The shear strength of coarse-grained soil is a critical mechanical parameter. Traditionally, the shear strength of granular materials has been described using the Mohr-Coulomb criterion. However, this classical approach does not account for the influence of particle breakage, which can significantly affect the mechanical behavior of such materials. A combined theoretical and experimental approach was employed to investigate the shear behavior of coarse-grained soil under high vertical stress. It was observed that particle breakage occurs on the shear failure plane. Based on these findings, a power-law function was proposed to describe the shear strength of coarse-grained soil. Assuming that the particle shear surface conforms to the fractal distribution, and the shear strength is all derived from the friction between the particles, the fractal theory based on the shear strength of coarse-grained soil is derived. Then, the automatic high-pressure direct shear instrument was used to carry out high-pressure direct shear tests on three materials: calcareous sand, gypsum and hard diatomaceous earth. The effects of the initial porosity ratio and vertical stress on the shear characteristics were investigated, and the results showed that the initial porosity ratio did not affect the shear strength and vertical displacement, but with the increase of vertical stress, the shear strength and vertical displacement increased. The shear strength is related to the vertical stress by a power function. The debris collected after the test was sieved to obtain the fractal dimension. This value was then substituted into the fractal shear strength formula. The predicted shear strength showed good agreement with the test results, verifying the validity of the fractal shear strength theory for coarse-grained soils.
Xu Yuran
,
Zhang Jia
,
Xiao Hairong
,
Xu Yongfu
. Research on the Shear Crushing Strength of Coarse-Grained Soils Based on Fractal Model[J]. Chinese Journal of Underground Space and Engineering, 2025
, 21(S2)
: 659
-668
.
DOI: 10.20174/j.JUSE.2025.S2.15
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