Potential areas susceptible to Liquefaction in National Capital Region, India

Liquefaction is a phenomenon triggered by the vibrations of earthquake tremors in saturated loose soil. It is a major seismic risk particularly for the urban areas with large number of buildings and infra-structures, which are likely to be collapsed or toppled down due to destruction of foundation by this phenomenon. An attempt has been madehere to identify the potential areas susceptible to liquefaction in the National Capital Region of Delhi(NCR). Geological set up shows that a large part of the NCR is covered with Older and Newer Alluvium, and seismically the NCR falls under High Seismic Zone – IV. Further, Yamuna River flows through the NCR that shows water table at shallow level at most of the places particularly along the river channel. All these are favourable for the possibility of liquefaction in the region. It is, thus, important to delineate the areas that are susceptible to liquefaction so that risk due to liquefaction may be reduced, especially where high rise buildings and mega infra-structure are already existing and even coming up in different places of the NCR. Accordingly, field and laboratory data fromvarious parts of NCRwas collected to study the geotechnical parameters of the sub-surface strata and water table, which are the conditioning factors for the occurrence of liquefaction.Data from 182 boreholeswas collected and generated covering a large part of the NCR up to the depth of 30 m. Field test, viz. Standard Penetration Test (SPT) was conducted, and soil samples collected from each borehole were tested in the laboratory to understand the physical, strength and deformation (behavior) properties leading to assess the bearing capacity. Liquefaction analysis was carried out on the soil atdifferent depths in all the 182 boreholes using the method as given by Seed et al. (1983, 1985), leading to delineate the potential areas where soil is susceptibility to liquefaction. These areas as suggested by the analysis include a large partof East Delhi, area along Noida-Greater Noida Expressway, and some part of Rohtak, Jhajjar and Sonipat.