This article summarizes the geotechnical effects of the 25 April 2015 M 7.8 Gorkha, Nepal, earthquake and aftershocks, as documented by a reconnaissance team that undertook a broad engineering and scientific assessment of the damage and collected perishable data for future analysis. Brief descriptions are provided of ground shaking, surface fault rupture, landsliding, soil failure, and infrastructure performance.
Hydropower infrastructure, the primary source of electricity in Nepal, experienced severe damage following the 2015 Gorkha earthquake sequence, resulting in a 15% loss in the country's energy production. The performance of hydropower infrastructure during and after the sequence was one of the unique focuses of the Geotechnical Extreme Events Reconnaissance (GEER) study. The GEER team visited damaged hydropower projects along the Trishuli and Sunkoshi rivers by road and on foot, along with the ongoing 465-MW Upper Tamakoshi hydropower project by helicopter. The primary cause of damage to the hydropower infrastructure was landslide and rockfall debris falling on powerhouses, penstocks, and dam structures. Moreover, landslides blocked road access to many sites, delaying necessary repairs to damaged structures and resumption of power generation. Power production in Nepal before and after the 2015 Gorkha earthquake sequence, seismic performance of visited hydropower projects, and short- and long-term effects, together with residual risks for Nepal's hydro-power infrastructure, are discussed in this paper.
It was recognized that repeated stages and substages of glaciation in Saskatchewan during the Pleistocene Epoch produced a series of overlapping sediments. It was shown that these sediments could be analyzed for engineering purposes within a three-dimensional stratigraphic framework. Preliminary field investigations indicated that a stratigraphic analysis could be related to construction problems found on highway embankment construction, gravel location, and tunnel excavation. Field studies established that it is practical for the field engineer to analyze and interpret the stratigraphy in the field. Furthermore, laboratory studies indicated that there were significant differences in the engineering properties of different drift-stratigraphic units. It was shown that the behavior of the till units during construction could be explained in terms of the fundamental engineering properties of soils such as shear strength parameters and compressibility. Finally, it appeared to be probable that the basic concepts developed in this study would apply to other areas covered by glacial sediments.
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