Geotechnical analysis of a retaining wall in weak rock

The determination of realistic values of stiffness and in-situ horizontal stress is challenging in softer materials, but in weak rocks where discontinuities are typically present it is particularly difficult. Such difficulties were encountered during the site investigation for the construction of the A444 Coventry North–South road retaining structures, where the in-situ lateral stress and stiffness profiles of the weathered sandstones and mudstone were determined using a range of investigation techniques. A section of retaining wall incorporating a stabilising base was monitored during construction, and further investigation of the weak rock was undertaken using geophysical techniques. Aspects of the observed performance of the retaining wall during construction were analysed using a continuum finite-element method to provide a computed stiffness and initial horizontal stress profile. The results from these analyses are compared with the site characterisation data.