Abstract
Triaxial compression experiments were performed on samples of natural granular fault gouge from the Lopez Fault in Southern California. This material consists primarily of quartz and has a self-similar grain size distribution thought to result from natural cataclasis. The experiments were performed at a constant mean effective stress of 150 MPa, to expose the volumetric strains associated with shear failure. The failure strength is parameterized by the coefficient of internal friction μ, based on the Mohr-Coulomb failure criterion.
Samples of remoulded Lopez gouge have internal friction μ=0.6±0.02. In experiments where the ends of the sample are constrained to remain axially aligned, suppressing strain localisation, the sample compacts before failure and dilates persistently after failure. In experiments where one end of the sample is free to move laterally, the strain localises to a single oblique fault at around the point of failure; some dilation occurs but does not persist. A comparison of these experiments suggests that dilation is confined to the region of shear localisation in a sample. Overconsolidated samples have slightly larger failure strengths than normally consolidated samples, and smaller axial strains are required to cause failure. A large amount of dilation occurs after failure in heavily overconsolidated samples, suggesting that dilation is occurring throughout the sample. Undisturbed samples of Lopez gouge, cored from the outcrop, have internal friction in the range μ=0.4–0.6; the upper end of this range corresponds to the value established for remoulded Lopez gouge. Some kind of natural heterogeneity within the undisturbed samples is probably responsible for their low, variable strength. In samples of simulated gouge, with a more uniform grain size, active cataclasis during axial loading leads to large amounts of compaction. Larger axial strains are required to cause failure in simulated gouge, but the failure strength is similar to that of natural Lopez gouge.
Use of the Mohr-Coulomb failure criterion to interpret the results from this study, and other recent studies on intact rock and granular gouge, leads to values of μ that depend on the loading configuration and the intact or granular state of the sample. Conceptual models are advanced to account for these descrepancies. The consequences for strain-weakening of natural faults are also discussed.
Similar content being viewed by others
References
Amadei, B., andRobinson, M. J.,Strength of rock in multiaxial loading conditions. InProc. 27th U.S. Symp. on Rock Mechanics (University of Alabama 1986) pp. 47–55.
Biegel, R. L., Sammis, C. G., andDieterich, J. H. (1989),The Frictional Properties of a Simula Gouge Having a Fractal Particle Distribution, J. Struct. Geol.11, 827–846.
Byerlee, J. D., andSavage, J. C. (1993),Coulomb Plasticity within the Fault Zone, Geophys. Res. Lett.19, 2341–2344.
Byerlee, J. D. (1978),Friction of Rocks, Pure Appl. Geophys.116, 615–626.
Chester, F. M., andLogan, J. M. (1987),Composite Planar Fabric of Gouge from the Punchbowl Fault, California, J. Struct. Geol.9, 621–634.
Chester, F. M., andLogan, J. M. (1986),Implications for Mechanical Properties of Brittle Faults from Observations of the Punchbowl Fault Zone, California, Pure Appl. Geophys.124, 79–106.
Fredrich, J. T., andEvans, B.,Strength recovery along simulated faults by solution transfer processes. In33rd U.S. Rock Mechanics Symposium (eds. Tillerson, J. R., and Wawersik, W. R.) (Balkema, A. A., Rotterdam 1969) pp. 121–130.
Green, G. E., andBishop, A. W. (1969),A Note on the Drained Strength of Sand under Generalized Strain Conditions, Geotechnique19, 144–149.
Hansen, B.,Shear box tests on sand. InProc. 5th Int. conf. on Soil Mech. and Found. Eng. (ed. Dunod, Paris 1969) pp. 127–131.
Hobbs, B. E., Ord, A., andMarone, C.,Dynamic behavior of rock joints. InProc. Int. Symp. on Rock Joints (eds. Barton, N. R., and Stephansson, O.) (Loen, Norway 1990) pp. 435–445.
Jones, L. M. (1981),Field and Laboratory Studies of the Mechanics of Faulting, Ph.D. Thesis, Massachusetts Institute of Technology, 106 pp.
Jones, L. M. (1980),Cyclic Loading of Simulated Gouge to Large Strains, J. Geophys. Res.85, 1826–1832.
Lockner, D. A., andByerlee, J. D. (1993),How Geometric Constraints Contribute to the Weakness of Mature Faults, Nature363, 250–252.
Mandl, G.,Mechanics of Tectonic Faulting (Elsevier, Amsterdam 1988) 407 pp.
Mandl, G., de Jong, L. N. J., andMaltha, A. (1977),Shear Zones in Granular Material, Rock Mechanics9, 95–144.
Marone, C., andKilgore, B. (1993),Scating of the Critical Slip Distance for Seismic Faulting with Shear Strain in Fault Zones, Nature362, 618–621.
Marone, C., Hobbs, B. E., andOrd, A. (1992),Coulomb Constitutive Laws for Friction: Contrasts in Frictional Behavior for Distributed and Localized Shear, Pure Appl. Geophys.139, 195–214.
Marone, C., andScholz, C. H. (1989),Particle-size Distribution and Microstructures within Simulated Fault Gouge, J. Struct. Geol.11, 799–814.
Mogi, K. (1967),Effect of Intermediate Principal Stress on Rock Failure, J. Geophys. Res.72, 5117–5131.
Oakeshott, G. B. (1958),Geology and Mineral Deposits of San Fernando Quadrangle, Los Angeles County, California, Calif. Div. Mines Bull.172, 147 pp.
Rice, J. R. (1979),Theory of Precursory Processes in the Inception of Earthquake Rupture, Gerlands Beitr. Geophysik88, 91–127.
Rice, J. R.,Fault stress states, pore pressure distribution, and the weakness of the San Andreas Fault. InFault Mechanics and Transport Properties of Rocks (eds. Evans, B., and Wong, T.-F.) (Academic Press, 1992) pp. 475–503.
Sammis, C. G., King, G. C. P., andBiegel, R. L. (1987),The Kinematics of Gouge Deformation, Pure Appl. Geophys.125, 777–812.
Sammis, C. G., andBiegel, R. L. (1989),Fractals, Fault-gouge, and Friction, Pure Appl. Geophys.131, 255–271.
Scott, D. R., Marone, C., andSammis, C. G. (1994),The Apparent Friction of Granular Fault Gouge in Sheared Layers, J. Geophys. Res., in press.
Stuart, W. D. (1979),Strain Softening Prior to Two-dimensional Strike Slip Earthquakes, J. Geophys. Res.84, 1063–1070.
Takahashi, M., andKoide, H.,Effect of the intermediate principal stress on strength and deformation behavior of sedimentary rocks at depth shallower than 2000 m. InRock at Great Depth (eds. Maury and Fourmaintraux) (Balkema, Rotterdam 1992) pp. 19–26.
Yamamuro, J. A., andLade, P. V. (1993),Instability and Behavior of Granular Materials at High Pressures, Report No. UCLA-ENG-93-26, Civil Engineering Department, University of California, Los Angeles.
Zoback, M. D., andByerlee, J. D. (1976a),A Note on the Deformational Behavior and Permeability of Crushed Granite, Int. J. Rock Mech. Min. Sci. and Geomech. Abstr.13, 291–294.
Zoback, M. D., andByerlee, J. D. (1976b),Effect of High-pressure Deformation on the Permeability of Ottawa Sand, AAPG Bull.60, 1531–1542.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Scott, D.R., Lockner, D.A., Byerlee, J.D. et al. Triaxial testing of Lopez Fault gouge at 150 MPa mean effective stress. PAGEOPH 142, 749–775 (1994). https://doi.org/10.1007/BF00876063
Received:
Revised:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00876063