Subsurface ground movements due to circular shaft construction

Abstract

The rapid development of modern metropolises has led to a shortage of surface space and, in response, engineers have pursued alternatives below ground level. Shafts are commonly used to provide temporary access to the subsurface for tunnelling and, as permanent works, are utilised for lifts or ventilation purposes. The construction sequence of axisymmetric shafts makes them a dramatically simple solution. In addition, circular shafts are inherently stiffer than other plan geometries. Those are perhaps the reasons why circular shafts are preferred in situations of restricted space or unfavourable ground conditions. However, due to the lack of case histories reporting ground movements induced by shaft construction, no empirical prediction method for subsurface soil displacements exists. The work presented here seeks to provide clearer insights into surface and subsurface soil displacements induced by circular shaft construction by means of an analysis of measurements obtained from centrifuge tests and available field data. Novel empirical equations and procedures are then suggested for practical use.