Microtremor measurements of rolling compacted ground

Ground improvement works are commonly required to overcome poor underlying soils in conjunction with infrastructure and housing development. An extensively employed and popular improvement technique is to impart mechanical compaction to the ground in an effort to achieve adequate strength and favourable load-deformation behaviour (stiffness) for the construction of civil infrastructure, including buildings and roads. This paper describes the study of a passive ambient vibration (often also known as microtremors) HVSR based method for assessing compacted ground. Two methods to control this compaction process at a very large site were employed: (a) strictly controlled rolling compaction (b) visually monitored (by naked eye) rolling compaction. The key features of the measured HVSR curves have been studied and analysed to infer useful insights about the compaction achieved by the two methods. Furthermore, the fitting of these measured HVSR curves by trial-and-error forward modelling forms the basis for inferring the shear wave velocity (Vs) profile and layer thicknesses of the compacted ground. It is shown in this paper that the process of analysing and interpreting the HVSR curves, as well as the forward modelling of the HVSR curves reveal useful information about the quality and consistency of the compacted ground.