基于残余强度的冻融受荷岩石损伤破坏特性研究

发布时间：2018-03-05 06:11

本文选题：残余强度　切入点：损伤阀值　出处：《西安科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着我国经济建设的发展,寒区的岩土工程数量及规模不断扩大,冻融灾害是亟待解决的关键问题。研究岩石在冻融条件下的损伤机理和破坏条件,可以为有效的指导工程建设安全生产提供依据。本文采用宏细观方法与统计学方法相结合,对冻融与荷载条件下岩石的损伤模型及强度准则进行了较为深入的研究。将受荷岩石抽象为损伤和未损伤两部分材料组成,损伤部分可承受残余强度的力;基于Weibull统计分布和Drucker-Prager准则,建立了可反映岩石残余段变形特征的损伤模型;利用峰值点法求解得到模型参数的理论表达式,并分析其物理意义。针对目前常用引入修正因子建立的岩石损伤模型,就反映岩石残余段变形特征的适用性进行了对比,并从数学形式上进行了分析说明。考虑冻融因素和荷载因素对岩石的影响,基于总损伤变量的概念,建立了冻融循环与荷载共同作用下的岩石损伤模型。分析讨论了总损伤变量和总损伤演化率随围压和冻融次数的变化规律。当冻融循环次数增加时,岩石损伤程度加剧,宏观力学性能劣化,抗压强度和残余强度减小,破坏方式逐渐趋向于延性破坏;当围压增大时,岩石损伤劣化程度减小,抗压强度和残余强度增大,脆性特征逐渐消失,延性特征逐渐明显。通过分析岩石应力应变关系曲线在峰值点处的几何特征,采用多元函数求全微分的方法建立了考虑冻融效应的岩石强度准则。该准则可用于表征不同冻融循环次数下岩石在极限状态时内部应力参量之间的关系,且能反映强度莫尔包络线的曲线性质。当冻融循环次数增多时,强度莫尔包络线曲线性质更为显著,表明该准则适合冻融受荷岩石强度的判定;据此重新设定损伤阀值,建立新型冻融受荷岩石的损伤模型。与试验数据进行对比分析,结果表明,新型的冻融受荷模型无法较好的反映岩石塑性屈服阶段,但在峰后段和残余段仍与试验曲线吻合较好。
[Abstract]:With the development of economic construction in China, the number and scale of geotechnical engineering in cold regions are expanding, and freeze-thaw disasters are the key problems to be solved. The damage mechanism and damage conditions of rocks under freezing and thawing conditions are studied. It can provide the basis for guiding engineering construction safety production effectively. This paper combines macroscopical method with statistical method. The damage model and strength criterion of rock under freeze-thaw and load conditions are studied deeply. The loaded rock is abstracted into two parts: damaged and undamaged, and the damage part can bear the force of residual strength. Based on the Weibull statistical distribution and the Drucker-Prager criterion, a damage model reflecting the deformation characteristics of the residual rock is established, and the theoretical expression of the model parameters is obtained by using the peak point method. And its physical significance is analyzed. According to the rock damage model established by introducing correction factor, the applicability of reflecting the deformation characteristics of residual rock is compared. Considering the influence of freeze-thaw factor and load factor on rock, based on the concept of total damage variable, The damage model of rock under the combined action of freeze-thaw cycle and load is established. The variation law of total damage variable and total damage evolution rate with confining pressure and freeze-thaw times is discussed. When the freeze-thaw cycle number increases, the damage degree of rock is aggravated. When the confining pressure increases, the damage deterioration degree of rock decreases, the compressive strength and residual strength increase, and the brittle characteristics gradually disappear, when the confining pressure increases, the compressive strength and residual strength decrease, the failure mode tends to ductile failure, and when the confining pressure increases, the damage degradation degree decreases, the compressive strength and residual strength increase, and the brittle characteristics gradually disappear. By analyzing the geometric characteristics of the stress-strain relationship curve at the peak point, A rock strength criterion considering freeze-thaw effect is established by using multivariate function to solve the total differential equation. The criterion can be used to characterize the relationship between the internal stress parameters of rock under different freezing and thawing cycles under the limit state. When the number of freeze-thaw cycles increases, the properties of intensity-moire envelope curves are more obvious, which indicates that the criterion is suitable for judging the strength of frozen and thawed rocks, and the damage threshold is reset accordingly. A new damage model of frozen and thawed rock is established. The results show that the new model can not reflect the plastic yield stage of rock. But at the back of the peak and the residual section, it still agrees well with the test curve.
【学位授予单位】：西安科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O346.5

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