Numerical Modelling of Displacement Grouting – Application to Excavations

This paper deals with numerical modelling of displacement grouting. Firstly, the main phenomena associated with compensation grouting are presented. In the case of compaction grouting, the heave mechanism is studied to explain the strain transmission mode. The compaction grouting efficiency is also analysed in the case of excavations. The compensation injection technique is increasingly used in urban areas to mitigate soil movements, particularly to correct settlements induced by excavations or tunnels. This method requires a fine monitoring instrumentation to track in real time the effects of the injection in the soil, as the estimation methods for soil movements caused by injections are still not fully validated. The article initially presents various physical phenomena inherent in the injection of a grout in soil. Subsequently, focusing only on compaction injections, a synthesis of analytical and numerical calculation methods is provided. A numerical procedure is proposed and compared to one of the analytical methods presented. The ground heaving mechanism initiated by deep cavity expansion is then investigated, and the characteristics of this mechanism are identified based on a study of the influence of the dilatancy angle. The potential for correcting settlements behind a supporting wall using this technique is then analysed.