As a comment to what was presented before I would like to concentrate on two topics: - Goal of Theory - Practice
It is required to enlighten grouting techniques more than is presently the case because there are many questions open in answering what is going on in the ground under grouting procedures and in which way will the effort and the money spent be effective. It can be expected that theoretical considerations will be helpful. Necessarily, such considerations have to start with simplified models of the rock which has to be grouted. One point is that the rock conditions do not change during the grouting process. That means: No cracking should occur, since cracking would change the system of joints being grouted. Another point is, the grout mix should not change its properties during the procedure. That means: Hardening and hydration should not or almost not change the flow properties. In the case that solids are used which are suspended in water, no or almost no sedimentation should occur. Under such simplified conditions I would expect that theoretical considerations will help to find a better understanding of grouting procedures. Such considerations must not necessarily be followed by radical changes in grouting procedures which are now applied, according to the state of the art. Better understanding may help designers in their work to design, for instance, a grout curtain in the foundation of a dam. Better understanding will also help the engineers on site to adjust the procedures of grouting more effectfully and more quickly to the actual requirements. Last not least, better understanding will give more confidence to the Owners that their money is spent effectfully.
Designers of grout curtains are very often faced to the fact that the take of grout and subsequent effect can hardly be derived from the water pressure tests which are seen as to represent the permeability and the groutability of the given rock mass. There are many reasons for that: The differences in rheological properties of water and suspensions, the width of fissures which must fit to the coarse particles in the suspension, different pressures, and others. The consequence is: In parallel to water pressure tests grout tests should be made in individual boreholes during the investigation phase of a project. Competent Contractors which do correct core drilling and water pressure tests are commonly also competent in grouting. They will have available the respective equipment and skilled staff. It is a matter of the Engineer to convince Owners that such tests are fruitful and the money worth to be spent at the early phase. Such grouting tests will help the engineers involved to find a better feeling of rock groutability and of the grouting requirements in the given case. It is well known that in many cases the effect of grouting work is over-estimated, and much money is spent without an appropriate effect, namely to limit seepage to an acceptable amount.