Mechanical Behaviour of Rocks Under High Pressure Conditions

Knowledge of the mechanical properties of rocks at high pressure and temperature is fundamental not only for material science but also for earth science, such as for solving the mechanism of earthquakes and tectonic processes. For example, physical bases of the earthquake prediction based on the rock mechanics have been proposed, and extensive seismological, geophysical and geochemical observations have been conducted to find precursory phenomena before large earthquakes. However, we cannot help telling for the present that we do not have sufficient knowledge of an effective and reliable method for earthquake prediction. The book is mainly concerned with comprehensive source of information on the mechanical properties and behavior of rocks under high pressure that scans current state-of-the-art knowledge and shows contribution in establishing an experimental basis for the understanding of the mechanism of rock deformation in the earth's interior. The book can be used as textbook for graduate students by university teachers to prepare courses and seminars, and for active scientists and engineers who want to become familiar with a fascinating new field.

1. Introduction2. Triaxial testing under high confining pressures2.1. Triaxial testing2.2.1. Conventional apparatus2.2.2. Solid-medium Griggs type apparatus2.2.3. Cubic press2.2.4. Ultra-high pressure apparatus2.3. The method of triaxial testing in a cubic press2.3.1. Apparatus and sample assembly2.3.2. Experimental procedures at room temperature2.3.3. Experimental procedures at high temperaturesAppendix 2.1. Pressure scale Appendix 2.2. Observed examples of the effect of axial loading on confining pressure3. Experimemtal results on low porosity silicate rocks3.1. Compressive strength3.1.1. Pressure dependence of strength at moderate confining pressures3.1.2. Pressure dependence of strength at high confining pressures3.2. Acoustic emission3.3. Frictional strength under high confining pressures3.4. Fault features3.4.1. Sample preparation3.4.2. Features of faultingAppendix 3.1. Stress-strain curves at room temperatureAppendix 3.2. Strength data at room temperature4. Two types of brittle fracture4.1. High pressure type of fracture4.1.1. Comparison with previous high temperature experiments4.1.2. Transitional regime and semibrittle regime4.2. Other examples of two types of fracture4.2.1. Gneiss4.2.2. Experiments in a cubic press at high temperature 4.2.3. Temperature dependence of strength in the high-pressure type regime4.3. Micromechanics4.3.1. Introduction4.3.2. Micro-fracture styles4.3.3. Discussion on the mechanisms of fracturing4.3.4. SummaryAppendix 4.1. Strength data at elevated temperatures5. Geophysical and geological implications of the two types of fracture5.1. The conditions for application to the earth's interior5.2. The effect of size on rock strength under confining pressures5.2.1. The effect of size on uniaxial compressive strength and characteristic length5.2.2. The effect of size under confining pressure5.2.3. Implications in the earth's crust5.3. Strength of the lithosphere5.3.1. Brittle-ductile model5.3.2. A model including the high-pressure type fracture5.4. An approach to earthquake prediction research6. Mechanical behavior of porous silicate rocks6.1. Introduction6.2. Mechanical properties of a porous basalt under high confining pressure6.2.1. Volumetric strain6.2.2. AE activity6.2.3. Boundaries of mechanical states in the differential stress-confining pressure field6.3. Microstructural observations of porous basalt and the mechanism of cataclastic ductile flow6.3.1. Macroscopic observations6.3.2. Microscopic observations6.3.3. The mechanism of cataclastic ductile flow6.4. Change in the mechanism of cataclastic flow of porous rock under high confining pressure6.4.1. Creep analysis and equivalent viscosity6.4.2. Pressure-induced change in the mechanism of cataclastic flow6.5. High-pressure embrittlement6.5.1. High-pressure embrittlement in porous sandstone6.5.2. Microscopic observations of high-pressure embrittlement in eclogite6.5.3. Conditions and mechanism of high-pressure embrittlement 6.6. Structure of a fault zone and related geophysical and geological implicationsAppendix 6.1. Experimental data on the deformation of dry Yakuno basalt with 7% porosity at room temperatureAppendix 6.2. Characteristics of the cubic press with a large axial displacement