Abstract
Seismic hazard assessment often relies on static piezocone penetration tests (CPTu) to estimate the cyclic resistance ratio (CRR) and for the evaluation of in situ soil behavior. This article presents CPTu data acquired in the Kathmandu valley sediments and makes use of established CPTu interpretation procedures to assess the soil in situ properties. Up to this point predominantly SPT data and limited shear wave velocity measurements have been relied upon to assess the variability and seismic response of soil deposits underlying Kathmandu. This article provides 1) additional data to add to the existing SAFER/GEO-591 database, 2) new shear-wave velocity measurements, and 3) initial estimates of CRR at the sites visited. Based on the work presented in this article, it is concluded that a more detailed methodology is needed for liquefaction assessment mainly due to the presence of saturated silts in the valley.
Highlights
Nepal has many rural populations as well as urbanized areas with building stock whose frequency and distribution of structural typologies remain uncertain
This article has presented some new geotechnical field observations for the Kathmandu valley which have helped build a better understanding of the possible geotechnical impacts from earthquakes
The soils are saturated and are of a mixed composition which are typically difficult to classify and assess for liquefaction potential. These conditions, where there are excess pore water pressures (Δu) may mean that the soils have the potential to liquefy and, even within the well-established cone penetration test (CPT) and liquefaction frameworks are difficult to characterize. This makes the Kathmandu valley an important place for future testing of these existing CPT interpretation procedures and expansion of future work into understanding the specific parameters needed for the soils in Kathmandu
Summary
Nepal has many rural populations as well as urbanized areas with building stock whose frequency and distribution of structural typologies remain uncertain. The impact of earthquake hazard is likely to increase as urbanization of the world’s cities increases (United Nations, 2018). Areas where urbanization is dominated by building stock constituting mainly non-engineered local construction are subject to even higher vulnerability due to earthquakes (e.g., Giordano et al, 2021). Nepal is an example of such an area. A lack of high-quality information to aid the development of retrofitting or reconstruction efforts is a barrier to the improvement of seismic resilience. The earthquake hazard assessment relies on the availability of high-quality ground data. The availability of high-quality geotechnical testing data and geophysical equipment for the measurement of Vs is driving uncertainty in the assessment of site response
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