【摘要】 由岩石缺陷(裂隙、微结构和颗粒接触面等)引起的在应力–应变关系测量中偏离胡克定律的非线性弹性滞后行为,是普遍存在的;应力与轴向应变或径向应变之间存在着滞后,轴向应变与横向应变之间也存在滞后。通过实验得知,在加卸载阶段弹性模量随应变变化趋势各不相同,导致瞬时弹性模量与应变成不对称蝴蝶结形;以3种不同黏滞系数的孔隙液体饱和的合肥砂岩、自贡长石砂岩和大理大理岩,分别进行不同频率的循环加载实验,获得随孔隙流体黏滞系数增大,蝴蝶结形张角增大,滞后增强,随频率增高,弹性模量增大。提出以蝴蝶结形张角的大小来定量度量滞后的程度,并将蝴蝶结张角与度量衰减的耗散角进行了对比研究。蝴蝶结张角和耗散角的值均随饱和流体黏滞系数的增大而增大,滞后增强,滞回圈面积增大,衰减增大;随正弦波频率提高,蝴蝶结张角、耗散角增大,弹性模量增大,弹性模量的频散增强。在同一岩石中蝴蝶结张角和耗散角随孔隙液体黏滞系数和加载频率的变化规律与以往其他实验的结果是一致的。蝴蝶结张角与耗散角在衡量滞后方面具有同等价值,但二者的数值并不相等,对二者在滞后的物理机制和滞后定义方面的意义进行讨论。更多还原

【Abstract】 The nonlinear elastic hysteric behavior,which is off the Hooke′s law and caused by the presence of structural defects in rock,such as microcracks and grain boundaries,universally exists in the measurement of stress-strain relation.The instantaneous elastic moluli of rocks in both loading stage and unloading stage vary with stain,which results in lopsided bowknot shape of instantaneous elastic modulus.Hefei sandstone,Zigong feldspar sandstone and Dali marble,saturated in 3 types of fluids with different viscosity coefficients,are tested with various frequencies by cyclic loading experiments.The angle between the loading modulus and the unloading modulus of bowknot shape is suggested to measure hysteresis of rocks,and to compare it with dissipative angle which measures hysteresis originally.Both bowknot angle and dissipative angle enhance as the area of hysteresis loop increases,and attenuation enhances as viscosity coefficient of pore fluid increases.With both the bowknot angle and dissipative angle increasing,modulus increases,and dispersion of modulus enhances as frequency increases.The variety of bowknot angle and dissipative angle with viscosity coefficient of pore fluid and cyclic loading frequency is consistent with the results of other experiments.The conclusion is drawn that the bowknot angle and dissipative angle are equivalent in measuring hysteresis of rock but are not in numerical value.The physical mechanism and significance of definition of hysteresis are discussed.更多还原