Shear Strength-Dilation Characteristics of Silty and Clayey Sands

Abstract

Sandy soils usually contain different amounts of fines like silt and clay, causing some changes to their shear strength and dilation characteristics. Bolton [1] conducted some experiments on the different sands and suggested a relation between the parameters of the soil shear strength. In this paper, some experiments were performed on fine contained sand and the extended Boltonchr('39')s relation was has been proposed. In this paper, shear strength and dilation behavior of a pure sand mixed with different amounts of silt or clay fines were studied using direct shear test device (100*100*30 mm), and a total of 96 tests were carried out. The samples were prepared separately using clay and silt contents of 0, 10, 20 and 30% in different relative densities of 70, 80, 90 and 100%. They were tested under three surcharge pressures of 90, 120 and 150 kPa, under particle crushing threshold. Variations in shear strength, maximum friction angle, critical state friction angle and cohesion, as well as dilation angle were investigated by increasing in the mentioned amounts. The results demonstrate that shear strength, dilation angle, maximum friction angle decreased by clay content increase, however, they increase with increase in silt content. In addition, a new form of the Boltonchr('39')s relation for fine contained sandy soils was presented.