Experimental study on physico-mechanical effects of high temperature dehydrated gypsum rock
SU Chengdong1，2，WEI Sijiang1，2，XU Chongbang3，SU Faqiang1，2
(1. School of Energy Science and Engineering，Henan Polytechnic University，Jiaozuo，Henan 454003，China；2. Collaborative Innovation Center of Coal Work Safety，Henan Province，Jiaozuo，Henan 454003，China；3. Research Institute of Highway Ministry of Transport，Beijing 100088，China)
Abstract：In order to investigate the effect of high temperature dehydration on physical and mechanical properties of natural gypsum rock，standard rock samples contained different crystal water were prepared at 220 ℃ within a certain time and tested with scanning electron microscope，ultrasonic wave and conventional triaxial compression. The influence of the dehydration time on physical and mechanical behaviors of gypsum rock，including microstructure，porosity，longitudinal wave velocity，conventional triaxial compressive strength，elastic modulus，peak strain，cohesion and friction angle，was analyzed. The results are showed as follows. High temperature effect on gypsum rock is an extreme complex physical and chemical process. Gypsum rock can be obviously weakened by high temperature dehydration. With increasing the dehydration time，the crystal structure and shape of gypsum rock change gradually and the numbers of micro-cracks and micro-voids increase gradually，which leads to the deterioration of the physical and mechanical properties of gypsum rock. The dehydration amount，the apparent density and the porosity are nonlinear with the dehydration time. The dehydration rate of gypsum rock is larger within 6 hours while decreases within 6 to 24 hours. P-wave velocity of gypsum samples decreases to some extent due to high temperature dehydration. The damage factor decreases linearly with the porosity within 6 hours but changes little after 6 hours. The deformation characteristics of gypsum rock under triaxial compression are influenced by the confining pressure and the high temperature dehydration time. The influence of the dehydration time on the deformation parameters of gypsum rock samples including the elastic modulus and the deformation modulus is far greater than that on the confining pressure within 4 hours，but the confining pressure has little influence on the elastic modulus and the deformation modulus. With increasing the confining pressure and the dehydration time，the brittleness of the specimens decreases but the plasticity increases. Triaxial peak strength of the samples increases monotonously with the confining pressure，which accords with Coulomb strength criterion. The strength of gypsum rock material is negatively correlated with the dehydration time without considering the influence of the confining pressure. The failure mode of gypsum rock samples has no direct relationship with the confining pressure and is more complex with longer dehydration time.
苏承东1，2，韦四江1，2，许崇帮3，苏发强1，2. 高温脱水石膏岩物理力学效应的试验研究[J]. 岩石力学与工程学报, 2019, 38(2): 254-266.
SU Chengdong1，2，WEI Sijiang1，2，XU Chongbang3，SU Faqiang1，2. Experimental study on physico-mechanical effects of high temperature dehydrated gypsum rock. , 2019, 38(2): 254-266.
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2019, Vol. 38 
