Abstract
The deterioration of rock geomechanical behaviors subjected to freeze–thaw (F–T) action is a determining factor for rock engineering and rock structures in cold regions. In this work, taking six groups of granite obtained from an open pit mine as the research object, F–T cycle treatment, in-situ AE (acoustic emission) monitoring and ultrasonic detection techniques were performed to experimentally reveal the effects of F–T fatigue damage on the mechanical and acoustic properties of granite. The results indicate that the F–T action impacts the rock’s mesoscopic structure, deformation, strength, P and S-wave velocities, AE pattern and energy release. The accumulated AE counts and accumulated AE energy show a decreasing trend as the F–T cycle increases. The frequency spectrum revealed that the width of the low frequency band decreases and the high frequency band increases with increasing F–T cycles, indicating that there is an increase in large-scale cracks for a sample with high F–T treatment. In addition, energy balance analysis further illustrates the energy dissipation and release mechanism. The energy proportion used to drive the crack propagation is relatively small with high F–T treatment, and the final released energy becomes the minimum. The energy evolution characteristics analyzed by the energy balance approach is in good agreement with AE results. It is suggested that the F–T fatigue damage influences the rock energy storage and release characteristics and the instability of rock in the cold regions.
Highlights
In recent years, with the depletion of open-pit mining resources in the low-altitude plain areas, the exploitation and utilization of metal mineral resources in cold regions at high altitude has become the national priority of China
For the granite samplesTest subjected to F–T treatment, uniaxial compression testing was conducted on a GCTSFor rock mechanics
The results indicate that even though the rock is very compacted, the moisture can still penetrate into rock defects, such as native micro-cracks and mineral boundaries
Summary
With the depletion of open-pit mining resources in the low-altitude plain areas, the exploitation and utilization of metal mineral resources in cold regions at high altitude has become the national priority of China. Cyclic freeze–thaw (F–T) actions result in the deterioration of rock’s physical and mechanical behaviors, and the associated stability of an open mine pit slope. The damage deterioration characteristics of various kinds of rock, such as granite [5], dolomitic limestone [14], diorite [15], tuff [16], sandstone [17], oil shale [18], coal [19] and slate [20] from different cold regions in. The damage and mechanical behavior of rock subjected to F–T treatment have both been widely investigated; the current studies on F–T rock mainly focus on the macroscopic stress–strain responses, where mapping of the internal strain filed is typically only observed after failure; for example, with macroscopic crack pattern descriptions. The fracture evolution characteristics and acoustic emission characteristics of rock during the whole deformation have been studied in detail
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