Effects of initial suction and degree of saturation on dynamic properties of sand at large strain

Abstract

4Soil deposits may experience different hydraulic states in terms of suction (ψ) and degree of 5 saturation (S r ) while subjected to large strain caused by dynamic loading during earthquakes. 6 This phenomenon is investigated by considering the effects of initial ψ, initial S r , sample 7 preparation method, drainage condition, and cycle number (N) on dynamic properties. Shear 8 modulus (G) and damping ratio (D) are specifically studied for an unsaturated sand using a 9 modified cyclic simple shear device for all zones of soil water retention curve (SWRC). 10Results revealed the relative significance of both ψ and S r in relation to SWRC on observed 11 trends in G and D. Through analyzing some results from the literature, it was shown that most 12 of the data follow a sigmoid function in the plane of normalized stiffness (G/G sat ) versus 13 suction normalized to the air entry value. It was also revealed that minimum damping is not 14 in conjugation with maximum stiffness due to the contribution of other mechanisms in 15 damping like inter-particle water lubrication. Comparison between results of two testing 16 methods indicated a notable influence of initial fabric on G. Furthermore, the overall trends in 17 G and D against N are marginally influenced by initial ψ and S r .

Very-small to large strain dynamic behaviour of unsaturated sand in a wide range of suction

“…It can be seen that the G 150 /G max increases with an increase in suction, yet when reaching the residual zone of the SWRC, the normalised value decreases approximately exponentially until reaching 50 kPa of suction. It seems that the reduction of G 150 /G max after 3.7 kPa of suction may be because at residual zone, the water phase in the soil became discontinuous and this may hence lead to a reduction of the contribution of capillary suction [21][22][23].…”

An evaluation of the effect of matric suction on the dynamic strain-dependent parameters of an unsaturated silt

“…The medium to large strain tests on unsaturated soils have also revealed the degradation of the unsaturated shear modulus and the aggradation of the damping ratio with strain level in all unsaturated tested specimens. In addition, it is shown by previous researches that an increase in matric suction would result in an increase in the shear stiffness and a decrease in the damping ratio [17][18][19][20][21][22][23].…”