Inversion of meso parameters and triaxial test simulation of the gravel materials for high rockfill dam

Abstract: High rockfill dams with heights of over 100 m have been rapidly constructed in China at present. The self-weight of rockfill materials can cause the creep deformation of the dam body, and the uneven settlement on the panel of the high rockfill dam. It is necessary to evaluate the microscopic performance of dam materials during this time. Taking the High RockFill Dam Project in Artash, Xinjiang, China as the object, an orthogonal experiment was designed to determine the sensitivity of the mesoscopic parameters of gravel materials. Shear triaxial tests were performed on the large-scale consolidated drainage. A triaxial simulation was also carried out on the specimens with the different particle shapes, rock content and gradation using the Discrete Element Method (DEM). As such, the mechanical properties, deformation, and failure behavior of gravel materials were obtained from the macroscopic and mesoscopic perspectives. The simulation results show that: 1) There were prominent peak stress of block specimen and the more stable post-peak change, indicating the insignificant degree of shear expansion in the more stable structure. There was a small strength of the spherical specimen. The shear band formed after failure at a low rock content was a meandering strip with an asymmetric X-shaped distribution, where the shear failure surface reached 275.00 mm under the high rock content rate (65%) in the entire specimen, indicating easy to produce the multiple random failure surfaces. The force was more uniform and dense in the contact force chain distribution. However, the maximum force chain strength of the spherical specimen was reduced by 14.70 kN, compared with the rock specimen. 2) Under the low rock content state, the spherical specimens appear hardened and deformation which is mainly sheared, and the deformation has no outstanding peak. There was a significant peak in the deformation of the rock specimen under the high rock content rate, where the deformation behaved the softening and prominent shear expansion. The shear band changed from an asymmetrical "X" type to a "工" shape. The contact force chain showed a tendency from the small and dense to the uniform, and then the large and thin. The point numbers of bonding failure and destruction were greatly reduced from 10 000 (with a rock content rate of 0) to 6 800 (with a rock content rate 65%) The rock content of gravel materials had improved the strength and resistance to deformation. 3) There was a small degree of shear reduction and expansion of well-graded specimens. The shear expansion deformation of discontinuous graded specimens was prone to the shear expansion deformation and peak prominence. The discontinuous cascade mostly presented the surface of "工" or "X" type shear failure, whose width changed from 29.88 to 66.18 mm with the increase of particle size. There was a uniform distribution of force chain, but a small bearing capacity. The bonding failure point was displayed in advance, whose number sharply increased from 8 500 to 13 600, together with the high porosity of the particles, indicating the stress concentration was significantly prone to the failure mode. In conclusion, the material proportion with high irregular shape, high stone content and good gradation should be ensured as far as possible when selecting dam materials within the allowable range of conditions. Therefore, the graded continuous specimen presented better resistance to the deformation. The finding can also provide theoretical support for the stability evaluation of the Artash Water Conservancy Hub Project in western China.