Framework for optimisation of uplift pressure monitoring and maintenance of drainage holes

In this project, a number of drainage holes at the lamella dams at Storfinnforsens and Ramsele will be studied. A model will be developed to describe the efficiency of the drainage holes over time and how this can be used to predict future pore pressure and its impact on the stability of the dams.

To evaluate the safety of existing concrete dams, their stability needs to be analyzed. One of the largest loads acting on concrete dams is uplift pressure. Due to their low weight, lamella dams are particularly sensitive to uplift pressure. Therefore, it is common to drill drainage holes in the bedrock to lower the pore pressure and simultaneously monitor the pore pressure level.

A problem with drainage holes is that their efficiency reduces over time due to clogging. The knowledge of the mechanisms that control this clogging is poor, making it difficult to predict the future function of the holes and how they should be maintained.

In a previous stage of this project, spatial distribution of pore pressures in the bedrock was examined. It also investigated how alarm limits should be set. By combing this knowledge with the results of this project, a model of the entire system can be established. This comprehensive model can be used to optimize the monitoring of pore pressure and the maintenance of drainage holes, contributing to improved dam safety and ensuring that unnecessary stability-enhancing measures are not implemented on our existing concrete dams.