An Approach to Estimate the Atterberg Limits of Pilani Soil Using Ultrasonics

The present study aims to develop calibration curves to estimate liquid as well as plastic limit by
knowing ultrasonic pulse velocity through it for Pilani soil. The Atterberg limits are basic measure of
the critical water contents of a fine-grained soil. They are its shrinkage limit, plastic limit, and liquid
limit. Depending on water content, four physical states of soil consistency are used. The water
contents at which soil undergoes physical state change are called Atterberg limits. Liquid as well as
plastic limit are two commonly used Atterberg limits and are used extensively, either individually or
together, with other soil properties to correlate with engineering behavior such as compressibility,
compactibility, shrink-swell and shear strength. Conventional method of liquid limit determination
requires test to be conducted at 5 (at least) different water contents for accurate estimation. Even
liquid limit estimation using cone penetrometer requires more than one trial. Similar trials are involved
in plastic limit estimation. Sand content has effect on its liquid and plastic limit, as well as ultrasonic
pulse velocity through it. Consequently, it should be possible to estimate liquid and plastic limit by
knowing ultrasonic pulse velocity through it. Ultrasonic pulse velocity using through transmission
technique (at constant water content and density); as well as their liquid and plastic limits using
conventional techniques at varying sand content were determined and plotted for Pilani soil. This plot
can be used as calibration curve for aforementioned estimation purposes and can be developed for
other region soils as well. Similar calibration curves can be developed for other reigon soil also, and
hence developed calibration curves in present study involving the determination of ultrasonic pulse
velocity through soil is of great significance.