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Experimental study of compaction localization in carbonate rock and constitutive modeling of mechanical anisotropy
International Journal for Numerical and Analytical Methods in Geomechanics ( IF 4 ) Pub Date : 2022-07-20 , DOI: 10.1002/nag.3418
Ghassan Shahin 1 , Athanasios Papazoglou 2 , Ferdinando Marinelli 3 , Gioacchino Viggiani 2 , Giuseppe Buscarnera 1
Affiliation  

Sedimentary rocks are inherently anisotropic and prone to strain localization. While the influence of rock anisotropy on the brittle/dilative regime has been studied extensively, its influence on the ductile/compactive regime is much less explored. This paper discusses the anisotropic behavior of a high-porosity carbonate rock from central Europe (the Maastricht Tuffeau). A set of triaxial tests with concurrent x-ray tomography has been performed at different confining pressures. The anisotropic characteristics of this rock have been investigated by testing samples cored at different inclinations of the bedding, thus revealing non-negligible effects of the coring direction on yielding and compaction behavior. Specifically, samples cored perpendicular to bedding display higher strength and longer stages of post-yielding deformation before manifesting re-hardening. Despite such alterations of the inelastic response, Digital Image Correlation has revealed that the strain localization mode is independent of the coring direction, thus being primarily affected by the confinement level. To capture the observed interaction between material anisotropy and compaction behavior at the continuum-scale, an elastoplastic constitutive law has been proposed. For this purpose, a set of tensorial bases has been introduced to replicate how the oriented rock fabric modulates the yielding and plastic flow characteristics of the material. The analyses show that the impact of the coring direction on yield function and plastic flow rule is fundamentally different, thus requiring the use of distinct projection strategies (a strategy here defined heterotopic mapping). The performance of the model, studied through parametric analyses and by calibrating the experimental results, illustrates the improved capability of the proposed constitutive approach when applied to strongly anisotropic porous rocks.

中文翻译:

碳酸盐岩压实局部化试验研究及力学各向异性本构建模

沉积岩本质上是各向异性的,容易发生应变局部化。虽然岩石各向异性对脆性/膨胀状态的影响已被广泛研究,但其对延性/压实状态的影响却鲜为人知。本文讨论了来自中欧的高孔隙度碳酸盐岩(马斯特里赫特凝灰岩)的各向异性行为。已经在不同的围压下进行了一组同时进行 X 射线断层扫描的三轴测试。该岩石的各向异性特性已经通过测试在不同层理倾斜度上取芯的样品进行了研究,从而揭示了取芯方向对屈服和压实行为的不可忽略的影响。具体来说,垂直于层理取芯的样品在再次硬化之前显示出更高的强度和更长的屈服后变形阶段。尽管非弹性响应发生了这种变化,但数字图像相关性显示应变定位模式与取芯方向无关,因此主要受限制水平的影响。为了在连续尺度上捕捉观察到的材料各向异性和压实行为之间的相互作用,已经提出了弹塑性本构定律。为此,引入了一组张量基础来复制定向岩石织物如何调节材料的屈服和塑性流动特性。分析表明,取芯方向对屈服函数和塑性流动规律的影响是根本不同的,因此需要使用不同的投影策略(此处定义的异位映射策略)。通过参数分析和校准实验结果研究了模型的性能,说明了所提出的本构方法在应用于强各向异性多孔岩石时的改进能力。
更新日期:2022-07-20
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