TY - JOUR
T1 - Geotribology - Friction, wear, and lubrication of faults
AU - Boneh, Yuval
AU - Reches, Ze'ev
N1 - Funding Information:
The present analysis was benefited from insightful discussions with Amir Sagy and Xiaofeng Chen. The authors acknowledge the thorough and constructive reviews by Takehiro Hirose and an anonymous reviewer. The work was supported, in part, by NSF Geophysics awards 1620330 and 1345087 and NEHRP award G13AP00048 to Ze'ev Reches, University of Oklahoma. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Government.
Publisher Copyright:
© 2017 Elsevier B.V.
PY - 2018/5/9
Y1 - 2018/5/9
N2 - We introduce here the concept of Geotribology as an approach to study friction, wear, and lubrication of geological systems. Methods of geotribology are applied here to characterize the friction and wear associated with slip along experimental faults composed of brittle rocks. The wear in these faults is dominated by brittle fracturing, plucking, scratching and fragmentation at asperities of all scales, including ‘effective asperities’ that develop and evolve during the slip. We derived a theoretical model for the rate of wear based on the observation that the dynamic strength of brittle materials is proportional to the product of load stress and loading period. In a slipping fault, the loading period of an asperity is inversely proportional to the slip velocity, and our derivations indicate that the wear-rate is proportional to the ratio of [shear-stress/slip-velocity]. By incorporating the rock hardness data into the model, we demonstrate that a single, universal function fits wear data of hundreds of experiments with granitic, carbonate and sandstone faults. In the next step, we demonstrate that the dynamic frictional strength of experimental faults is well explained in terms of the tribological parameter PV factor (= normal-stress · slip-velocity). This factor successfully delineates weakening and strengthening regimes of carbonate and granitic faults. Finally, our analysis revealed a puzzling observation that wear-rate and frictional strength have strikingly different dependencies on the loading conditions of normal-stress and slip-velocity; we discuss sources for this difference. We found that utilization of tribological tools in fault slip analyses leads to effective and insightful results.
AB - We introduce here the concept of Geotribology as an approach to study friction, wear, and lubrication of geological systems. Methods of geotribology are applied here to characterize the friction and wear associated with slip along experimental faults composed of brittle rocks. The wear in these faults is dominated by brittle fracturing, plucking, scratching and fragmentation at asperities of all scales, including ‘effective asperities’ that develop and evolve during the slip. We derived a theoretical model for the rate of wear based on the observation that the dynamic strength of brittle materials is proportional to the product of load stress and loading period. In a slipping fault, the loading period of an asperity is inversely proportional to the slip velocity, and our derivations indicate that the wear-rate is proportional to the ratio of [shear-stress/slip-velocity]. By incorporating the rock hardness data into the model, we demonstrate that a single, universal function fits wear data of hundreds of experiments with granitic, carbonate and sandstone faults. In the next step, we demonstrate that the dynamic frictional strength of experimental faults is well explained in terms of the tribological parameter PV factor (= normal-stress · slip-velocity). This factor successfully delineates weakening and strengthening regimes of carbonate and granitic faults. Finally, our analysis revealed a puzzling observation that wear-rate and frictional strength have strikingly different dependencies on the loading conditions of normal-stress and slip-velocity; we discuss sources for this difference. We found that utilization of tribological tools in fault slip analyses leads to effective and insightful results.
KW - Fault gouge
KW - Friction
KW - Geotribology
KW - Lubrication
KW - Wear
UR - http://www.scopus.com/inward/record.url?scp=85041620904&partnerID=8YFLogxK
U2 - 10.1016/j.tecto.2017.11.022
DO - 10.1016/j.tecto.2017.11.022
M3 - Review article
AN - SCOPUS:85041620904
VL - 733
SP - 171
EP - 181
JO - Tectonophysics
JF - Tectonophysics
SN - 0040-1951
ER -