Rhéologie des coulis d'injection

Directeur du Laboratoire de la Société Solétanche.

Résumé

A very wide range of reliable grouts are now available, from cement to synthetic high polymers, which differ by their chemical properties and setting process, but their use mainly depends on their rheological behaviour. There is a suitable grout for each type of ground, e.g. visco-rigid Bingham suspensions for coarse ground, colloidal non-rigid grout for medium sand and very low viscosity pure solutions for fine sand. The first part of the report deals with this classification, and the parameters to be considered in grouting operations are reviewed, i.e. discharge/pressure relationships, the effect of grout age, etc. Successful grouting depends on intimate knowledge of rheological graut properties. Where the grout is too coarse or the injection rate too high to allow complete impregnation, the grout progresses 'explosively', first vertically and then soon afterwards, horizontally. This effect is only of interest where it is desired to constitute an impervious bottom but is undesirable and should be avoided in all other cases, as it wastes grout and causes trouble at ground level. By varying the type of grout with decreasing ground permeability, this 'explosion' effect can be avoided. Factual examples are given at the end of the report. Initial use of highly Newtonian grouts should be avoided, however, as they are more costly and show poor strength properties in coarse ground when left to flow under gravity before setting.