Shahzada KHURRAM, Perveiz KHALİD, Zia UD DİN

Geophysical Probing in Geotechnical Investigation for Shear Wave Velocity Assessment

In near surface geology attenuation and shear wave velocity are main factors in field of earthquake engineering to determine the characteristics of soil and subsurface material. Before construction geotechnical and geophysical tools were used to find the characteristics of subsurface. In this study, a single bore was drilled up to 50 m depth at site for material assessment and water table measurement. Silty clayey and clayey silt material was found at several depths. Downhole seismic survey was conducted on this single bore whole having dia 12 inches. On the basis of this geophysical tool, four layers were marked. The shear wave velocity increases with depth at 7 m is 250 m/s and compression wave are 430 m/s due to increase depth compressional wave increases up to 1750 m/s and having same rate at 50 m depth of borehole. This means under subsurface water is main carriers of the P wave at constant velocity. Whereas shear wave velocity regularly increases from 250 m/sec to 550 m/sec at 50 m. The rapidly increase of shear waves velocity indicates better compacted soil at depth which is good for foundation designing as well as earthing system.

Keywords:

P and S wave velocity, Attenuation Elastic modulus, Earthquake, Liquefaction potential,

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