Abstract

Fatigue tests under high static pre-stress loads can provide meaningful results to better understand the time-dependent failure characteristics of rock and rock-like materials. However, fatigue tests under high static pre-stress loads are rarely reported in previous literature. In this study, the rock specimens were loaded with a high static pre-stress representing 70% and 80% of the uniaxial compressive strength (UCS), and cyclic fatigue loads with a low amplitude (i.e., 5%, 7.5% and 10% of the UCS) were applied. The results demonstrate that the fatigue life decreased as the static pre-stress level or amplitude of fatigue loads increased for different rock types. The high static pre-stress affected the fatigue life greatly when the static pre-stress was larger than the damage stress of rocks in uniaxial compression tests. The accumulative fatigue damage exhibited three stages during the fatigue failure process, i.e., crack initiation, uniform velocity, and acceleration, and the fatigue modulus showed an “S-type” change trend. The lateral and volumetric strains had a much higher sensitivity to the cyclic loading and could be used to predict fatigue failure characteristics. It was observed that volumetric strain \(\varepsilon _{{\text{v}}}\) = 0 is a threshold for microcracks coalescence and is an important value for estimating the fatigue life.

Article highlights

• Fatigue mechanical performance of high static pre-stressed rocks were evaluated.

• The results demonstrate that the fatigue life decreased as the static pre-stress level increased and the static pre-stress affected the fatigue life more than the amplitude of fatigue loads.

• The volumetric strain of zero before fatigue loading is a threshold for fatigue failure of rocks under high static stress.

中文翻译：

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砂岩、大理石、花岗岩在高静应力下的低振幅疲劳性能

摘要

高静态预应力载荷下的疲劳试验可以提供有意义的结果，以更好地了解岩石和类岩石材料的时间相关破坏特性。然而，在以前的文献中很少报道在高静态预应力载荷下的疲劳试验。在这项研究中，岩石试样加载了代表 70% 和 80% 单轴抗压强度 (UCS) 的高静态预应力，以及低振幅（即 5%、7.5% 和 10%）的循环疲劳载荷。 UCS) 的应用。结果表明，不同岩石类型的疲劳寿命随着静态预应力水平或疲劳载荷幅度的增加而降低。在单轴压缩试验中，当静预应力大于岩石破坏应力时，高静预应力对疲劳寿命影响较大。疲劳破坏过程中累积疲劳损伤呈现裂纹萌生、匀速和加速三个阶段，疲劳模量呈“S型”变化趋势。横向和体积应变对循环载荷具有更高的敏感性，可用于预测疲劳失效特性。观察到体积应变\(\varepsilon _{{\text{v}}}\)  = 0 是微裂纹​​合并的阈值，是估计疲劳寿命的重要值。

文章亮点

• 评价了高静力预应力岩石的疲劳力学性能。

• 结果表明，疲劳寿命随着静态预应力水平的增加而降低，并且静态预应力对疲劳寿命的影响大于疲劳载荷的幅值。

• 疲劳加载前的零体积应变是岩石在高静应力下疲劳破坏的阈值。