Advanced Search
Select up to three search categories and corresponding keywords using the fields to the right. Refer to the Help section for more detailed instructions.

Search our Collections & Repository

All these words:

For very narrow results

This exact word or phrase:

When looking for a specific result

Any of these words:

Best used for discovery & interchangable words

None of these words:

Recommended to be used in conjunction with other fields

Language:

Dates

Publication Date Range:

to

Document Data

Title:

Document Type:

Library

Collection:

Series:

People

Author:

Help
Clear All

Query Builder

Query box

Help
Clear All

For additional assistance using the Custom Query please check out our Help Page

Filetype[PDF-1.01 MB]


  • English
    • Details You May Also Like

    Details:

    • Personal Author:
    • Corporate Authors:
      United States. Bureau of Mines.
    • Description:
      "The natural vertical fracture system in bituminous coalbeds is called cleat. Cleat orientation commonly controls the direction of mining with major development paralleling the face cleat. Previous researchers have categorized the origin of cleat as endogenetic, relating the origin of cleat to compaction and coalification, and exogenetic, relating the origin of cleat to tectonic forces. In the coalbeds studied for this report it was found that tectonic forces were the controlling factor of cleat formation. Face cleats were formed as extension fractures during structural deformation, and butt cleats, as release fractures during erosion and uplift. The face cleat of the Pittsburgh coalbed rotates from n 80 deg w in northwestern West Virginia to n 57 deg w in southwestern Pennsylvania; the face cleat maintains a perpendicular orientation to the shifting axial trend of local structures. Cleat orientation in other bituminous coalbeds in Virginia, Utah, Oklahoma, and central Pennsylvania showed a similar relationship to local structure. Directional permeability of coal is directly related to cleat. Holes drilled perpendicular to the face cleat yield from 2.5 to 10 times the amount of gas released as compared with holes drilled perpendicular to the butt cleat." - NIOSHTIC-2

      NIOSHTIC no. 10000624

    • Subjects:
    • Series:
      Report of investigations (United States. Bureau of Mines) ; 7910
    • Document Type:
      Report
    • Collection(s):
    • Main Document Checksum:
    • Download URL:
    • File Type:

    Supporting Files

    • No Additional Files

    More +

    You May Also Like

    Checkout today's featured content at stacks.cdc.gov