Bearing Capacity Factor Nq Estimation of Pilani Soil Using Ultrasonics

Abstract

As per IS: 6403-1981, bearing capacity factors Nc, Nq and N are required in order to get the net ultimate bearing capacity. They depend strictly on the soil's angle of shearing resistance. Soil’s cohesion is also required in order to calculate net ultimate bearing capacity. Cohesion and angle of shearing resistance of soil is determined using drained direct shear testing, unconfined compression testing (undrained) or undrained triaxial testing depending on soil condition at site, all of which require complicated experimental setup. Lengthy calculations are also involved. As an alternative to it, ultrasonics has been used in the present study to obtain estimated value of Nq for Pilani region soil. Knowing ultrasonic P wave velocity, estimated value of cohesion, angle of shearing resistance and Nq can be obtained from the calibration curve developed in the present study. Other bearing capacity factors are then obtained using equations available in the literature. Consequently, net ultimate bearing capacity can also be conveniently determined. Ultrasonic P wave velocity determination through soil requires very simple experimental setup. Developed calibration curve thus has lot of advantages. Similar calibration curves can be developed for other regions soils also simplifying the process of bearing capacity factors and net ultimate bearing capacity determination.