Damage amplification during repetitive seismic waves in mechanically loaded rocks.
Damage amplification during repetitive seismic waves in mechanically loaded rocks.
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DOI：
10.1038/s41598-022-26721-x
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发表时间：
2023-01-23
影响因子：
4.6
通讯作者：
中科院分区：
文献类型：
--
作者：
应力积累和释放的循环是构造活动行星所固有的。这种应力振荡会产生应变和损伤，促使机械加载的岩石和材料失效。在这里，我们调查，在单轴条件下，损伤积累和削弱所造成的时间依赖性蠕变（在60，65，和70%的岩石的预期破坏应力）和重复应力振荡（± 2.5，5.0或7.5%的蠕变载荷），模拟地震的震动频率约1.3 Hz的火山岩。结果表明，应力振荡传递更多的损害比恒定的负载，偶尔促使样品失效。蠕变应力和应力振荡的大小与我们的斑状安山岩的力学响应，暗示渐进微裂纹的永久非弹性应变的原因。显微结构研究表明，实验后岩石中的裂缝较长，裂缝密度较高。我们对蠕变引起的非弹性应变信号进行反卷积，以量化每个单独的振荡事件所造成的损伤量，表明应变的大小通常在前几次振荡时最大;在预先存在的损伤和/或振荡的振幅有利于微裂纹朝向系统规模故障的聚结的情况下，无论蠕变条件如何，所记录的应变信号显示出随着振荡次数的增加而急剧增加。我们的结论是，在地震过程中重复的应力振荡可以放大的损坏量，否则机械加载的材料，从而加剧其削弱，一个过程，可能会影响自然或工程结构。我们专门讨论火山的情况下，没有批发故障，应力振荡可能会产生损害，这可能会，例如，改变孔隙流体通道，修改应力分布和影响未来的脆弱性破裂和相关的危害。
Cycles of stress build-up and release are inherent to tectonically active planets. Such stress oscillations impart strain and damage, prompting mechanically loaded rocks and materials to fail. Here, we investigate, under uniaxial conditions, damage accumulation and weakening caused by time-dependent creep (at 60, 65, and 70% of the rocks’ expected failure stress) and repeating stress oscillations (of ± 2.5, 5.0 or 7.5% of the creep load), simulating earthquakes at a shaking frequency of ~ 1.3 Hz in volcanic rocks. The results show that stress oscillations impart more damage than constant loads, occasionally prompting sample failure. The magnitudes of the creep stresses and stress oscillations correlate with the mechanical responses of our porphyritic andesites, implicating progressive microcracking as the cause of permanent inelastic strain. Microstructural investigation reveals longer fractures and higher fracture density in the post-experimental rock. We deconvolve the inelastic strain signal caused by creep deformation to quantify the amount of damage imparted by each individual oscillation event, showing that the magnitude of strain is generally largest with the first few oscillations; in instances where pre-existing damage and/or the oscillations’ amplitude favour the coalescence of micro-cracks towards system scale failure, the strain signal recorded shows a sharp increase as the number of oscillations increases, regardless of the creep condition. We conclude that repetitive stress oscillations during earthquakes can amplify the amount of damage in otherwise mechanically loaded materials, thus accentuating their weakening, a process that may affect natural or engineered structures. We specifically discuss volcanic scenarios without wholesale failure, where stress oscillations may generate damage, which could, for example, alter pore fluid pathways, modify stress distribution and affect future vulnerability to rupture and associated hazards.
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影响因子：
5.2
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