The application of strength grouts to the rehabilitation of existing concrete gravity dams

A new way of improving the stability of concrete dams on rock foundations was investigated involving the development of cohesion in the unbonded contacts of the dam foundation interface by specifically designed strength grouts, using Type 10 Portland cement and MC 900 cement. It was shown that cement based grouts, having low bleed at small viscosities, develop tensile strengths within concrete-rock contacts that exceed 0.4 MPa. This paper presents a methodology to assess the suitability of increasing the stability of a concrete gravity dam through the injection of these specifically-designed strength grouts into the dam-foundation interface. It was shown that strength grouting can be carried out using current grouting practices that are familiar to contractors and engineers. Similarly, it was demonstrated that adequate increases in the safety factor can be obtained even if field grouting achieves only a relatively low penetration ratio in the unbonded interface. 6 refs., 1 tab., 6 figs