U.S.-Switzerland Cooperative Research on the Physics and Mechanics of Dehydration Embrittlement in Gypsum

该奖项旨在支持黄登芳教授及一名研究生和博士后与瑞士苏黎世联邦理工学院地质研究所的Kenneth Hsu教授和David Olgaard教授在实验和理论地球物理学研究方面的合作。这些研究人员对石膏脱水脆化过程的基本物理和力学有共同的兴趣。他们建议对石膏在温度、孔隙压力、应力和应变速率控制条件下的脱水速率、渗透率和孔隙度变化进行系统研究。他们将使用x射线和电子显微镜技术定量表征分解反应和孔隙结构的演变。从理论上分析了脱水反应与孔隙度、渗透率之间的关系。最终，这项实验和理论工作将使他们能够以数值方式计算逆冲构造底部的弱化和脆化程度，例如瑞士的汝拉山脉。当然，这种模拟的结果将与实地的实际地质观测结果进行比较。合作者为这项工作带来了互补的专业知识和设施，指导了劳动分工。高温、高压变形实验和x射线分析将在ETH进行。微观结构观察将在联邦理工学院和纽约州立大学石溪分校进行。渗透率测量和理论分析将在石溪进行。野外和室内观测表明，岩石的变形与变质作用密切相关。然而，大多数此类工作都是在低孔隙度结晶岩石上进行的，这些岩石的非弹性和破坏行为与温度、压力和应变速率密切相关。这些因素不足以解释多孔岩石（如石膏）或经历变质作用的岩石的行为。在进变质作用过程中，含水相的分解或压实可能导致脆性和弱化。当多孔岩石脱水时，它们的行为会有进一步的不同。拟议的研究将调查这些变化在“排水”和“不排水”形态的石膏。这些结果将大大有助于了解沉积岩构造。

This award supports Professor Teng-fong Wong and a graduate student and post-doctoral associate to collaborate in experi- mental and theoretical geophysics research with Professors Kenneth Hsu and David Olgaard of the Geological Institute of the ETH, Zurich, Switzerland. These investigators share an interest in the fundamental physics and mechanics of the process of dehydration embrittlement in gypsum. They propose to perform a systematic study of the dehydration rate, permeability and porosity change in gypsum under controlled conditions of temperature, pore pressure, stress and strain rate. They will quantitatively characterize the evolution of the decomposition reaction and pore structure using x-ray and electron microscopy techniques. Also, they will analyze theoretically the relation among the dehydration reaction, the porosity and the permeability. Ultimately, this experimental and theoretical work will enable them to compute numerically the degree of weakening and embrittle- ment at the bottom of an overthrust formation such as the Jura mountains in Switzerland. The results of such modelling will of course be compared with actual geological observations in the field. The collaborators bring complementary expertise and facilities to this work that guide the division of labor. The high temperature, high pressure deformation experiments and the x-ray analysis will be conducted at ETH. The microstructural observations will be done at ETH and SUNY at Stony Brook. The permeability measurements and theoretical analysis will be performed at Stony Brook. It has been recognized from field and laboratory observations that the deformation and metamorphism of rocks are closely linked. However, most of this work has been done on low porosity crystalline rocks for which the inelasticity and failure behavior are sensitively linked to temperature, pressure and strain rate. These factors are insufficient to explain the behavior of porous rocks, such as gypsum, or rocks that have undergone metamorphism. The decomposition or compaction of water-bearing (hydrous) phases during prograde metamorphism may lead to embrittlement and weakening. There are further differences in behavior as the porous rock is dehydrated. The proposed research will investigate these changes in both "drained" and "undrained" configurations of gypsum. The results will contribute substantially to understanding the tectonics of sedimentary rock formations.