Effect mechanism of block convexity on the shear behaviors of soil-rock mixtures by the developed 3D spherical harmonics-based modeling approach

The effect of block convexity on the shear behaviors of soil-rock mixtures (S-RMs) can be investigated using accurate 3D models constructed with the discrete element method (DEM). Based on the improved spherical harmonics series, a new block geometry modeling approach was proposed for generating 3D blocks with different convexities but the same form and angularity. By introducing tracer particles, a DEM modeling approach was also proposed for generating S-RM models with the same block distribution characteristics and possible block breakage. Numerical direct shear tests were performed on the generated stiff and soft S-RM models with different block convexities. The meso-and the macro-shear behaviors of the S-RMs were analyzed in detail to reveal the effect mechanism of block convexity. The results showed that the breakage degree of soft blocks increased lin-early with the block convexity degree. The interlocking degrees of blocks with higher convexities are higher, leading to higher contributions of the blocks to the shear strength and greater block rotation. As the effect of block breakage is more significant, soft blocks with higher convexity degrees contribute smaller to the shear resistance. For S-RMs with higher block convexity degrees, the shear strength of stiff S-RMs is higher owing to their higher block interlocking degrees, while the shear strength of soft S-RMs under high normal stress is smaller due to their higher block breakage degrees. The dilation magnitude is greater for stiff S-RMs while lower for soft S-RMs with higher convexity degrees, owing to the greater effect of block breakage than the rotation behavior. The friction angles of stiff S-RMs with higher block convexity degrees are larger due to their higher block interlocking degrees, while the friction angles of soft S-RMs with lower block convexity degrees are smaller under high normal stress due to their higher block breakage degrees.

Automated summary

The effect of block convexity on the shear behaviors of soil-rock mixtures (S-RMs) was investigated using accurate 3D models constructed with the discrete element method (DEM). A new block geometry modeling approach was proposed for generating 3D blocks with different convexities but the same form and angularity. A DEM modeling approach was also proposed for generating S-RM models with the same block distribution characteristics and possible block breakage. The shear behaviors of the S-RMs were analyzed to reveal the effect mechanism of block convexity.