread height of 2 mm and thread pitch of 18 mm is the optimal combination. 4) The critical anchoring length of the BFRP cement mortar bolt is 20–40 times its diameter. The findings of this study can provide new and meaningful reference for the application of System Bolts made of Basalt Fiber in tunnel engineering.