Compensation grouting in Perth CBD and its numerical backanalysis

Gima V. Mathew and Barry M. Lehane

This paper reports on the ability of compensation grouting to reduce tunnelling induced settlements and investigates potential means of modelling such grouting numerically. The monitored movements of the ‘Walsh building’ during boring of two tunnels in Perth CBD (forming part of the MetroRail City Project) are used to show that compensation grouting (in sand) can greatly reduce movements. The 2D finite element (FE) back analyses indicated that the grouting can be modelled effectively in FE analysis by imposing a volumetric strain to the mass of soil subjected to grouting. Improved understanding of how grouting may be modelled numerically can increase the efficiency and cost-effectiveness of grouting.