Modelling and acoustic monitoring of grout propagation in sands

Abstract

Grouting is generally used for ground reinforcement or for reducing soil permeability. However, choosing grouting parameters or predicting improvements is at present rather empirical. A numerical approach may therefore enable grouting to be more efficient. The purpose of this paper is to model the evolution, in time and space, of two major variables: grout concentration and fluid pressure in grouted soil. After a brief description of a first tried diffusive model, this study aims to describe the performance of a software program, Athos. This program was initially developed for the oil industry and uses a piston model. Results are given in one- and three-dimensional approaches. They underline a rapid evolution of concentration from groutsaturated zones to non-saturated zones. The evolution of pressure depending on this degree of saturation is also highlighted. The second part of the paper compares the numerical model with a series of experiments carried out on grouted sand columns and in saturated sand tanks. In the latter tests, the grout is injected into the sand using a sleeved grout pipe, and the progress of grout propagation in the soil is monitored by acoustic emission (AE). This comparison shows the validity of the chosen model. The permeation distance detected by AE is compared with that predicted by simple grout propagation models.