Experimental study on the dynamic mechanical characteristics of slope rock under low-temperature conditions

Abstract

China has large regions that freeze seasonally or multiple times a year. Special geological and climatic conditions must be considered for the engineering construction and mining of mineral resources in these regions, and slope stability in cold regions merits study. Taking the Yulong Copper Mine in the Tibet Autonomous Region as an example, the average altitude of this mining area is approximately 4000 m, the average daily minimum temperature in the coldest month is approximately −20 ℃, and the freezing period is long. Slope stability is considerably affected by freezing and thawing, and frozen rock creates several challenges to blasting and excavation, thereby restricting mine production efficiency. To study the dynamic mechanical characteristics of slope rock under low-temperature conditions, marble samples are drilled from the slope of the Yulong Copper Mine. With the help of the SHPB experimental system with a low-temperature control system, dynamic compression and tensile mechanics experiments are performed on rock samples under normal temperature and dry conditions, normal temperature and adequate water conditions, and low-temperature freezing conditions to explore the influence of temperature and water content on rock dynamic mechanical properties. The experimental results show that (1) the average uniaxial dynamic compression and tensile strength of frozen rock samples at −20 ℃ are increased compared with those at room temperature under the joint influence of water/ice phase transformation at low temperature and rock matrix cold shrinkage. Among these phenomena, the latter is the main reason that the strength of frozen rock increases substantially. Under four strain rates, the compressive stress increased by 1.30, 1.62, 1.41, and 1.43 times, and the tensile stress increased by 1.36, 1.28, 1.22, and 1.29 times, respectively. (2) Under the influence of pore water softening, a saturated rock sample has less dynamic strength than a dry rock sample. Therefore, the experimental data under the same strain rate show that the strength of a rock sample follows the order of frozen > dry > saturated. (3) For a given strain rate, the dynamic impact crushing time of saturated marble is the longest, and the decrease with increasing strain rate is the fastest. For a given strain rate, the crushing energy consumption is larger for a rock sample at freezing temperature than at normal temperature and increases greatly with increasing strain rate.

Keywords

• cold region slope
• frozen rock
• shpb
• dynamic characteristic
• broken characteristics