ORIGINAL PAPER Experimental and 3D Numerical Simulation of Reinforced Shear Joints Hossein Jalalifar Æ N. Aziz Received: 5 August 2008 / Accepted: 12 January 2009 / Published online: 10 February 2009 Ó Springer-Verlag 2009 Abstract The load transfer capacity and failure mecha- nism of a fully grouted bolt installed across a joint in shear is investigated, both experimentally and numerically, in ﬁve types of bolt. The double-shearing testing of bolts were studied in concrete blocks of 20, 40 and 100 MPa strengths, subjected to different pretension loads of 0, 5, 10, 20, 50 and 80 KN, respectively. The parameters examined include: shear resistance, shear displacement, induced strains and stresses during the bolt-bending pro- cess, and its ultimate failure across the sheared joint planes. The conclusions drawn from the study were that the strength of the concrete, bolt proﬁle conﬁguration and bolt pretension load played a signiﬁcant inﬂuence on the shear resistance, shear displacement and failure mechanism of the reinforced medium. Experimental and numerical sim- ulations showed that the failure occurs as a result of the induced axial and shear stresses acting between the hinge point distances in the vicinity of the shear joint plane. Keywords Bolt failure  Load transfer  Bolt bending  Grouted bolt  Numerical modelling 1 Introduction Rock bolts are one of the most popular systems of support in underground mining, tunnelling and in a variety of civil engineering operations. Speed, effectiveness, minimum installation space and cost are some factors that have contributed to the increasing acceptance of bolting as a favourable ground support system. The effectiveness of a support system is dependent upon a better understanding of the load transfer mechanism between the rock-resin and bolt interaction, particularly across the joints and share planes that the bolt intersects. Factors inﬂuencing the shear resistance across joints are; bolt diameter, hole diameter, steel quality, bolt extension, conﬁning pressure, strength of the rock and the strength of the grout. Signiﬁcant progress has been made both by experimental studies and numerical simulations with regard to the mechanical behaviour of bolted rock joints. Much of the theoretical studies under- taken were made using both the ﬁnite element and ﬁnite difference methods. The ﬁrst systematic research on fully grouted rock bolts was conducted on bolts embedded in blocks of granite (Bjurstrom 1974). The failure mode, strength and deformation stiffness of the sheared bolted joints were found to be dependent on the bolt angle of installation across the joint. Laboratory tests on the shear resistance of bolted joints, using various materials, found that the failure of the bolt was caused by the combination of axial and shear forces (Dight 1982). The normal stress acting on the joint surface had no inﬂuence on the shear resistance and joints with inclined bolts were stiffer than the perpendicular ones. Joint surface friction, bolt inclina- tion and the degree of rock and grout deformability are also the major inﬂuencing parameters on joint shear strength and bolt contribution. Ferrero (1995) found that the overall strength of the reinforced joint was attributed to the com- bination of both the dowel effect and the incremental axial force increase due to bolt deformation. A shear strength model for reinforced rock joints was proposed, based on the numerical modelling and laboratory tests, which sug- gested a modiﬁed analytical model for bolts installed H. Jalalifar (&) Shahid Bahonar University of Kerman, Kerman, Iran e-mail: jalalyfar@yahoo.com N. Aziz Wollongong University, Wollongong, Australia 123 Rock Mech Rock Eng (2010) 43:95–103 DOI 10.1007/s00603-009-0031-7