Seismic Imaging of Unstable Ground

Abstract

Unstable ground conditions caused by unexpected collapse of existing buried infrastructure or incidents during tunnelling represent major geotechnical risks. Specially developed crosshole, SUBS and SEWREEL seismic imaging technologies that operate from boreholes and underground openings can be applied to define the subsurface extent of the unstable ground and to monitor the effectiveness of remedial works. These technologies use below ground hydrophone arrays and surface seismic sources. A case study of a shallow sewer collapse that followed a rainfall event in a beach suburb of Sydney, demonstrates the application of these imaging technologies, showing their ability to define the resulting unstable ground hazard and to assist with geotechnical risk reduction.