Experimental Evaluation of the Shear Behavior of Fiber-Reinforced Calcareous Sands

Abstract

Fiber-reinforced calcareous sands manifest unique properties of increased shear strength and particle breakage. These features are of practical importance for some offshore engineering constructions because the strength improvement and efficient dense compaction of soils are both important. This paper presents experimental evaluations of the characteristics of shear strength and particle breakage of fiber-reinforced calcareous sands by direct shear and ring shear (RS) tests with different vertical loading stress, fiber content, and fiber length. In the tests, the mixture of fiber and sands can make the specimen a spatially interlocked and unitary coherent network with efficient stress transmission. In addition, the overall deformation of the sand specimen would increase with the fiber content due to low stiffness of fiber elements. Thus, in direct shear tests, the secant elastic modulus decreased, while the shear strength increased with the fiber content. The contribution of fiber to the shear strength of the sand specimen came mainly from the friction and tension forces exerted when they were deformed. These two forces could mobilize the additional shear resistance of sands and thus increase the overall shear strength of the sample. In the RS tests, the breakage intensity of calcareous sands increased with the vertical loading stress, fiber content, and fiber length. At low fiber content and length, the interparticle contacts and interlocking effects influenced the shear strength and particle breakage significantly, while at higher fiber content, the role of fiber friction and tension forces became dominant.