Prof. D. N. Singh

ANJAN PATEL

Ph. D.
Indian Institute of Technology Bombay, Powai, India anjanP_14@yahoo.com

APPLICATION OF PIEZOCERAMIC ELEMENTS FOR SOIL MASS CHARACTERIZATION

Shear and compression wave velocities (Vs and Vp, respectively) have been demonstrated to be quite useful for determining basic engineering properties of the soil mass by earlier researchers. To achieve this, resonant column, cyclic triaxial and tortional shear tests have been employed. However, these methods are not only quite elaborate and expensive but require skilled manpower, are cumbersome and time consuming. This calls for development of an alternate methodology that can be employed for characterizing the soil mass, which is not very intricate and is cost-effective. In this situation, usage of piezoceramic elements (i.e., bender and extender elements, which can be employed for measuring Vs and Vp, respectively) seems to be a good option. With this in view, an attempt has been made in this study to develop a simple and cost-effective methodology for measuring Vs and Vp in different types of soils, compacted to different compaction states. This methodology incorporates in it the optimal performance of different bender and extender pairs. The suitability of the methodology has been demonstrated for characterization of the soil mass for engineering purpose. Using this methodology, Vs and Vp were measured in the laboratory for different types of soils in their dry and wet conditions corresponding to different various compaction states. Based on the results, empirical relationships have been developed between Vs and soil specific properties (viz., void ratio, effective stress, and size, shape, roundness and sphericity of the particles). However, for cohesive soils, Vs has also been correlated to the compression index, undrained shear strength and various index properties (viz., plasticity, fine content and moisture content) of the soil mass. Attempts have also been made to develop generalized relationships that can be used for determining basic geotechnical engineering properties of the soil mass, quite easily, just by inputting Vs. Also, a comparison has been made between the Poisson's ratio and elastic modulus of the soil mass obtained from Vs and Vp measurements, and conventional triaxial tests.