What can granular media teach us about deformation in geothermal systems

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Experiments on granular media have significantly improved our understanding of deformation processes in porous rocks. Laboratory results have lead to fundamental theoretical developments (such as poroelasticity, or rate and state-variable friction) that have found widespread application. This paper presents results from laboratory experiments that help constrain these theories. Data from triaxial deformation experiments on quartz sand aggregates are used to illustrate stress-dependent behavior of poroelastic parameters (e.g. the Biot-Willis and Skempton coefficients). Calculations for these coefficients show systematic variations as effective stress increases, in a manner consistent with measured compressibilities of the aggregate. Data from shear experiments show that frictional ... continued below

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Karner, Stephen L. June 1, 2004.

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Experiments on granular media have significantly improved our understanding of deformation processes in porous rocks. Laboratory results have lead to fundamental theoretical developments (such as poroelasticity, or rate and state-variable friction) that have found widespread application. This paper presents results from laboratory experiments that help constrain these theories. Data from triaxial deformation experiments on quartz sand aggregates are used to illustrate stress-dependent behavior of poroelastic parameters (e.g. the Biot-Willis and Skempton coefficients). Calculations for these coefficients show systematic variations as effective stress increases, in a manner consistent with measured compressibilities of the aggregate. Data from shear experiments show that frictional strength varies systematically with time and temperature. At temperatures below 450 oC, shear zones exhibit greater cohesive strengths as the time of stationary contact increases (hence, positive healing rates). For conditions exceeding 450 oC, shear zone strength is seen to decrease with contact time (negative healing rates). The results from both volumetric compaction and frictional shear experiments are well described by poroelasticity as well as rate and state-variable friction. The combination of these constitutive relations may provide a powerful tool that can be used in numerical models that couple thermal, mechanical, hydraulic, and temporal processes – as occur in geothermal systems.

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  • 40th U.S. Rock Mechanics Symposium (ALASKA ROCKS 2005),Anchorae, Alaska,06/25/2005,06/29/2005

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  • Report No.: INEEL/CON-04-02498
  • Grant Number: DE-AC07-99ID-13727
  • Office of Scientific & Technical Information Report Number: 911114
  • Archival Resource Key: ark:/67531/metadc888432

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  • June 1, 2004

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  • Sept. 22, 2016, 2:13 a.m.

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  • Dec. 15, 2016, 3:04 p.m.

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Karner, Stephen L. What can granular media teach us about deformation in geothermal systems, article, June 1, 2004; [Idaho Falls, Idaho]. (digital.library.unt.edu/ark:/67531/metadc888432/: accessed December 11, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.