冻融荷载作用下砂岩损伤特性分析

发布时间：2019-04-29 20:20

【摘要】：随着我国西部大开发的进一步推进,大量岩土工程将在西部寒区进行,为确保工程的安全性,有必要研究岩石的冻融力学特性。本文从实际寒区岩体工程出发,采用理论与试验相结合的方法,较为系统地研究了冻融与荷载作用下砂岩的损伤特性。现场选取整块新鲜的大块砂岩,加工成标准圆柱形试件,分别对其进行饱水后的冻融循环试验,并在冻融循环次数为0次,5次,10次,20次以及40次时,进行围压为0MPa,2MPa,4MPa以及6MPa的三轴压缩试验。观察试验现象,得出砂岩主要破坏形式;分析讨论试验结果,得到砂岩在冻融循环和荷载作用下的力学参数,以及砂岩强度及变形特性随冻融循环次数和围压的变化规律。应用连续损伤力学理论及推广后的应变等价原理,基于岩石D-P准则,分别采用Weibull分布和Poisson分布描述砂岩微元强度的随机特性,建立砂岩的损伤模型,通过试验数据验证了模型的合理性。分析比较得出两种分布在描述砂岩压缩破坏过程中没有显著的差异,但由于采用Poisson分布所得参数表达式较为复杂,因此实用性不强。对砂岩损伤本构模型进行了修正,修正后的模型能够较好地反映砂岩应力应变曲线峰后段的变化情况,更精准的描述了砂岩残余强度;分析讨论了模型参数的物理意义;将砂岩损伤模型由常规三轴应力状态推广到真三轴应力状态,从而能够从理论上描述中间主应力对砂岩强度及力学特性的影响。建立了真三轴应力状态下,冻融砂岩的损伤模型,分析其损伤力学特性,并利用砂岩冻融循环和三轴压缩试验数据,验证了损伤模型的合理性。当围压一定时,冻融循环与荷载对砂岩造成的总损伤随着冻融循环次数的增大而增加,同时冻融循环作用使得砂岩的塑性增强,脆性减弱;当冻融循环次数一定时,砂岩的总损伤随着围压的增大而减小,且塑性特性明显增强。
[Abstract]:With the further development of the western part of China, a large number of geotechnical engineering will be carried out in the cold regions of the western part of China. In order to ensure the safety of the project, it is necessary to study the freeze-thaw mechanical properties of rocks. In this paper, the damage characteristics of sandstone under the action of freeze-thaw and load are studied systematically by the method of combining theory with test, starting from the actual rock mass engineering in cold area. The whole piece of fresh large sandstone was processed into standard cylindrical specimen, and the freezing and thawing cycle test was carried out after saturated. When the cycles of freezing and thawing were 0 times, 5 times, 10 times, 20 times and 40 times, the confining pressure was 0 MPA, 2 MPA, and 2 MPA, respectively, when the cycles of freezing and thawing were 0 times, 5 times, 10 times, 20 times and 40 times, respectively. Triaxial compression test of 4MPa and 6MPa. The main failure forms of sandstone are obtained by observing the experimental phenomena, and the mechanical parameters of sandstone under freeze-thaw cycle and load are obtained by analyzing and discussing the test results, as well as the variation of strength and deformation characteristics of sandstone with the times of freezing-thawing cycle and confining pressure. Based on the theory of continuous damage mechanics and the generalized strain equivalence principle, the damage model of sandstone is established by using the Weibull distribution and the Poisson distribution to describe the random characteristics of the strength of sandstone microelement, based on the Dp criterion of rock. The rationality of the model is verified by the experimental data. The analysis and comparison show that there is no significant difference between the two distributions in describing the process of sandstone compression failure, but the expression of parameters obtained by using Poisson distribution is rather complex, so the practicability is not strong. The damage constitutive model of sandstone is modified. The modified model can better reflect the change of the stress-strain curve of sandstone, and describe the residual strength of sandstone more accurately, and the physical significance of the model parameters is discussed, and the parameters of the model are analyzed and discussed, and the physical significance of the parameters of the model is analyzed and discussed. The damage model of sandstone is extended from the conventional triaxial stress state to the true triaxial stress state, so that the influence of intermediate principal stress on the strength and mechanical properties of sandstone can be described theoretically. The damage model of frozen-thawed sandstone under true triaxial stress is established and its damage mechanical characteristics are analyzed. The rationality of the damage model is verified by using the freezing-thawing cycle and triaxial compression test data of sandstone. When the confining pressure is constant, the total damage caused by freeze-thaw cycle and load to sandstone increases with the increase of freezing-thawing cycle times, meanwhile, the plasticity of sandstone is enhanced and the brittleness of sandstone is weakened by freezing-thawing cycle. When the number of freeze-thaw cycles is constant, the total damage of sandstone decreases with the increase of confining pressure, and the plastic properties are obviously enhanced.
【学位授予单位】：西安科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU45

【相似文献】