508L5.9.2.07 - Mechanics of Earthquakes and Faulting 9 Feb....

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Mechanics of Earthquakes and Faulting Mechanics of Earthquakes and Faulting Dilatancy Hardening and Stability Mead, 1925 (Mead, W. J., The geologic role of dilatancy. Jour. Geol. 33, 685-698, 1925.) Volumetric work and stability. Frank, 1965 (Frank, F. C., On dilatancy in relation to seismic sources. Rev. Geophys. 3, 485-503, 1965) Rock Friction Granular Friction Wear and Gouge Formation Stick Slip Stability 9 Feb. 2007
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dh dx Work of frictional shear with volume change W is total work of shearing per unit volume W = τ d γ = σ μ d dq = dV / V ; dg = dx / h µ = µ p + dh/dx Dilatancy rate is a key factor for bulk frictional strength
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Mead, 1925 (Geologic Role of Dilatancy) Shear Localization Marone, 1998 Strain homogeneity depends on whether dilatancy is restricted Homogeneous strain if dilatancy is not opposed Strain localization if deformed under finite confining pressure Shear Bands Form if:
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Mead, 1925 (Geologic Role of Dilatancy) Shear Localization Strain homogeneity depends on whether dilatancy is restricted Homogeneous strain if dilatancy is not opposed Strain localization if deformed under finite confining pressure Shear Bands Form if: τ = s m p + dq / dg ( ) W = t p dg + s dq Shear strength depends on friction and dilatancy rate Deformation mode (degree of strain localization) minimizes dilatancy rate
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Mead, 1925 (Geologic Role of Dilatancy) Shear Localization Strain homogeneity depends on whether dilatancy is restricted Homogeneous strain if dilatancy is not opposed Strain localization if deformed under finite confining pressure Shear Bands Form if: τ = s m p + dq / dg ( ) W = t p dg + s dq Shear strength depends on friction and dilatancy rate Deformation mode (degree of strain localization) minimizes dilatancy rate
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Frank, 1965. Volumetric work, shear localization and stability. Applies to Friction and Fracture Volume Strain, θ Shear Strain, γ Strain hardening when: Strain softening when:
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Volume Strain, θ Shear Strain, γ Marone, Raleigh & Scholz, 1990
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Volume Strain, θ Shear Strain, γ Marone, Raleigh & Scholz, 1990
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Basic friction theory Amonton’s laws Chemical effects Hydrolytic weakening Basic observations of: time-dependent static friction velocity-dependent sliding friction Adhesive theory of friction Hertian contact ploughing Friction
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Base Friction vs. 2nd order variations
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508L5.9.2.07 - Mechanics of Earthquakes and Faulting 9 Feb....

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