A graphical method for predicting ground movements from pipe jacking

The need for a relatively simple graphical technique for predicting the lik ely ground movements caused by pipe-jacking operations is established. The two analysis methods used to derive the graphs are briefly described. The f irst of these methods is based on the Gaussian distribution curve analysis and the second uses an analysis based on constant volume shearing (termed h erein 'modified Sagaseta analysis'). The derivation of the graphs used for predicting ground movements, based on these two methods, is then discussed. Two graphs are presented: one enables the immediate vertical surface and s ubsurface ground deformations to be predicted; the other enables the immedi ate horizontal surface and subsurface deformations to be predicted for a pl ane perpendicular to the direction of pipe-jacking operations. These two gr aphs, together with the application notes, allow the complete immediate two -dimensional ground displacement field associated with pipe-jacking operati ons to be determined. The graphs are applicable to tunnel diameters in the range 0.5-3.0 m and depths up to 15 m. Good quality field monitoring data a ssociated with pipe-jacking operations are quite limited. However, the accu racy of the graphical method presented in this paper is tested using the da ta from three instrumented pipe-jacking operations described in the literat ure. It is shown that the predictions made by the proposed graphical method are reasonable, although there are some anomalous results. It is envisaged that as more field monitoring data become available the graphical method c an be updated to incorporate new findings, thereby improving the accuracy o f the predictions obtained. The practical need for establishing the ground movements for pipe-jacking operations is shown in terms of the likely effec ts these movements have on adjacent existing services, such as cast-iron pi pelines.