Effect of fines content on strength of silty sands

An experimental study on sands with different content of nonplastic fines(particles smaller than 0.075 mm in diameter) was performed.It was shown that the strength and strain of the silty sands were affected by fines content.Silty sands with fines content of 6%,9% and 12% exhibited static liquefaction under the confining pressure of 100 kPa,but samples with fines content of 0%,3% and 15% did not.And the static liquefaction disappeared under the confining pressure of 200 kPa.For a kind of silty sands with certain fines content,the friction angle which was relevant to the residual stress difference was higher than that to the peak stress difference,but the residual stress difference was quite low,because the increase of pore water was fast,and counterbalanced the advantage of the increase from ?p′ to ?r′.The steady state line moved downward with the increase of fines content.The strength of samples with different fines content was more sensitive to the confining pressure than that of clean sand.The influence of fines content on void ratio was remarkable when the fines content was more than 12%.It was shown that the void between load-bearing grains was not entirely filled with fines of low content and might be only filled with the fines were on the contact of the sand grains.Silty sands with the sand-silt fabric were highly compressible and exhibited typical strain-soften characteristics and instability under low confining pressure.