A STUDY OF DYNAMIC SHEAR MODULUS AND BREAKAGE OF DECOMPOSED VOLCANIC SOILS

Small strain shear modulus, G_(max), is considered as a fundamental stiffness property for the soils and it is very important material parameter in design and analysis of geotechnical structures. It is also very important to estimate the particle breakage and its effects on mechanical properties required in engineering design. In this work, small strain shear modulus and breakage of five different volcanic soils were investigated in the reconstituted state. Reconstituted soil is common in the construction of geotechnical structures and their behaviour at very small strain is of utmost significance. This was achieved by conducting bender elements testing in triaxial stress path cells on uniformly graded volcanic soils. The particle breakage was estimated and analysed based on total energy input. The decomposed volcanic soils have weaker and crushable particles. The G_(max) increases with particle breakage which in turn increases with total energy input. A new model equation has been proposed for the estimation of G_(max) of volcanic soils. The small strain shear modulus is accurately predicted using empirical equation proposed for sand but the accuracy of prediction depends on the coarse fraction of the soil.