Risk Analysis Of BRPL Compressor (Offsites) Foundations


At the site of three instrument air compressors of Bongaigaon Refinery (BRPL) the top 6m of the soil had poor SPT-N values and 2-3% mica content. It was to be replaced with fine sand corresponding to the Grading Zone III sands of I.S. 383–1970 having D50 as 0.3mm to 0.4mm and no fines. However, the excavated pit had only been partly filled back with sand when monsoon waters inundated the pit and the work was stopped until the end of rainy season resulting in poor quality of fill. (Prakash and Kumar 1934, Kumar et al 1985). Liquefaction analysis of the soils by Seed's (1983) method showed that the soil within a depth of 4m to 9m would liquefy in an earthquake of magnitude 5.7 producing peak ground acceleration of 0.20g at the site. A probabilistic analysis had therefore been carried out to ascertain the risk involved due to liquefaction in the foundation soil. It was concluded that 1) there is high probability of liquefaction of soil, 2) large settlements and tilts may occur in the foundation blocks due to liquefaction under the 7.5 magnitude earthquake. © 1987, Elsevier Inc.


Civil, Architectural and Environmental Engineering

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Publication Date

01 Jan 1987