Integration of invasive and non-invasive techniques in ground characterisation

This paper presents a case study, where non-invasive Horizontal-to-Vertical Spectral Ratio (HVSR) of microtremors was used to assess the compaction of a large site located in Western Sydney area in NSW. The integration of measurements of non-invasive microtremors, with invasive CPT and PS-logging techniques were investigated aiming to optimise the characterisation of the compacted ground. The invasive CPT and PS-logging tests were carried out sparsely at the compacted site due to the cost and they would only give spot-wise soil information at the test location. Hence there were many areas at the compacted site, where the quality of the compaction cannot be ascertained based on the invasive techniques. On the other hand, the low cost non-invasive HVSR technique is well suited for areal-wise site characterization in terms of the shear wave velocity, although not with the same reliability, detail and accuracy as the invasive methods. Integrating the two forms of techniques can thus help to exploit the respective strengths of invasive and non-invasive methods and optimize site characterization in terms of resources, cost and reliability. The study presented in this paper measured vertical and horizontal components of microtremors at regularly spaced stations across the site. The measured HVSR curves were then interpreted to obtain the shear wave velocity profile of the ground. Results show that the non-invasive HVSR technique can be successfully integrated with invasive techniques such as CPT and PS-logging to characterise large compacted areas