A L Moxhay, principal author and ground improvement consultant, R D Tinsley, Surface Wave Surveys, J D Redgers, Soletanche Bachy France and D C Gravell, software development consultant. This paper was first published in GE’s September 2008 issue.
The continuous surface wave (CSW) technique (Matthews et al., 1996, Menzies and Matthews, 1996) relies on the propagation properties of vertically polarised seismic surface waves, or Rayleigh waves. It measures seismic shear wave velocity and hence minimum-strain stiffness (Gmax) as a function of depth. The method has been used to monitor the effectiveness of ground improvement on construction sites for the past ten years.
Surface wave testing is nonintrusive and therefore better able than invasive methods to cope with the huge variation in grain size which occurs in overburden throughout the UK (Moxhay et al., 2001).