Pavlick Harutoonian

Investigation of Composite Compacted Ground Using Microtremors

AbstractThis paper presents an interesting and unique case study of a composite compacted site where the upper section of dynamically compacted material achieved in the first stage of compaction was subsequently removed, reinstated, and recompacted in lifts in the second stage using conventional roller compaction. Dynamic compaction was employed initially in this area because of the need to densify deep fill materials. Although a number of mechanical methods are already available for assessing deep compaction, it has been particularly rare to find a cost-effective method that can be applied to a deep and extensive compacted site. Noninvasive techniques based on measurement of the horizontal-to-vertical spectral ratio (HVSR) of ambient vibrations (microtremors) are proposed in this paper to assist in a pilot appraisal of this area, which occupies a part of a deep and laterally extensive compacted site. First, the key features of the measured HVSR curves were interpreted to give a preliminary insight into t...

Characterisation of an urban site by ambient noise HVSR Method : resonance frequencies and site amplifications

The resonance frequencies and site amplifications of a proposed development site on the Penrith campus of the University of Western Sydney have been studied by means of a non-invasive ambient noise Horizontal to Vertical Spectral Ratio (HVSR) method. Unlike other non-invasive surface wave techniques (such as the SASW, MASW, CSW etc) which require an array of connected sensors, the HVSR technique is a single station method requiring no such connection. Moreover, the HVSR technique is a passive method in relying only on the ambient microtremors caused by natural events (tides, large-scale meteorological conditions) and cultural activities (industrial machinery, cars and trains) as excitation sources. This paper presents one part of a study which aims to characterise the site effects and layered soil stratigraphy of a development site at the Penrith campus. In this study, measurements of the ground responses in the vertical and two orthogonal horizontal directions were carried out using a lightweight battery operated, wireless 3-component digital tomograph. The estimated HVSR curves, the resonance frequencies and site amplifications, and interpretations of the results obtained for the site are discussed. The experience from this study indicates that this could be a low-cost and attractive technique having a great potential in near surface geotechnical characterisation of urban sites. Further investigation is currently being undertaken to study its efficiency and accuracy in establishing the S-wave velocity profiles and soil stratigraphy of the site by inverse analysis of the HVSR curves.

Near Surface Soil Characterisation by Passive Ambient Noise HVSR Method

This paper discusses the use of the passive horizontal-to-vertical spectral ratio (HVSR) ambient noise method for near surface characterisation of the soil layers at a proposed building site. The uniqueness of the HVSR method is in having no need for any external excitation sources and cabling, and the setting up time is also very short. In our study, HVSR measurements were taken at spots interspersing the few available bore logs, with each measurement taking no more than 10 minutes. This allows the entire site to be measured very expeditiously. The HVSR spectra were then inverted by fitting measured to theoretical spectra values to obtain the V s profile of the underlying soil layers, based on an assumed layered soil model. A side benefit of this approach is that the resonance frequencies of the site were also determined without undertaking additional work. In addition to benchmarking the soil profile inverted from the HVSR measurements against the available bore log data to verify its accuracy and correctness, comparisons have also been made with the results from the MASW and ReMi array- based methods. The study shows that the HVSR method performed very well against these surface wave methods. It is thought that the HVSR technique would be especially cost-effective for characterising a large site in conjunction with a few bore logs.