Back Analysis of Crown Hole Development Using Numerical Techniques

This paper represents the back analysis of crown holes which developed on a section of the East Coast Main Line East of Edinburgh. A site investigation identified abandoned coal mines beneath the site, the collapse of which were causing the development of the surface instability. A single crown hole identified by the site investigation was chosen for this study. A representative model of the stratigraphy from borehole records was constructed using a finite difference program. The model was used to carry out a back analysis of the collapse of a single void with the aim of establishing the mechanism of collapse, the size of the underground voids and the reason for the delay of the collapse.