A 3-D finite element analysis of low-pressure grouting

A finite element approach is discussed for the analysis of low-pressure injections of diluted chemical Solutions in granular soil deposits. This technique represents, in fact, one of the possible provisions used in tunnelling practice to reduce the "natural" permeability of pervious soils and to limit the seepage flow towards underground openings excavated below the water table. The grouting process is modelled as the advective-diffusive-dispersive flow of a liquid containing a solute. First, the equations governing this process and their finite element formulation are discussed. Then, an empirical law is presented for the variation of permeability with time and with the concentration of the solution. Finally, the results of a series of three-dimensional analyses are discussed and, on their bases, some conclusions are drawn on the effectiveness of the treatment.