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Frictional strength of cuttings and core from SAFOD drillhole phases 1 and 2

Geophysical Research Letters

By:
, , , , ,
DOI: 10.1029/2006GL027626

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Abstract

We investigated the frictional properties of drill cuttings and core obtained from 1.85-3.1 km true vertical depth in the SAFOD scientific borehole in central California. Triaxial frictional sliding experiments were conducted on samples from primary lithologic traits and significant shear zones, including the inferred active trace of the San Andreas fault. The samples were deformed at room temperature under constant effective normal stresses of 10, 40, and 80 MPa with axial shortening rates of 0.01-1.0 ??m s-1. The weakest samples were from shale, claystone, and siltstone units with friction coefficient ?? = 0.4-0.55. Stronger samples were from quartzo-feldspathic rocks with ?? ??? 0.6. Materials tested from two shear, zones at 2560 and 3067 m measured depth had ?? = 0.4-0.55 and velocity strengthening behavior consistent with fault creep at depths <4 km. The coefficient of friction for bulk samples from the inferred trace of the San Andreas fault was ???0.6. Copyright 2006 by the American Geophysical Union.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Frictional strength of cuttings and core from SAFOD drillhole phases 1 and 2
Series title:
Geophysical Research Letters
DOI:
10.1029/2006GL027626
Volume
33
Issue:
23
Year Published:
2006
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Geophysical Research Letters