To study the effect of particle shape on shear modulus of sand

four sand samples with different particle shapes and grain sizes are prepared

including Fujian standard sand and artificial quartz sand. Image Pro Plus and Matlab program can extract the geometric parameters of particles from images of four samples obtained by scanning electron microscope. Two geometric parameters

radius angularity and form index

are improved and studied. Through statistical data of sand particle

the results show that radius angularity and form index describe different aspects of particle shape. As such

shape factor of sand is proposed based on radius angularity and form index to generalize particle shape. Then

a series of model tests in K0 condition is conducted to obtain the shear modulus of samples under different vertical stresses by bender element deployed in the sand. The tests show that shape factor is closely related with shear modulus of sand. Finally

based on Hertz-Mindlin contact model

shape factor is introduced to derive the formula of sand’s shear modulus

which agrees well with the measured one.