Vane Shear Test Apparatus: A Reliable Tool for the Soft Soil Exploration

There are deposits of fine clays on coastal areas in India. Those soils are soft, highly saturated, of low density, and low shear strength, sensitive, and normally consolidated. Such soils are generally termed as marine clays. Reliable undisturbed sampling of desired size in marine clays is generally difficult, and laboratory tests for determination of shear strength are also difficult for designing foundations of earth fills. In contrast, the vane shear test is a simple as well as reliable method in the hands of research workers.

Five sites for reclamation of dykes and road embankments around Bombay (India) were tackled. The height of the dykes and embankments varied from 2.5 to 7.97 m, and the depths of the marine clay deposits varied from 6 to 16 m.

During the foundation soil exploration, undisturbed soil samples were collected in open tube samplers from drilled holes. The vane shear test with its slow gear arrangement was carried out in the adjacent boreholes. The vane shear tests with vane borer (vane guard) were also conducted at one of the five sites.

Designing of the embankments, by the sliding block analysis method, was based on the average undrained shear strength determined during the vane shear tests. The settlement performance of the above embankments was studied and found to be satisfactory.