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This present study was to investigate the potential geotechnical causes of the failures of two earth-filled embankments occurred in 2017 in Thailand. The Huai Sai Kamin embankment dam was the first failure that occurred on July 28th. The Nong Sano reservoir was the second failure that occurred on October 18th. Geological, geotechnical and hydrological data were collected and analyzed together meteorological data. In addition, site visits were performed to collect soil samples for testing. The results show that the embankment of the Huai Sai Kamin dam was well compacted of clayey sand (SC) over an alluvial soil and two tributaries, Huai Sai tributary and Huai Nam Bo tributary. Water overtopping during the tropical depression, Sonca caused the Huai Sai Kamin embankment to breach. The breach occurred at two sites. One site was at the remnant of Huai Nam Bo tributary and the other site was at the irrigation conduit. An inadequate spillway capacity and inadequate maintenance were the causes of such water overtopping. The embankment of the Nong Sano reservoir was compacted of sandy lead clay (CL) over the sandstone, siltstone and mudstone of the Khorat Group. The Nong Sano embankment was breached due to the embankment that contained a significant amount of dispersive clay. Rehabilitation of the Nong Sano reservoir should consider the problem of the soil type used for constructing an embankment, while the rehabilitation of the Huai Sai Kamin dam should consider a spillway capacity and a proper maintenance.
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