Evaluation of Static Liquefaction Characteristics of Saturated Loose Sand Through the Mean Grain Size and Extreme Grain Sizes

Liquefaction of soils is a natural phenomenon associated with a dramatic loss of the soil shear strength in undrained conditions due to a development of excess pore water pressure. It usually causes extensive damages to buildings and infrastructures during earthquakes. Thus, it is important to evaluate extent of influential parameters on the liquefaction phenomenon of soils in order to clearly understand the different mechanisms leading to its triggering. The soil gradation is one of the most important parameters affecting the liquefaction phenomenon. In this context, a series of undrained compression triaxial tests were carried out on eighteen natural loose (Dr = 25%) sandy samples containing low plastic fines content of 2% (I_p = 5%) considering different extreme sizes (1.6 mm ≤ D_max ≤ 4 mm and 0.001 mm ≤ D_min ≤ 0.63 mm) and two mean grain size ranges (0.25 mm ≤ D₅₀ ≤ 1.0 mm) and (1.0 mm ≤ D₅₀ ≤ 2.5 mm). The initial confining pressure for all tests was kept constant (P′_c = 100 kPa). The obtained test results indicate that the mean grain size (D₅₀) and extreme grain sizes (D_max and D_min) have a significant influence on the undrained shear strength (known as liquefaction resistance) and appear as pertinent factors for the prediction of the undrained shear strength for the soil gradation under study. The undrained shear strength and the excess pore water pressure can be correlated to the extreme grain sizes (D_max and D_min) and the mean grain size (D₅₀) of tested wet deposited samples.