Abstract
Acoustic emission has a direct correspondence to the internal damage of a material. To determine the effects of the loading rate on the mechanical properties of rock, the initial damage was characterized using the acoustic emission technique when a uniaxial preloading was imposed on a cylindrical rock sample. On this basis, the uniaxial compression test was conducted on sandstone that contains initial damage induced under a range of loading rates. The effects of the initial damage and loading rate on the mechanical properties of rock were analyzed. The uniaxial preloading generated randomly distributed microcracks in the natural rock. The results showed that the acoustic emission and positioning technique can characterize accurately the damage and its position due to preloading. The development of microcracks was found to be strongly dependent on the loading rate. Moreover, the loading rate accelerated the degradation of the rock strength. The effects of the loading rate and initial damage on the mechanical properties of rock are a complicated coupled process. From the experimental test result, a constitutive equation was constructed based on the damage mechanics.
Highlights
IntroductionThe number of high-strength mining faces in Western China has increased
In recent years, the number of high-strength mining faces in Western China has increased
High-speed advances bring significant economic benefits and have a negative impact. erefore, it is important to understand the influence of the initial damage and loading rate on the mechanical properties of rock to prevent a disaster during mining
Summary
The number of high-strength mining faces in Western China has increased. E probability of disaster induced by rock failure increases as the advancing speed increases in a working face [1]. To examine the relationship between the advancing speed of the working face and the rock stress transfer mechanism, basic experimental studies have been carried out in the laboratory due to many difficulties related to onsite research. 0.03 0.05 0.07 0.09 and Zhang et al [18] examined the effects of the shape and quantity of damage-induced fissures on the mechanical properties of brittle materials, of which regularly distributed initial fissures had been prefabricated artificially. Uniaxial preloading is imposed on a brittle rock sample to generate initial damage in the form of microcracks in this study. From the experimental test result, a constitutive equation was constructed based on the damage mechanics
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