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| Loading rate effect and energy dissipation mechanism of dihydrate gypsum under confining pressures |
| LI Dong1，REN Gaofeng1，2，KE Bo1，2，ZHANG Congrui1，2#br# |
| (1. School of Resources and Environmental Engineering，Wuhan University of Technology，Wuhan，Hubei 430070，China；2. Key Laboratory of Mineral Resources Processing and Environment of Hubei Province，Wuhan University of Technology，Wuhan，Hubei 430070，China) |
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Abstract Implementing an experimental research on the evolution of gypsum mechanical characteristics at different loading rates has great theoretical research significance for the study of instability and failure of goaf as well as refinement treatment in gypsum mines. At a confining pressure of 10 MPa，triaxial compression tests of gypsum at different loading rates are implemented to study the effects of the loading rate on the physical and mechanical characteristics of dihydrate gypsum as well as energy accumulation，and to deeply analyze the law of energy evolution. The results show that the failure mode of gypsum samples is shear failure. Both the peak strength and the elastic modulus of the gypsum sample increase with increasing the loading rate，and the sample maintains a constant stress value without an obvious stress drop in the late stage of loading. When the loading rate is greater than 0.04 mm/min，the stress yield occurs at the peak value and the stress shows an increasing- decreasing-stabilizing trend，which shows that，at a high loading rate，the gypsum sample adjusts the internal structure to release strain energy and exacerbates the internal damage of the sample. The dissipated energy of the gypsum sample exceeds the elastic energy gradually in the plastic stage. After the peak stress，the dissipated energy increases rapidly，and the total energy is mainly transformed into the dissipated energy which becomes the main distribution mode. The total energy generated by the press machine after the peak value is mainly absorbed by the friction between the shear planes of the sample. When the axial strain is 0.01，the total energy and the dissipated energy tend to increase with increasing the loading rate while the elastic energy decreases. the higher the loading rate is，the larger the shear angle of the sliding surface of the gypsum sample is，and the higher the degree of failure is，which has a positive relation with the corresponding dissipated energy. The dissipation energy after the peak is the essential factor that determines the degree of shear failure of the gypsum sample.
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2020, Vol. 39 
