A laboratory study of the friction behavior of granular materials

I report on laboratory experiments designed to investigate the microphysical processes that result in rate- and state-dependent friction behavior and experiments designed to match the boundary conditions used by numerical models of granular friction. The effect of relative humidity (RH from <5% to 100%) is investigated with velocity stepping tests (10-20 tm/s) and slide-hold-slide (SHS) tests (3-1000 s) on 3 mm thick layers of quartz powder, alumina powder, Westerly granite powder, and Westerly granite blocks sheared at 25 MPa normal stress. Powders are conditioned in situ under controlled RH to create new surface area before shearing. A transition from velocity-strengthening to velocity-weakening frictional behavior occurs as RH increases. Frictional healing is negligible at low humidity and increases with increasing RH for both materials. While the coefficient of sliding friction for powders is independent of humidity, bare surface data indicate that sliding friction decreases with increased RH. Normal stress vibrations in SHS tests can add compaction induced granular strengthening, but for constant normal force tests, chemically assisted healing mechanisms control the friction behavior. The chemically assisted contact junction processes can be reduced or turned off at low humidity at room temperature in quartz and alumina. Velocity stepping tests and SHS tests are also performed at different values of applied normal stress (5 to 45 MPa) after pre-conditioning at high normal stress (40 and 35 MPa) for powders and no pre-conditioning for bare surfaces. Time-dependent frictional healing decreases with increasing normal stress.

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2002

Author dc:creator

• Frye, Kevin M. (Kevin Michael), 1972-

Advisor dc:contributor.advisor

• Chris Marone.

• Earth, Atmospheric, and Planetary Sciences.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/8013

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/8013