The Prediction of Ground Movements Adjacent to Box Excavations
Summary
Thames Water’s Crossrail Project team required a simple method of predicting ground movements around complex shaped station excavations as a verification tool for the Crossrail 3D FEA based damage assessments.
Existing commercial software did not take into account the corner stiffening effects of box excavations where the deflection of the wall will be greatly reduced.
The London Underground (LU) technical advice note for the prediction of movements around short wall’ excavations provided a method of predicting ground movements around the Crossrail stations. However, the use of the Advice Note was time consuming and extrapolation of the data provided gave rise to irregular displacement profiles. Horizontal movements can only be predicted perpendicular to the box excavation wall.
Development of the LU methodology was undertaken and incorporated into an Excel based software package. Innovative use of the LU horizontal movement predictions also allowed x and y vectors of movement to be developed along the asset.
This output of the digital LU based method for the prediction of ground movements compared very closely with the 3D FEA generated predictions and was a valuable tool in the agreement of the final mitigation strategy for Thames Water assets.