By means of direct shear test of the riverbed sandy cobble and broken stone

the shearing strength parameters variation regular pattern are comparatively analyzed under different test conditions; and dry density or percent fines adjust sandy cobble and broken stone shearing strength. The results of test indicated that the shearing strength parameters are increased if dry density are improved for the two kinds of coarse grained soil; the fricton angles are stable amount in little percent fines

the shearing strength parameters are reduced when percent fines are increased. The interlocking force are tended to stable amount when dry density are much improved in different test conditions for different coarse grained soil. The test results indicated that the shearing strength parameters of the unsaturated consolidation direct shear test are larger than the saturated consolidation and riverbed sandy cobble shearing strength are larger than broken stone’s too. The shearing strength parameters are increased if dry density are improved and finally to steady tendency for the same riverbed sandy cobble。