New experience in ground treatment by permeation grouting

Abstract

In the last few years, ground treatment has made significant progress. Innovative products include environmentally friendly grout mixes based on colloidal silica, which are capable of permeating fine sand even with some silt content. Different mix designs were studied in depth and refined in laboratory trials, in order to define a range of products that could be used for the consolidation and reduction in permeability of soil and fissured rock. In the case of fine and soft soil conditions, low grouting pressure and flow rate need to be utilised, increasing the grouting schedule significantly. In order to carry out the work properly and efficiently, a new injection system was developed, allowing the simultaneous and selective grouting of specific layers. These new mixes and injection system were recently tested in a test programme performed in the very fine and soft soil of Rome, as part of the soil improvements for the construction of the new tunnels and stations for the expansion of the subway system (Roma Metro).