Nouveau coulis à base de ciment pour le scellement d'ancrages dans le roc gelé du Grand Nord

Abstract

At present time, in frozen rock, the anchors are not grouted with conventional cement grouts as these are inefficient, or deteriorate with the formation of ice lenses during the freezing of the mixing water. The problem is avoided by boring deeper into the rock mass, until the unfrozen horizon is reached, if accessible, or by using thermal protection systems, which result in additional costs. Substantial economies may be obtained by grouting the anchor in the frozen rock, along a length necessary and sufficient to insure the stability of the structure, by using an antifreeze grout with a Portland cement base without resorting to thermal protection. In this context, the results of a study carried out in the Far North are presented, including pull-out tests of anchors grouted with a Portland cement base grout in a rock frozen at −12 °C. The resistance to frost of the cement grout has been achieved by using an antifreeze chemical admixture, the sodium nitrate (NaN02), which has allowed the setting of the anchors without heating the steel bars, the rock, or the grout. The results obtained show that the cement grout used may be considered as an efficient grouting product for the design of grouted anchors in the frozen rock or in the permafrost of the Canadian Far North. Key words: frozen rock mass, permafrost, grouted anchor, pull-out test, Portland cement grout, antifreeze chemical admixture, Canadian Far North, Arctic.