Mechanical behaviour of natural silts for geotechnical earthquake engineering practice

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Liquefaction of soil has caused severe damage to buildings and lifelines during past earthquakes, and in turn, has led to loss of life and disruptions to living and working conditions of citizens. The Greater Vancouver Region of British Columbia (BC), Canada, is located in a zone of high seismicity, and it has been estimated that damage costs from a major earthquake in Vancouver could be over $30B with much of it associated with soil liquefaction. Much of the research focus so far has been on the liquefaction of sands since liquefaction has been observed predominantly in loose saturated sands. Recent earthquake experience suggests that liquefaction of natural silts is also a concern; it is also known that densification of silt to mitigate liquefaction is more expensive than the methods required for sands. Currently, there is no robust method to assess the liquefaction potential of natural silts primarily due to the lack of knowledge on silt behaviour. Hence, it is required to advance the fundamental knowledge on the mechanics of natural silts under seismic shaking; databases on silt response developed through systematic laboratory research are critical in this regard. Using Discovery Grant funds over the past six years, the applicant's research has led to initial findings on the silt behaviour and input for development of design guidelines. In the next five years, comprehensive experimental work on this subject involving four main research themes is proposed using the state-of-the-art facilities at the University of BC. The objective is to investigate the effects of the dominant physical factors on the liquefaction mechanisms of silts and develop engineering practice methods to assess liquefaction potential of silts using in situ testing. Three MASc and four PhD students will be trained during this work, thus adding to the earthquake geotechnical engineering expertise in Canada. The research findings will bridge the knowledge gaps on the behaviour of natural silts, and develop novel design methods with particular applicability to seismic design in civil and mining engineering fields.