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为深入研究循环加卸载作用下岩体的变形规律,针对三峡库区砂岩进行了56组循环加卸载试验。根据试验的不同步现象,对应力–应变滞后概念进行修正:(1)应力超前于应变和应力滞后于应变现象共存,故将“应力–应变滞后现象”更名为“应力–应变不同步现象”更为合理;(2)在应力–应变不同步现象的基础上,应考虑应力速率–应变速率的不同步现象。通过分析循环加卸载试验的不同步机制,提出应力–应变吸引点、应力速率–应变速率吸引点、应力–应变补偿机制和应力速率–应变速率补偿机制4个概念,并且得到:应力–应变同步与应力速率–应变速率同步不能同时出现;不同步现象是必然而同步仅存在于某一时刻点;应力–应变处于螺旋式循环递进的过程。基于循环加卸载试验,首次发现应力速率–应变速率不同步现象,在不同步现象中提出了3个不同步阶段的定义,并通过分析预测变形速率–实际变形速率、表观弹性模量以及岩样的瞬时泊松比随时间的变化规律,提出3种对不同步阶段定量判别的方法。此外,基于同频率不同峰值强度下试验得到,随着峰值强度f(t)的增加,岩样的E(t)值逐渐增加,式E(t)?af(t)?b吻合度也逐渐增加。
In order to further study the deformation law of rock mass under cyclic loading and unloading, 56 cyclic loading and unloading tests were carried out for the sandstone in the Three Gorges reservoir area. According to the phenomenon of non-synchronous test, the concept of stress-strain hysteresis is revised: (1) stress is ahead of strain and stress lag in coexistence of strain phenomenon, so “stress-strain hysteresis” is changed to “stress- Synchronous phenomenon ”is more reasonable; (2) On the basis of the phenomenon of non-synchronous stress-strain, we should consider the stress-strain-asynchronous phenomenon. By analyzing the asynchronous mechanism of cyclic loading and unloading test, four concepts of stress-strain attraction point, stress-strain rate attraction point, stress-strain compensation mechanism and stress rate-strain rate compensation mechanism are proposed and obtained: And the stress-strain rate synchronization can not occur at the same time; the phenomenon of non-synchronization is inevitable and the synchronization exists only at a certain moment; the stress-strain is in the progress of the spiral cycle. Based on the cyclic loading and unloading tests, the phenomenon of asynchronization of stress rate and strain rate was first discovered. Three unsynchronized stages were defined in the phenomenon of asynchronization. By analyzing and predicting the deformation rate, the actual deformation rate, the apparent elastic modulus, Like instantaneous Poisson’s ratio changes with time, three methods of quantitative discrimination of unsynchronized stages are proposed. In addition, based on the experiments with different peak intensities at the same frequency, the E (t) values of rock samples gradually increase with the increase of peak intensity f (t), and the agreement of E (t)? Af (t) increase.