Controlling grout spreading in tunnel grouting - Analyses and developments of the GIN-method

• In order to choose the best grouting technique, predictions of the grouting result can be made. Due to uncertainties in the predictions, control of the grouting during ongoing work is an important step towards a successful result. One method to control the grouting is the GIN-method developed and presented by Lombardi and Deere (1993). The method focuses on controlling the grout spreading in order to minimise the risk of hydraulic uplift and achieve a more uniform spreading around a bore hole. However, this method is described with emphasis on dam grouting. In this paper, theories are analysed and developed from a tunnel grouting point of view. A concept of a normalised pressure and normalised grout spreading is presented that at the same time enables control of the grout spreading distance as well as the risk of hydraulic uplift. Calculations based on field data are also done in order to visualise and discuss the potential use of developed theories. Some conclusions from the performed analyses are that other mathematical relations than those stipulated by the GIN-method better account for the risk of hydraulic uplift and that higher pressures than the rule of thumb stipulates could be used in good rock. So far, the concept of normalised pressure and normalised grout spreading is in its first stage and is studied mainly from a theoretical point of view. Further studies are thus needed.

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