Chemical and mechanical processes are coupled in many geological and geochemical environments. Reactive processes anneal defects and restructure grain boundaries, modifying their elastic properties, levels of internal friction, wave propagation rates and fracture behaviors. The nature of these changes is, however, contingent on the initial state of the rock. In this study, impulse excitation was used to measure changes in mechanical properties as a function of dry and steam heating time at 300 °C for three carbonate rocks: Carrara marble, Carthage marble (Burlington Limestone), and Texas Cream limestone (Edwards limestone), with initial porosities of about 1 %, 3 %, and 27 %, respectively. Frequency-dependent phenomena along with mineral recrystallization were observed. This was coupled with small-angle X-ray and neutron scattering analysis to determine the relationship between changes in bulk mechanical and microstructural properties. An observed decrease in both the Young's and shear moduli in the experimental limestones as a function of heating time reflects and quantifies a reduction in the stiffness of the rock due to annealing. The internal friction of the samples first increases then decreases with reaction time, reflecting defect annealing, but this was balanced against grain boundary dissolution apparently driven by condensation of steam in the confined grain-boundary environment. This suggests an increase in the boiling point under confinement leading to dissolution, increased porosity and widening of the grain boundaries. In addition, comparison of small-angle X-ray and neutron scattering results suggests that it is inappropriate to assume that pores are empty for quantitative analysis of typical small-angle scattering samples.

中文翻译：

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退火和晶界控制对石灰石和大理石力学性能的影响


化学和机械过程在许多地质和地球化学环境中是耦合的。反应过程退火缺陷并重组晶界，改变其弹性特性、内部摩擦水平、波传播速率和断裂行为。然而，这些变化的性质取决于岩石的初始状态。在这项研究中，脉冲激发用于测量三种碳酸盐岩在 300 °C 下干加热和蒸汽加热时间的变化：卡拉拉大理石、迦太基大理石（伯灵顿石灰石）和德克萨斯奶油石灰石（爱德华兹石灰石），初始孔隙率分别约为 1 %、3 % 和 27 %。观察到频率依赖性现象以及矿物再结晶。这与小角 X 射线和中子散射分析相结合，以确定体力学和微观结构特性变化之间的关系。观察到的实验石灰石中的杨氏模量和剪切模量随加热时间的函数而降低，这反映并量化了由于退火而导致的岩石刚度降低。样品的内耗随反应时间的增加先增加，然后减少，反映了缺陷退火，但这与显然由密闭晶界环境中蒸汽冷凝驱动的晶界溶解相平衡。这表明在约束下沸点增加，导致溶解、孔隙率增加和晶界变宽。此外，小角 X 射线和中子散射结果的比较表明，对于典型小角散射样品的定量分析，假设孔隙是空的并不合适。