Microscopic Study on Mechanisms of Brittle Fracture and Ductile Deformation in Rocks under High Confining Pressures.

四个英国破碎的岩石的微观结构和一个破碎的岩石已经被研究过了。它们与在三次实验中观察到的机械性能相比较，达到房间温度下的3 GPa压缩压力。四个低强度岩石的断裂机制（花岗岩、加布罗、沙丘和eclogite）在压缩强度时从低压力到高压力类型变得等于框架强度。“低压力类型”展示了对良好记录的小碎片的同等功能。高压力类型与它不同：强度增加在增加确认压力的较低增加率; AE活动在切割前没有快速增加，但在一个突然的最终切割下恒定地跟随;微裂纹没有集中关闭，主要故障在45处被清晰和定向到最大压力方向。“高压力类型断裂可能会产生与Brittle和Ductile政权之间过渡性的一个，并考虑到在高温实验中发现的缺陷特征的相似性。”估计的大小对压力下强度的影响给出了一个建议，即晶体中的碎片可能是高压力类型的地震应该对它们进行建模。在结壳中可能的故障处理包括第一个故障处理和迁移的故障处理是模型化的：一种干燥的、精细的、粗糙的、有7%污染的碱性碱，在半导体制度中，展示了致命的变形行为。在较高压力水平的渐进式阶段，发现流动机制可以从权力法中改变，并在2 GPa确认压力的3比1。这是从残留的极封闭和过度膨胀的部分中找到的结果。-10^5 Pa·s的可见度下降被估计为与应变率对应的机制变化有关，用于结壳和地幔。

Microstructures of four brittle-fractured rocks and a cataclastically-deformed rock were studied. They were compared with the mechanical properties which had been observed in the triaxial experiments up to 3 GPa confining pressure at room temperature.Fracture mechanism of four low-porosity rocks (granite, gabbro, dunite and eclogite) changed from the low- to high-pressure types when the compressive strength became equal to the frictional strength. The low-pressure type exhibited the equivalent features to the well-documented brittle fracture. The high-pressure type was different from it: the strength increases linearly at lower increasing rate with increasing confining pressure; the AE activity does not increase rapidly before fracture but stays constant followed by a sudden final fracture; and microcracks are not concentrated close tothe main fault being sharp and oriented at 45 to the maximum stress direction. The high-pressure type fracture might correspond to the transitional one between brittle and ductile regimes, considering the similarity in the faulting features to those found in high temperature experiments. Estimated size effect on strength under pressure gave the suggestion that fracture in the crust might be of the high-pressure type which earthquakes should be modeled upon. Possible faulting processes in the crust including the first faulting and movement of exisiting faults were modeled.A dry fine-grained basalt with 7% porosity, in the ductile regime, exhibited cataclastic deformation behavior. In the progressive stage of granulation at higher stress levels, the flow mechanism was found to change from the power-law creep with stress exponent of 3 to 1 at 2 GPa confining pressure. It was found to results from the remaining-pore closure and pervasion of highly granulated portions. The viscosity drop of -10^5 Pa・s was estimated associated with the mechanism change at the strain rate corresponding to that for the crust and mantle.