a method to detect hydraulic jacking during anisotropic rock mass grouting

The hydraulic jacking phenomenon refers to the process of crack growth of the pre-existing joints in the rock mass under grout pressure above the minimum in situ stress. therefore, in the grout operations, it is essential to understand the resistance behavior of rock-joints to avoid the hydraulic jacking. this paper describes a novel method for determining the hydraulic jacking occurrence based on the principle of fracture mechanics. hence, the jacking mechanism has been assessed in three stages: 1) developing an equation to calculate the stress intensity factor (sif) of joints in the anisotropic media; 2) determining the fracture toughness by employing brazilian disc test (bdt); 3) assessing the stability of joints using the maximum tangential stress (mts) criterion. by comparing the joint stress intensity factor and fracture toughness, the joint stability was evaluated. to validate the proposed method, the results of boreholes used to construct water curtain at sanandaj azad dam in phyllite rocks were analyzed. finally, it is concluded that the growth and expansion of joints due to the instability under grout pressure led to the increased cement take and the occurrence of hydraulic jacking.