Effects of jet grouting on adjacent ground through numerical modelling

Abstract

When using jet grouting for soil stabilization, effects of the installation process, such as erosion or remolding of the surrounding soil, need to be evaluated. This could be particularly important for applications in challenging ground conditions and low initial ground stability. This study investigates such effects in soft marine clays (undrained shear strength of 20-30 kPa) using numerical finite element simulations for both flat and sloping terrains. Additionally, an analytical solution using the modified Hagen-Poiseuille equation was developed to i) assess the pressure induced by the grout at any installed depth, and ii) illustrate the importance of maintaining a proper amount of return flow to avoid build-up of excessive pressures in the ground during the jet grouting process. Combining the analytical and the finite element (FE) simulations, jet grouting induced soil displacements were determined. For flat terrain, the area affected by jet grouting was approximately three to four times the column radius. By contrast, for the studied slope (inclination of 1:3), the influenced area increased to about 10 times the column radius. The influenced area could increase further for steeper slopes. The obtained displacement magnitude was also considerably larger for sloping terrain than for flat terrain. The reported findings relate to jet-grouting in marine clays (which is not the normal application of this technology) and cannot be extrapolated to other soils.