Geotechnical and Geophysical Investigations with Pga Estimation of the Kathmandu Fun Park Project, Thankot, Kathmandu, Nepal
Date
2014
Authors
Journal Title
Journal ISSN
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Publisher
Department of Geology
Abstract
This work focuses on the study of the foundation characteristics by geotechnical and
geophysical investigations with PGA estimation of the Kathmandu Fun Park Project (KFPP)
located in Thankot area, Kathmandu.
To obtain information on subsurface material, velocity distribution and soil thickness seismic
refraction survey was conducted using a 24 channel seismograph system by Oyo. Other soil
properties were studied by in-situ Direct Cone Penetration Test (DCPT) and laboratory test of
samples. The problem of ground shaking in the case of large earthquake near the Kathmandu
valley is assessed in terms of synthetic peak ground acceleration (PGA) due to the lack of
observed data. The present study provides tools for estimating geotechnical parameters from
seismic wave velocity in the area where soil test are difficult to conduct. Fewer amounts of
observed data and unavailability of instruments for undisturbed sampling have somehow
affected this research work. Manual picking of travel time data from waveforms has affected
the subsequent processing and interpretation of seismic refraction data.
The study area comprises of colluvium deposits, mainly washout with high clay content. The
high moisture content, low unconfined compressive strength and low bearing capacity of the
soil are noteworthy. A modeled equation relating the P-wave velocity and porosity for the
Lesser Himalayan colluvium soil has been established together with the material velocity.
Similarly, the PGA distribution due to 1934 Taplejung, 1988 Udayapur and other two
hypothetical earthquakes shows the PGA may exceed 150 gal for earthquakes greater than
magnitude 8. However, the result shows the PGA hardly reach 15 gal for small but strong
earthquakes. Moreover, the geotechnical parameters, specially moisture content, unconfined
compressive strength, friction angle and porosity, show reasonably good correlation with
seismic P-wave velocity. The single field measurement (i.e. seismic P-wave velocity) can
serve the best for estimating other geotechnical parameters.
Description
Keywords
Geophysical investigations, Seismic refraction, Peak round acceleration, Fun-park