论文标题
岩石脆性转变的微力控制
Micromechanical controls on the brittle-plastic transition in rocks
论文作者
论文摘要
岩石的流变学从局部脆性行为转变为随着压力和温度的增加而分布的塑料行为。从经验上观察到这种脆性塑料的发生在材料强度低于所谓的Goetze标准的束缚应力时发生。这样的标准适用于大多数硅酸盐，但并非所有材料都普遍。我们的目的是确定岩石在脆性塑性转变中的微物理控制和应力 - 应变行为。由于HORII和Nemat-Nasser，我们使用微型机械方法，并考虑包含滑动机翼裂缝和塑料区域的代表性体积元素。我们发现在恒定约束压力下摩擦滑动，塑性变形和裂纹开口的解决方案，并获得应力 - 应变的演化。我们表明，脆性塑性转变取决于狭窄的应力，断裂韧性和塑性应力，但同时也对摩擦系数在先前存在的缺陷方面进行了批判性。摩擦低的材料预计会更脆弱，并且经历了比Goetze标准预期的更高压力下的塑性流过渡。 Goetze标准在岩石中脆性塑性过渡的总体成功可能是由于大多数岩石形成矿物质的韧性，高强度和中等摩擦系数特征而产生的。
The rheology of rocks transitions from a localized brittle behaviour to distributed plastic behaviour with increasing pressure and temperature. This brittle-plastic is empirically observed to occur when the material strength becomes lower than the confining stress, which is termed Goetze's criterion. Such a criterion works well for most silicates but is not universal for all materials. We aim to determine the microphysical controls and stress-strain behaviour of rocks in the brittle-plastic transition. We use a micro-mechanical approach due to Horii and Nemat-Nasser, and consider representative volume elements containing sliding wing-cracks and plastic zones. We find solutions for frictional slip, plastic deformation and crack opening at constant confining pressure, and obtain stress-strain evolution. We show that the brittle-plastic transition depends on the confining stress, fracture toughness and plastic yield stress but also critically on the friction coefficient on preexisting defects. Materials with low friction are expected to be more brittle, and experience transition to fully plastic flow at higher pressure than anticipated from Goetze's criterion. The overall success of Goetze's criterion for the brittle-plastic transition in rocks is likely arising from the low toughness, high strength, and medium friction coefficient character of most rock forming minerals.
