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Rock Pressure Grouting
(Fissure Grouting)

Rock Pressure Grouting has a long history of use in dam construction and rehabilitation, and can be applicable to challenges in mining, tunnelling, rock mechanics and environmental remediation. Rock grouting is typically performed to reduce the hydraulic conductivity of, or more appropriately, across a rock mass by injection of grout into the rock's joints and fissures.

The end product of the in situ treatment of a rock mass by grouting is commonly referred to as a grout curtain, which can be considered as a two-dimensional 'structure' across which a significant hydraulic gradient can be resisted. An extreme example of such a grout curtain is Geo-Foundations' work at the 55-metre deep outfall shaft at the Niagara Tunnel project, where, once the shaft was excavated, the negative side of the grout curtain was air at atmospheric pressure and the positive side was ground water under 55 metres of hydrostatic pressure.

Grout curtains are constructed by successive orders (primary, secondary, etc.) of drilling and grouting of multiple grout holes, each of which is drilled, cleaned, water-tested and grouted - usually with cement-based suspension grout - in sequence. With appropriate equipment, personnel and instrumentation, a sophisticated grouting program can be performed with verifiable results. Real time monitoring and recording of pressures and flows allows for the adjustment and optimization of grouting parameters in response to the evolving hydraulic signature of the rock mass. Analysis of this recorded body of work, coupled with an appropriate number of hydraulic conductivity tests, can unmistakably show the reduction in hydraulic conductivity (measured in Lugeons) achieved over time and from one stage of grouting to the next.

Geo-Foundations has a rich history of experience in rock grouting, including construction of several grout curtains below existing dams and proposed mine tailings ponds.

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