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利用疲劳损伤理论来研究冻融循环条件下岩石的损伤累积在理论上是可行的。主要分析冻融疲劳损伤模型在计算自然条件下岩石冻融损伤时面临的主要问题,包括复杂多变的自然条件下如何简化、近似冻融循环作用,如何选取合适的物理量来计算损伤变量,及如何计算多种机制作用下岩石的冻融损伤。经过分析认为:研究自然条件下的昼夜循环和年度循环对人类工程活动意义最大,根据岩石中饱和度的高低和岩石中未冻水迁移速率的快慢,可分别将昼夜循环和年度循环划分并等效为高周或低周疲劳荷载;冻融循环条件下岩石孔隙率的变化可直接反映冻融损伤的特征,利用缺陷面积和残余应变定义的损伤变量其本质是相同的,均可用孔隙率计算得来;建立冻融循环作用下砂岩的高周疲劳损伤模型和低周疲劳损伤模型,利用模型进行分析表明,在计算自然条件下岩石的冻融损伤时高周疲劳荷载的作用是不可忽略的,并且低周疲劳和高周疲劳荷载的作用顺序具有显著的影响。
It is theoretically feasible to use the theory of fatigue damage to study the damage accumulation of rock under freezing-thawing cycles. This paper mainly analyzes the main problems that the freeze-thaw fatigue damage model faces in calculating freezing and thawing damage of rock under natural conditions, including how to simplify and approximate the freeze-thaw cycles under complex and changeable natural conditions and how to select appropriate physical quantities to calculate the damage variables. How to Calculate the Freezing and Thawing Damage of Rock under Various Mechanisms. After analysis, it is concluded that the study of day and night cycle and annual cycle under natural conditions has the greatest significance to human engineering activities. According to the degree of saturation in rocks and the speed of unfrozen water migration in rocks, the diurnal cycle and annual cycle can be divided The results show that the change of rock porosity under freeze-thaw cycles can directly reflect the characteristics of freeze-thaw damage. The damage variables defined by the defect area and residual strain are of the same nature and can be calculated by porosity The model of high cycle fatigue damage and low cycle fatigue damage of sandstone under the action of freeze-thaw cycle was established. The model analysis shows that the effect of high cycle fatigue load can not be ignored in the calculation of freezing and thawing damage of rock under natural conditions , And the order of action of low-cycle fatigue and high-cycle fatigue load has a significant effect.