Spatial Variability of Subsoil Properties of Guwahati City Using GIS Based Maps

Spatial Variability of Subsoil Properties of Guwahati City Using GIS Based Maps

With major facilities such as sports complex, educational institutions , hospitals, flyovers, multiplex halls, etc., Guwahati, the main town in the North Eastern region of India, is growing rapidly in every aspect. In order to ensure the structural protection and serviceability of the above-mentioned structures before any building, awareness of the subsurface soil conditions is important. Therefore, using the Geographical Information System ( GIS) platform and contour maps of Standard penetration test N value, Liquefaction potential map and shear wave velocity map, the ground water table would be of great help to the foundation designers at the initial stage for site selection and preliminary foundation design in static and seismic conditions. Contour maps of the Standard N-value penetration test at different depths and the average N-value contour map of the city of Guwahati were prepared. Normal penetration Test N for penetration In order to prepare the N value contour map of Guwahati region, the values and depth of the water table were taken from a data base of 200 boreholes up to a depth of 30 metres. A regression equation based on twenty-seven previous similar correlations was also established between shear wave velocity Vs and Standard penetration test N value. For determining the shear wave velocity of Guwahati region, this regression equation was used. For all places, the average shear wave velocity of 30 m depth was calculated and used to generate maps on the (GIS) platform. In Guwahati region, seismic soil liquefaction was assessed in terms of the safety factor against liquefaction and the likelihood of liquefaction along the soil profiles and presented as maps showing zones of liquefaction risk levels. In order to form a database, other subsurface geotechnical details of Guwahati region, such as soil classification, depth to water level from ground surface, are also provided in the form of GIS based maps.

Author (s) Details

Binu Sharma
Department of Civil Engineering, Assam Engineering College, Assam, India.

S. K. Rahman
Department of Civil Engineering, Assam Engineering College, Assam, India.

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