A series of laboratory tests is performed to study the influence of drainage condition and coarse grain content on the dynamic residual deformation characteristics of the saturated gravel soil. Extensive tests are carried out under no-drainage

single-drainage and double-drainage conditions respectively

by using the improved GDS cyclic triaxial testing system. The gravel soil samples consist of five different gradations. The results indicate that

the dynamic residual shear strain is dominated by both the coarse grain content (the content of coarse particles

whose diameters are bigger than 5 mm) and the drainage condition. The residual shear strain significantly decreases as the coarse grain content and the number of drainage surfaces increase. When the number of the cyclic loading reaches 30

the dynamic residual shear strain under the no-drainage condition is 2-3 times that under the single-drainage condition

and 4-9 times that under the double-drainage condition. However

the dynamic residual volumetric strain of the saturated gravel soil decreases with the increase of the coarse grain content

as well as the number of drainage surfaces. The corresponding dynamic residual volumetric strain under the double-drainage condition is 2-2.5 times that under the single-drainage condition.