Rini Kusumawardani, FT Teknik Sipil (2023) A retrospective view on liquefaction-induced flowslide and lessons learned - an example of Petobo failure incident during 2018 Palu Donggala Indonesia earthquake. In: 9 th International Congress on Environmental Geotechnics, 25-28 June, 2023, Chania, Greece.

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Abstract

Soil liquefaction is an important issue in the field of environmental geotechnics where level ground loses its bearing, causing failure or settlement of structures. In cases of river bank or mildly sloping ground, however, liquefaction-induced lateral spreading or flowsliding would be more devastating, where struc�tures on the ground would be ripped or drifted away for distance. One of the striking events was the series of liquefaction-induced flowslides in Balaroa, Petobo, Jono Oge, and South Sibalaya, triggered by the 2018 Palu-Donggala Indonesia earthquake, resulting in ground movements of more than 1000m and causing significant damages and casualties. Post-failure investigations indicated the sliding areas were generally situated on a sloping ground of minor relief (<5% or <3°), with crests bordered a main irrigation waterway, Gumbasa canal. In addition, extensive wet-rice cultivation of the ground, in associ�ation with Gumbasa irrigation system, would appear to have had elevated the local groundwater tables. With these findings, the potential causes of the failures could therefore be envisaged. This paper will discuss the causes of the liquefaction-induced flowslide failures, with a particular interest on the Petobo sliding. Relevant evidences from our site reconnaissance and subsurface investigations will be adopted as supports to the causes of failure. We also conduct a series of engineering analysis and try to verify the potential effects of various influence factors on the consequence of the flowslide. In summary, this paper will address retrospectively the lessons that we could learn from the extensive and long-distance flowslides induced by soil liquefaction.

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