基于弹性模量退化的冻土动力损伤特性研究

为研究冻土在不同温度下的弹性模量退化与动力特佂，通过对不同负温条件下冻土试样进行循环加、卸载试验，获得其在动荷载作用下的应力-应变滞回曲线与疲劳损伤寿命。按照疲劳寿命与应力幅之间的关系确定了冻土在不同温度下的疲劳损伤参数。根据冻土的弹性模量退化规律提出了动弹模衰减控制方程并建立了冻土唯象疲劳损伤模型。根据冻土实测的循环加卸载滞回曲线特征，提出了理想和非理想滞回圈情况下阻尼比联合分析方法；基于Kelvin模型建立了滞回圈演化规律与弹性模量退化及加载时间的数学联系。研究发现：考虑了动弹模衰减影响的唯象疲劳损伤模型描述了冻土的加速疲劳损伤特征；理想滞回与非理想滞回阻尼比联合分析方法考虑滞回圈的实际演化特征；基于弹性模量退化的Kelvin流变模型建立了滞回圈曲线与加、卸载时间的数学联系。

Study on dynamic damage mechanism of frozen soil based on elastic modulus degradation

In order to study the elastic modulus degradation and dynamic characteristics of permafrost at different temperatures, the stress-strain hysteresis curve and fatigue damage life under dynamic load were obtained by cyclic loading and unloading test of frozen soil samples under different below-zero temperature conditions. Fatigue damage parameters of permafrost at different temperatures were determined according to the relationship between fatigue life and stress amplitude. According to the law of elastic modulus degradation of permafrost, the governing equation of dynamic model was proposed and the phenomenological model of fatigue damage of permafrost was established. According to the characteristics of cyclic loading and unloading hysteresis curve measured by permafrost, the method of joint analysis of damping ratio under ideal and non-ideal hysteresis loops was proposed. Based on the Kelvin model, the mathematical relationship between the evolution of the hysteresis loop and the elastic modulus degradation and loading time was established. The study shows that: the phenomenological fatigue damage model, which takes into account the effects of the elastic modulus attenuation, describes the accelerated fatigue damage characteristics of permafrost. Equivalent hysteresis and non-ideal hysteresis damping ratio analysis method is good for taking account of the actual evolutionary characteristics of hysteresis loops. The Kelvin rheological model based on elastic modulus degradation establishes the mathematical relationship between the hysteresis loop and the unloading time.