Finite-element analysis of a compensation grouting field trial in soft clay

This paper presents the details of, and results from, finite-element modelling of a monitored field trial of compensation grouting in Singapore Marine Clay. The numerical results are compared with the ground surface response and the pore water pressures that were monitored during the trial grouting programme. Notable features of the field trial were that: (a) the ground heave achieved during a one-day grouting cycle reduced during the subsequent three-day rest period before the next grouting cycle commenced; and (b) the excess pore water pressures generated during that one-day grouting cycle dissipated to almost zero during the three-day rest period. The Imperial College Finite Element Program was used to analyse this field trial. The method for the modelling of compensation grouting is described. Two alternative grout propagation models are compared, one of which produces a good match with the field recorded heave data, and the other with the field recorded pore pressure data. The hydraulic boundary conditions are also varied to look at the consolidation behaviour. It is concluded that the proposed finite-element model can reproduce field behaviour if excess pore pressures can dissipate to the injected grout itself. The analyses also suggest that the direction of grout propagation in the field probably varies as the grout is pressurised.