Real-time analysis during pre-excavation rock mass grouting -methods and benefits

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During pre-excavation grouting (PEG) a considerable amount of data is continuously generated, but just a small part of this data is used actively during the PEG operation. A high potential remains in the unused data regarding optimization of the grouting operation. Today most of the grouting procedures are designed before excavation start-up and with little flexibility to adapt to the site conditions during the grouting itself. The Logic Grouting project, has collected data from several Norwegian projects and developed methods for real-time interpretation, suited as decision basis during PEG. The main attributes of these methods are notification of unexpected flow and pressure behaviour that has a high likelihood to be hydraulic jacking of fractures in the rock mass, and warning for holes with risk of high grout consumption. Both these indicators should lead to adjustments in the grouting procedure or grout mix, to ensure a successful grouting without excessive use of grout and time. Graphic display of flow and pressure during grouting has been available for many years but is seldom actively used by the operators, as it has no practical impact on their work. Optimization of the digital interface for the operators also need to be improved to fully utilize the potential of real-time interpretation during PEG. This paper presents the basis for the developed methods, statistics from Norwegian tunnelling projects and practical examples from on-site real-time analysis at the Sollihøgda tunnel in Norway.

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