Shear of bolted non-persistent joints: role of bolting conditions and joint persistency

Abstract

The instability of rock slopes and underground engineering is usually caused by the shear failure of non-persistent joints. Rock bolt, as the main support method, has an important influence on the shear behaviour of joints. However, the shear behaviour of bolted non-persistent joints has rarely been studied. In this research study, direct shear tests were carried out to explore the effect of different bolting schemes on shear behaviour of non-persistent joints. The test results showed that fully encapsulated bolts can greatly improve the shear strength of non-persistent joints, while end encapsulated bolts behave better at a larger shear displacement. The bolt breakage is closely related to the shear failure of non-persistent joints. The bolt passing through the coplanar coalescence areas usually has a larger shear deformation and breaks first. The shear displacement of bolt breakage tends to be smaller as the joint persistency decreases. Furthermore, acoustic emission tests showed that the fully encapsulated bolt noticeably reduced the shear damage, while it increased the shear failure intensity. In addition, the bolting effect tends to be smaller under a larger joint persistency.