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Investigating the effect of layering on the formation of sand boils in 1 g shaking table tests
Published in Andrew McNamara, Sam Divall, Richard Goodey, Neil Taylor, Sarah Stallebrass, Jignasha Panchal, Physical Modelling in Geotechnics, 2018
S. Miles, J. Still, M. Stringer
Sand boils form in the field as a result of the upwards flow of pore water, which occurs as a result of the high excess pore pressures that can exist following strong ground shaking (i.e. Towhata 2008). If the upwards flowing fluid reaches the ground surface with sufficient velocity, then material from the liquefied soil layer can be transported to the ground surface, where it is rapidly deposited as the flow velocity decreases.
Reconnaissance Report on Geotechnical Engineering Aspect of the 2015 Gorkha, Nepal, Earthquake
Published in Journal of Earthquake Engineering, 2019
The liquefaction potential of soils in the Kathmandu Valley was conducted by UNDP/MOHPP [1994], JICA [2002], and Piya [2004]. Past research concluded that a large area in the Kathmandu Valley is susceptible to liquefaction (Fig. 14). Liquefaction susceptibility was rated “high” to “medium” in areas along the major rivers and channels. However, liquefaction cases triggered by the present earthquake appeared to be fairly limited and localized. The areas where liquefaction was observed are Manamaiju, Ramkota, Bungmati, Jharuwarasi, Hattiwan, Imadol, Mulpani, and Duwakot (Fig. 14). Sand boils were formed by freshly ejected sand forced out of overpressurized ground surface. At most sites, sand was ejected to agricultural fields forming deposits that varied from thin veneers to sheets of a few centimeters thickness. Liquefaction-induced damage to structures in these areas was not found except that buildings in some places tilted slightly. Incipient liquefaction was also observed at many places including Gongabu, Kaushaltar, and Lokanthali. Soils at those locations except Jharuwarasi are considered to have the moderate to high liquefaction susceptibility according to UNDP/MOHPP [1994] and Piya [2004].
Erosion time scale in pipes below dikes for turbulent and laminar flow
Published in Journal of Hydraulic Research, 2023
As a result of differences between the water level in front of and behind these water defences, pressure differences occur, which force water to flow underneath them. Downstream of these structures, first, a well is created, i.e. a location where seepage water rises from the subsoil. If the pressure difference exceeds a critical value, then pipes grow from the downstream to the upstream sides. During high water periods, this process results in sand boils, due to sand being carried out of the aquifer by seepage.