An Analytical Method of Predicting Length of Grout Penetration in Jointed Rocks

Prediction of the length of grout penetration and assessment of the groutability around the boreholes in the jointed rocks have a crucial effect on the planning and execution of grouting. Grout distribution in jointed rocks is a function of the geomechanical properties of rock mass, grout properties, and grout operational performance. This paper describes an analytical model based on the Newton’s second law, with the assumption of disk-shape model for the joints in order to calculate the maximum length of grout penetration in the horizontal and angled joints. It is shown that the proposed formulas can predict the length of grout penetration in rock masses with numerous joint sets as well. In order to validate the proposed model, it is compared with the existing analytical and empirical criteria, showing a very good accordance with their calculated results. Finally, the proposed analytical model is used to design the grout planning of a water conveying tunnel that is subjected to a heavy inflow. The design results in a successful filling of the vacant space behind the segmental lining and sealing the tunnel to stop the inrush water. These show that the model proposed in this paper can be successfully applied in practice.