SHEAR MODULUS RELATIONSHIPS FOR GRAVELLY SANDS

sandy soils, there is only limited data on gravelly soils. This paper presents an experimental study on shear modulus characteristics of gravelly sands. It is found that soil modulus coefficient (K 2max) ranges from 86 to 92 for gravel and from 50 to 63 for pure sand. Sand with 20% gravel has lower maximum shear modulus (Gmax) whereas Gmax increases with further increase in gravel content (GC). The study emphasizes that cyclic shear strain amplitude (γ cy) and number of cycles (N) are the two main parameters needed to characterize cyclic response. The effect of γ cy is pervasive in determining the value of the initial shear modulus (G) at the onset of cyclic loading and the rate of stiffness degradation with cycling. Stiffness degradation increases as γ cyincreases beyond 0.05%. The rate of stiffiiess degradation becomes slower with increasing relative density (Dr), effective confining pressure (σ^/ c), and GC beyond 20%. Gravelly sand deposit has a constant characteristic modulus reduction curve G/Gmax versus γ cy irrespective of Dr and σ^/ c. Modulus reduction curve for 20% gravel almost coincides with the sand curve, however, the curve shifts downward as GC further increases. Comparisons of these results with published data are discussed.