In this study, the liquefaction behavior of clean sand specimens is investigated in the framework of cyclic simple shear tests (CSSTs). The energy-based method (EBM) is the basis for presenting the results in this paper. The strain energy approach has been used to investigate the effects of changing the size of sand particles on its liquefaction resistance. The CSSTs have been performed under stress-controlled conditions on river sand at medium relative density (Dr = 52 %). The effects of changing the size of sand particles in CSSTs samples have been studied with the help of the mean particle diameter parameter D50 in six different grain sizes. Until now, the effects of varying sand particle size, especially for samples with D50 greater than 0.5 mm, on the cyclic liquefaction behavior of clean sands have been less systematically studied as a research gap using the elemental testing approach. The results of this study show that in a condition of the same relative density for sandy specimens with different particle sizes, an increase in the mean size of the particles along with changing the effective vertical stress on the samples causes a drastic decrease in the dissipated energy until the moment of liquefaction trigger of the specimens. For every 1137.30 % (11.37 times) increase in D50 values (i.e., from 0.252 mm to 3.118 mm), an 88.89 % decrease (i.e., from 4.50 to 0.50 kJ/m3) occurs in the accumulative dissipated energy.
