【摘要】 为了探讨高温脱水对天然石膏岩物理力学效应的影响,将天然石膏岩在高温220℃控制脱水时间制取含不同结晶水石膏岩试样,分别对石膏岩试样进行扫描电镜、超声波测试和常规三轴压缩试验,分析高温脱水时间对石膏岩微观结构、孔隙率、纵波波速、三轴抗压强度,弹性模量、峰值应变、黏结力和内摩擦角的影响。结果表明:高温作用对石膏的作用是极其复杂物理化学过程,高温脱水对石膏岩具有明显弱化作用,随着高温脱水时间的增加,石膏岩内部晶体结构和形状逐渐发生变化,试样内部微裂纹、微孔洞的数量逐渐增多,导致其物理力学性能不断劣化;在高温220℃石膏岩脱水量、视密度和孔隙率与脱水时间呈非线性关系,在0～6 h以内裂解脱水速率较快,在6～24 h范围内脱水速率有所减缓。高温脱水后石膏试样纵波波速均有不同程度降低,在0～6 h以内损伤因子随孔隙率增加而单调降低,两者大致呈线性关系,超过6h以后脱水石膏岩损伤因子变化不大;石膏岩三轴压缩全程的变形特征受围压和高温脱水时间的共同影响,脱水时间0～4 h对石膏岩试样变形参数的影响远大于对围压的影响,超过4h以后脱水时间、围压对石膏岩弹性模量和变形模量的影响不大,随着围压与脱水时间的增加脆性减弱塑性增强;石膏岩试样三轴峰值强度随围压增大而单调增加,符合Coulomb强度准则。高温脱水对石膏岩具有明显弱化作用,扣除围压影响后石膏岩材料强度与脱水时间呈负相关;石膏岩试样破坏形态与围压高低没有直接关系,脱水时间越长破坏形态越复杂。更多还原

【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.更多还原