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循环加卸载条件下花岗岩力学特性及疲劳损伤演化研究

Mechanical properties and fatigue damage evolution of granite under cyclic loading and unloading conditions

  • 摘要: 为了研究岩石在循环加卸载下的力学特性及能量损伤演化规律,设计了5种花岗岩三轴循环加卸载试验。基于试验结果,详细分析了不同围压的循环加卸载模式下的总能量、弹性应变能和耗散能的演化特征及相互关系,建立了岩石损伤耗散能与循环加载次数及围压的耦合演化方程。结果表明:①当载荷小于峰值应力时,加载阶段的弹性模量小于卸载阶段的弹性模量;②峰值应力前,载荷所产生的能量主要表现为弹性应变能,而峰值应力后,载荷所产生的能量主要表现为耗散能;③随着围压的增加,岩石弹性应变能及耗散能增加;④循环加卸载作用下,岩石的耗散能与围压及加卸载循环次数有明显相关性,可以用非线性曲面进行拟合,可为定量分析循环加卸载过程中岩石损伤提供参考。

     

    Abstract: To analyze the evolution law of mechanical properties and energy during the cyclic loading and unloading process,five kinds of granite triaxial cyclic loading and unloading experiments have been performed. Based on the experimental results,the evolution characteristics and their interrelationship of total absorption energy,elastic strain energy and dissipated energy under different confining pressure have been analyzed in detail,and the coupling evolution equation of rock damage dissipated energy changes with cycles loading and unloading times and confining pressure are established. The results show that:① When the load is less than the peak stress,the elastic modulus in the loading stage is smaller than that in the unloading stage;② Before the peak stress,the energy generated by the load is mainly shown as elastic strain energy,while after the peak stress,the energy generated by the load is mainly expressed as dissipated energy;③ As the confining pressure increases,rock elastic strain energy and dissipated energy increases;④ Under cyclic loading-unloading,the dissipated energy of the rock has a significant correlation with the confining pressure and the cycle loading and unloading times. Non-linear curved surfaces can be used for fitting the relationship. This finding can provide a basis for quantitative analysis of rock damage during cyclic loading and unloading.

     

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