Effect of Bench Size on the Strength and Deformation Properties of Interphase Between Benched Bedrock and Soil-Rock Mixtures

For the high-fill slope with soil-rock mixtures (SRMs), the bedrock under the SRMs can be excavated into many benches to improve the mechanical properties of bedrock-SRMs interphase and the stability of the slope. However, this improvement effect by bench size is still unclear. The continuous-discrete coupled method is a powerful tool for analyzing the interaction between soil and structure, soil and rock, etc. Firstly, this paper proposes a fine discrete element modeling method for rock blocks and develops a continuous-discrete coupled method for the benched bedrock-SRMs interphase. Then, a series of numerical direct shear tests for the benched bedrock-SRMs interphases with different bench sizes are conducted. The effect of bench size on the shear mechanical properties of the interphase is systematically investigated in terms of rock block rotation, contact force chain distribution, crack distribution, shear stress-displacement curve, and shear strength. The numerical results demonstrate that the bench size has a considerable impact on the strength and deformation properties of interphase. Raising the height or height-width ratio of the benched bedrock can enhance the interaction and skeletons between the benched bedrock and SRMs, thereby improving the strength and deformation properties of the interphase. Compared to increasing the bench height, increasing the height-width ratio has a more significant effect. Finally, a shear strength prediction method for the benched bedrock-SRMs interphase is proposed based on the Mohr-Coulomb strength criterion, which is practical in the design and stability evaluation of high-fill slope with SRMs.