Study of Maliya Marine Clay for a Highway Embankment

Abstract

This paper presents study of the soft to very soft marine clay deposit, very thick and having challenging geotechnical engineering properties for a road embankment over it. These include a very low shear strength, high compressibility, low permeability, sensitivity, etc. It is the Maliya marine clay deposit in tidal swamp at Little Rann of Kachchh, an extremely flat coastal alluvium plain. This clay deposit is of 6.5 km width and up to 15 m thickness. Its engineering properties are determined through the elaborate laboratory testing program comprising of consolidated undrained CU circular direct shear box tests, vane shear tests, consolidation tests, and unconfined compression tests—all these tests on the undisturbed samples obtained at every 1.5 m from the bore-hole by the author up to 12 m depth. The field investigation consists of undisturbed sampling. The results of all these tests are presented in this paper for shear strength, strength versus strain characteristics, sensitivity, compressibility, and consolidation characteristics cv. The soil is mostly of CH group. Field moisture content exceeds liquid limit [60–70%]. Liquidity Index is compared. The values of the ratio of undrained shear strength to effective overburden pressure SU/p versus plasticity index Ip are determined and discussed. The top portion of this deposit, up to 2.4 m depth, is relatively stiff. Using ϕ = 0 analysis, stability analysis of a typical road embankment having 12 m top width and 7.5 m height and with berms and vertical sand drains is done incorporating the strength at 3% strain for the compacted embankment.