Friction on a granite to granite interface

Lajtai, E.Z.; Gadi, A M

doi:10.1007/bf01274118

Cited by 18 publications

(7 citation statements)

References 13 publications

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“…Consequently, it is difficult to draw a definitive conclusion about Wong and Zhao's [1990] data on the velocity dependence of the "static" friction coefficient. Other published studies Teufel and Logan, 1978;Shimamoto and Logan, 1986;Lajtai and Gadi, 1989] have confirmed that the "static" coefficient increased with decreasing load point velocity, in agreement with our numerical simulation results. However, it should be emphasized that as far as the data in Figure 13a and 13b concerned, the stress drop amplitude and its variation with load point velocity were so large that our interpretation should not be biased by the second-order effects from the jacket.…”

Section: Point (B Insupporting

confidence: 92%

Effects of loading velocity, stiffness, and inertia on the dynamics of a single degree of freedom Spring‐Slider System

Gu¹,

Wong²

1991

J. Geophys. Res.

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Numerical simulation of the nonlinear dynamics of a single degree of freedom spring‐slider system can provide useful insight into the effects of loading velocity, friction environment, elastic stiffness, and inertia on the stress drop and dynamic behavior of earthquakes. In our numerical simulations using a rate‐ and state‐dependent friction law, we varied the loading velocity by 7 orders of magnitude, the stiffness by 2 orders of magnitude, the mass by 5 orders of magnitude, and the velocity‐weakening parameter (B‐A) by a factor of 160. Four stability regimes were identified in the load point velocity‐stiffness space when inertia was taken into account. For cyclic stick‐slip instabilities, the stress drop amplitude increases with decreasing load point velocity, with decreasing stiffness, with increasing velocity weakening parameter B‐A, and with decreasing mass. Simple scaling relations for the static stress drop, dynamic stress drop, “static” friction, and shear fracture energy with the natural logarithm of load point velocity were observed. Using the scaling relation for static stress drop, we infer the normalized velocity weakening parameter b‐a (with respect to normal stress) to range from 0.0011 to 0.0039 for triaxial experiments on saw cut Westerly granite specimens sandwiched with a simulated gouge layer of ultrafine quartz at pressures from 10 MPa to 100 MPa. Unless we take b‐a throughout the seismogenic layer to be much higher than experimental measurements, the effect of loading velocity by itself is not sufficient to account for the increase of stress drop with increasing earthquake recurrence time inferred from seismological data. To the extent that our simple system can be treated as an analog for earthquakes, our study shows that the velocity weakening parameter (B‐A) controls the magnitude of the static stress drop far more than the loading velocity. If velocity weakening increases systematically with increasing healing time, then the coupled effect of loading velocity variation and change in friction environment can account for the seismological observations.

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Section: Point (B Insupporting

confidence: 92%

Effects of loading velocity, stiffness, and inertia on the dynamics of a single degree of freedom Spring‐Slider System

Gu¹,

Wong²

1991

J. Geophys. Res.

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“…The block was bounded by three steeply dipping fracture surfaces, and rested on a 17 to 27 m wide ledge with downslope dip of 46°. Assuming a static friction angle for unpolished granite of between 42° and 51° (Goodman, ; Lajtai and Gadi, ) and that joint cohesion was minimal dictates that the detached block was, at best, metastable with respect to sliding. However, the fractures bounding the back of the failed rock mass and which formed the detachment surface are inclined at 67° and 90° obliquely to and away from the cliff face, and thus, the center of mass was well‐within the bottom footprint of the block (Figure C), providing resistance to overturning moments.…”

Section: Resultsmentioning

confidence: 99%

Rock fall dynamics and deposition: an integrated analysis of the 2009 Ahwiyah Point rock fall, Yosemite National Park, USA

Zimmer

Collins

Stock

et al. 2012

Earth Surf Processes Landf

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We analyzed a combination of airborne and terrestrial LiDAR, high‐resolution photography, seismic, and acoustic data in order to gain insights into the initiation, dynamics, and talus deposition of a complex rock fall. A large (46 700 m3) rock fall originated from near Ahwiyah Point in eastern Yosemite Valley and fell a total of 730 m to the valley floor on 28 March 2009. Analyses of remote sensing, seismic, and acoustic data were integrated to reconstruct the rock fall, which consisted of (1) the triggering of a 25 400 m3 rock block in an area of intersecting and sometimes highly weathered joint planes, (2) the sliding and subsequent ballistic trajectory of the block from a steeply dipping ledge, (3) dislodging of additional rock from the cliff surface from beneath the rock fall source area, (4) a mid‐cliff ledge impact that detached a volume of rock nearly equivalent in volume to the initial block, (5) sliding of the deteriorating rock mass down the remainder of the cliff, and (6) final impact at the base of the cliff that remobilized the existing talus downward and outward and produced an airblast that knocked down hundreds of trees. The depositional geomorphology indicates that the porosity of the fresh talus is significantly lower than that expected for typical blocky talus slopes, likely because the rock debris from this event was pulverized into smaller, more poorly sorted fragments and densified via dynamic compaction when compared to less energetic, fragmental‐type rock falls. These results suggest that accumulation of individual rock‐fall boulders tends to steepen talus slopes, whereas large, energetic rock falls tend to flatten them. Detachment and impact signals were recorded by seismic and acoustic instruments and highlight the potential use of this type of instrumentation for generalized rock fall monitoring, while LiDAR and photography data were able to quantify the cliff geometry, rock fall volume, source and impact locations, and geomorphological changes to the cliff and talus. Published in 2012. This article is a US Government work and is in the public domain in the USA.

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“…Our 2D geometric model considers a plane strain with a thickness far less than the height and width dimensions. The parameters related to granite failure in Equation are derived from Lajtai and Gadi (1989), and the failure equation can be expressed as

ψ = ((), ((), σ_{3} + C 1 * normalΔ p_{(normalt)}) - normalQ * ((), σ_{1} + C 1 * normalΔ p_{(normalt)}) + normalN * ((), 1 + ((), σ_{2} - σ_{1}) / ((), σ_{3} - σ_{1})) / normalC 2),

Q = ((), ((), 1 + sin θ) / 1 + sin θ),

N = ((), ((), 2 cos θ) / ((), 1 - sin θ)) S_{o},

where, σ 1 , σ 2 , and σ 3 are the principal stresses, Pa. It should be noted that the principal stresses are calculated within the model and updated continuously during the simulation.…”

Section: Failure Parametersmentioning

confidence: 99%

“…Our 2D geometric model considers a plane strain with a thickness far less than the height and width dimensions. The parameters related to granite failure in Equation 24 are derived from Lajtai and Gadi (1989), 55 and the failure equation can be expressed as 53…”

Section: Failure Parametersmentioning

confidence: 99%

Multifracture response to supercritical CO ₂ ‐EGS and water‐EGS based on thermo‐hydro‐mechanical coupling method

et al. 2019

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Summary Hydraulic‐fracturing treatments have become an essential technology for the development of deep hot dry rocks (HDRs). The deep rock formation often contains natural fractures (NFs) at micro and macroscales. In the presence of the NF, the hydraulic‐fracturing process may form a complex fracture network caused by the interaction between hydraulic fractures and NF. In this study, analysis of carbon dioxide (CO2)‐based enhanced geothermal system (EGS) and water‐based EGS in complex fracture network was performed based on the thermo‐hydro‐mechanical (THM) coupling method, with various rock constitutive models. The complexity of the fracture geometry influences the fluid flow path and heat transfer efficiency of the thermal reservoir. Compared with CO2‐based EGS, water‐based EGS had an earlier thermal breakthrough with a rapid decline in production temperature. CO2 can easily gain heat rising its temperature thus reducing the effect of a premature thermal breakthrough. Both CO2‐based EGS and water‐based EGS are affected by in‐situ stress; the increase in stress ratio improved the fracture permeability but resulted in an early cold thermal breakthrough. When the same injection rate is applied to water‐based EGS and CO2‐based EGS, water‐based EGS displayed higher injection pressure buildup. Water‐based EGS had higher reservoir deformation area than CO2‐based EGS, and thermoelastic constitutive model for water‐based EGS showed larger deformed area ratio than thermo‐poroelastic rock model. Furthermore, higher values of rock modulus accelerated the reservoir deformation for water‐based EGS. This study established a novel discussion investigating the performance of CO2‐based EGS and water‐based EGS in a complex fractured reservoir. The findings from this study will help in deepening the understanding of the mechanisms involved when using CO2 or water as a working fluid in EGS.

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Friction on a granite to granite interface

Cited by 18 publications

References 13 publications

Effects of loading velocity, stiffness, and inertia on the dynamics of a single degree of freedom Spring‐Slider System

Effects of loading velocity, stiffness, and inertia on the dynamics of a single degree of freedom Spring‐Slider System

Rock fall dynamics and deposition: an integrated analysis of the 2009 Ahwiyah Point rock fall, Yosemite National Park, USA

Multifracture response to supercritical CO ₂ ‐EGS and water‐EGS based on thermo‐hydro‐mechanical coupling method

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Friction on a granite to granite interface

Cited by 18 publications

References 13 publications

Effects of loading velocity, stiffness, and inertia on the dynamics of a single degree of freedom Spring‐Slider System

Effects of loading velocity, stiffness, and inertia on the dynamics of a single degree of freedom Spring‐Slider System

Rock fall dynamics and deposition: an integrated analysis of the 2009 Ahwiyah Point rock fall, Yosemite National Park, USA

Multifracture response to supercritical CO 2 ‐EGS and water‐EGS based on thermo‐hydro‐mechanical coupling method

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Multifracture response to supercritical CO ₂ ‐EGS and water‐EGS based on thermo‐hydro‐mechanical coupling method