Abstract: In view of the problems of local tension， cracking and collapse of the base material in the process of slope protection， the shear strength characteristics of the base material for 7 h， 1 d， 3 d， 7 d， 14 d and 28 d were investigated by using straw fiber as the base material modifier and considering two factors of cement and straw fiber. The experimental results showed that the increase of cement content and the prolongation of curing age increased the shear stress of the base material without straw fiber， the addition of straw fiber improved the ductility of the base material and delayed the shear failure process of the base material， and the increase of straw content effectively improved the shear stress and cohesion of the base material with different proportions， but had less impact on internal friction angle. The shear stress and cohesion of base material with 11% of cement and 4% of straw content for 7 h was increased by 54.68% and 136% separately， comparing with that of 0% straw； that for 3 d were increased by 42.15% and 206% respectively. The straw fiber had not a linear increasing effect on the shear strength of vegetation concrete base material， but weakened with the prolongation of curing age and the increase of cement content. The shear stress of base material with 4% straw and 11% cement for 28 day was decreased by 18.83%， and its cohesion was decreased by 32.87%， comparing with that of 0% straw， and yet its shear stress is higher by 11.84% and the cohesion is lower by 15.73% than that for 14 d. Thus， its weakening degree is closely related to the cement content and the curing environment.

Key words: Base materials for slope protection, Vegetation concrete, Straw fiber, Shear strength