Abstract
In the process of development and construction of open-pit mine slope in the high altitude and cold area, freeze-thaw (F-T) cycles have an important impact on rock engineering structure. F-T cycles lead to the decrease in physical and mechanical properties of rock, which is closely related to the stability of open-pit slope. In this paper, the influence of F-T cycles on geomechanical and acoustic emission (AE) characteristics of tuff specimens under different stress paths was studied by using F-T cycle treatment, in situ AE monitoring, and uniaxial loading test. The results indicated that under the same stress path, the cumulative AE count/energy of rock samples subjected to F-T cycles was less than that of rock samples not subjected to F-T cycles. The peak frequency distribution of AE signal during the loading process of rock specimen presented the phenomenon of frequency bands. The width of the low-frequency band of the rock samples subjected to F-T cycles was larger than that of the rock samples under the natural state. The frequency and width of the high-frequency band of the rock samples subjected to F-T cycles were larger than those of the rock samples under the natural state. The rock samples subjected to F-T cycles had higher plastic strain than those without F-T cycles. According to the uniaxial compression test results of F-T rock samples under different stress paths, the peak stress and peak strain have little change, but the AE characteristics were obviously different.
Highlights
In recent years, with the depletion of mineral resources in low altitude areas, the development and utilization of metal mineral resources in high altitude and cold areas have become the focus of China
Han et al [14] studied the damage mechanism of sandstone samples under the coupling effect of different chemical solutions and fast F-T cycles, and the results showed that the fracture toughness and strength of sandstone samples deteriorated to varying degrees with the increase in F-T cycles
The F-T fatigue damage of rock was analyzed from mass loss rate (M), F-T coefficient (Kfm), and P-wave velocity loss rate (P). e mass loss rate of rock sample was the ratio of the difference between the mass of specimen before and after F-T and the mass of dried specimen before the test; the F-T coefficient was the ratio of uniaxial compressive strength of rock after F-T to saturated uniaxial compressive strength of rock; the loss rate of P-wave velocity was the ratio of the difference of Testing group I
Summary
With the depletion of mineral resources in low altitude areas, the development and utilization of metal mineral resources in high altitude and cold areas have become the focus of China. In the process of mine development and construction, especially in the freezing and thawing environment, environmental geological disasters occur frequently. When water turns into ice in a cold environment, 9% volume expansion will increase the pressure in pores and microcracks [1, 2]. Frost heaving pressure drives the microcracks to propagate and produce new microcracks. E original microcracks widen with the deepening of microcracks, forming various rock mesostructures and corresponding mechanical properties. Freeze-thaw cycles lead to the decrease in physical and mechanical properties of rock, which is closely related to the stability of open-pit slope [3]. In order to ensure the safety and stability of mine slope engineering after F-T cycles, it is of great practical and theoretical significance to study the damage and deterioration characteristics of rock under F-T cycles
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