**4. Materials design model**

610 Numerical Simulation – From Theory to Industry

Bearing plate

Shear force in wall rock

**Figure 3.** Bolt-Rock interaction model (after Peng and Guo, 1992)

Bolt head


behaviour properly, particularly at the contact interfaces.



110 kN and found that:

modelled in the elastic region.

interface and hinge point position.

*Stankus and Guo* (1996) investigated that in bedded and laminated strata, point anchor and fully grouted bolts are very effective, especially if quickly installed at high tension after excavation. They used three lengths 3300, 2400, and 1500 mm and three tensions, 66, 89, and

Tension in bolt

Reaction force bolt

Shear force in bolt


They developed a method for achieving the optimum beaming effect (OBE). However there were some assumptions in their methodology such as, the problem with the gap element, which is not flexible for any kind of mesh, especially with thin grout. Many relevant parameters about the contact interface cannot be defined in gap element. All materials were

*Marence and Swoboda* (1995) developed the Bolt Crossing Joint (BCJ) element that connects the elements on both sides of the shear joint. It has two nodes, one each side of the discontinuity. The model cannot predict the de-bonding length along the bolt, grout

It was realised that to further facilitate data analysis and the stress and strain build up along a bolt surrounded by composite material and their interaction, a powerful computer simulation was needed. FE modelling is considered to be the only tool able to accomplish this goal. There is still a lack of an adequate global models of grouted bolts to analyse bolt The FE method is the most suitable computational method to evaluate the real behaviour of the bolt, grout, and surrounding rock when there are composite materials with different interfaces. A three dimensional FE model of a reinforced structure subjected to shear loading was used to examine the behaviour of bolted rock joints. Three governing materials (steel, grout, and concrete) with two interfaces (bolt-grout and grout-concrete) were considered. To create the best possible mesh, symmetry rules should be applied. To reduce computing demand and time (when a fine mesh is used) the density of the mesh has been optimised during meshing. The division of zones into elements was such that the smallest elements were used where details of stress and displacement were required. The process of FE analysis is shown in Figure 4.
