A Study on Characteristics of Soil Profile of Guwahati City Against Different Ground Motions: 1D NonLinear Ground Response Analysis

Abstract

One-dimensional nonlinear (NL) ground response analysis (GRA) is carried out for four locations viz. Dharapur and Azara area, VIP and Rani area, Jalukbari area and Assam Engineering College (AEC) area of Guwahati city. The analysis is done with the help of 23 boreholes using Indo-Burma earthquake, 1997 recorded at Nongpoh station and Indo-Burma earthquake, 1988 recorded at Nongstoin station with duration 52.94 s. These two input motions are further scaled up to 0.18 and 0.36 g and used for the GRA analysis. The response of the substrata obtained after the analysis has been presented in terms of peak spectral acceleration, maximum shear stress profile, strain distribution and peak ground acceleration (PGA) for all the locations irrespective of every motions. For most of the locations, soil layers with high SPT N value, generally stiffer soil, resulted in a lower value of surface PGA compared to soft soil layers. The PGA and overall energy content of the strong motion significantly affect the response of a multilayered soil profile, keeping all other parameters constant. Higher strain amplitudes have been observed at various sites and at various depths of the soil profiles which may undergo settlement or earthquake-induced liquefaction. The peak spectral acceleration obtained is much higher for 0.36 g scaled motion compared with the spectral acceleration of rocky or hard soil sites (IS: 1893–2002) for both the earthquakes which indicate sensitiveness of the locations to the induced motions.