Abstract:
Grouting of rock fractures is one of the main activities in tunnelling through fractured rock, and determination of an optimum grouting pressure is crucial for the success of the project. In this paper, an analytical approach was used to evaluate the performed grouting in a tunnelling project in Sweden. Optimized pressure is a function of the required spread distance of the grout mix while limiting dilation of rock fractures to a certain maximum amount. The proposed approach determines grouting pressure, in conjugation with in-situ rock stresses, to control the dilation of fracture during the grouting process until the grout mix spreads to the required distance, where the grouting is called completed. This analytical approach was used to evaluate both the design concept and the executed grouting work. First, possible dilation of the fractures due to the design pressures and the corresponding spread of grout were estimated. Later, the data from the executed grouting work were evaluated to assess the efficiency of the used pressure and consequences of rock fracture jacking. Finally, the optimized pressure and stop criteria for the studied cases are discussed. It is shown that this analytical approach is beneficial to control rock fracture jacking and spread of grout while improving penetrability and reducing grouting time. KEYWORDS Grouting and Pre-grouting, Tunnelling, Rock Fracture Jacking, Analytical Solution, Case Study