Characterization of rock in 2D and 3D for grouting

Paper i proceeding, 2012

© BeFo and ISRM, 2012. In tunnel construction in hard rock, a common method to reduce water inflow is to perform pre-grouting. The grouting design should be adapted to the current rock mass conditions, as well as to the stated inflow requirement for the tunnel project. One step in the grouting design process is to make a prediction of the expected inflow into the tunnel. The objectives of the research reported in this paper were to increase the understanding of fractures in 3D for grouting, to improve an existing method of inflow prediction so that hydrogeological aspects such as 3D fracture systems can be captured, and to increase the understanding of how grouting design should be adapted to the fracture system. It was concluded that a relevant conceptual model of the rock mass is good basis for grouting design and for inflow prediction. Conceptual models which describe different types of fracture systems are presented: 2D systems, 3D systems, fracture zones, flow dominated by 1D, and combinations of 2D-1D flow. Awareness of anisotropy is important: identification of the most water-bearing fracture set is essential both for inflow prediction and for grouting design. To illustrate the findings, data from case study tunnels have been analyzed.