Influence of Anchor Depth and Friction Coefficient Between Anchor and Rock on the Trajectory of Rock Masses Detachment

This work presents the results of a FEA (Finite Element Analysis) concerning the propagation of the fracture trajectory during the detachment of rock masses. The analysis considers mechanical anchoring parameters, including the depth of anchoring and the friction between the anchor head and the brittle material. The analysis involved varying the effective anchorage depth h(ef) = 50, 100, and 150 mm, along with considering different coefficients of friction (mu) for the anchor head against the rock, including 0.15, 0.3, and 0.45. The results indicated that within the chosen range of anchorage depths, the extent of damage increases with the depth of anchor embedment. However, the depth of anchoring, considering the studied range of this parameter and the assumed mechanical properties of the rock, did not have a significant effect on the value of the angle cone (alpha(0)) during the initial phase of the medium's destruction. For the friction coefficient mu = 0.15, there is a clear deep penetration into the fracture at its initial stage of development (at the initial angle of alpha(0) = -20 degrees), promoting further spread of the fracture on the free surface. For larger values of the friction coefficient (mu = 0.3 and 0.45) - the trend is less pronounced (alpha(0) = -2 degrees divided by-8 degrees) resulting in a decrease in the crack range.