Document Type

Article

Media Type

Text

Abstract

In bedded sedimentary or mechanically anisotropic rocks, joints often occur in laterally persistent, parallel sets with distinctive spacing attributes. Three of those attributes include a positively skewed distribution of joint spacings, a positive correlation between median spacing and mechanical layer thickness, and the tendency for rocks to appear saturated with joints and to show a ratio of layer thickness to median joint spacing near one. We identify total applied strain, mechanical interaction, joint propagation velocity, and flaws as key variables in the progressive jointing process, and we use a one-dimensional model of mechanically interacting joints to characterize the specific influence on joint spacing, of the number, sizes, and size distributions of flaws in rock. For a given flaw size distribution, the mode flaw size has no effect on spacing distribution shape, median spacing, or saturation. Layers with fewer flaws approach saturation more slowly and reach it with fewer joints and larger median joint spacing. The joint spacing distributions in these layers have variance and skewness that may be 1–3 orders of magnitude larger than in layers with greater numbers of flaws. Flaw size range affects the rate at which a jointing layer approaches saturation but not the number of joints at saturation. Resulting spacing distributions are similar, although narrow flaw size ranges tend to promote greater numbers of closely spaced joints. The skewness of a flaw size distribution affects the rate at which layers approach saturation, as well as the shape of the resulting joint spacing distribution at saturation. Negatively skewed flaw size distributions promote close joint spacing and create spacing distributions with greater variance and skewness.

DOI

10.1029/2005JB004115

Publication Date

7-1-2006

Comments

http://dx.doi.org/10.1017/S1352465811000300

Department

Department of Geology and Environmental Sciences

ISSN

0148-0227

Language

eng

Publisher

American Geophysical Union

Share

COinS
 
 

To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.