My WebLink
|
Help
|
About
|
Sign Out
Home
Browse
Search
2017-08-31_REPORT - C1980007
DRMS
>
Day Forward
>
Report
>
Coal
>
C1980007
>
2017-08-31_REPORT - C1980007
Metadata
Thumbnails
Annotations
Entry Properties
Last modified
9/1/2017 9:26:06 AM
Creation date
9/1/2017 8:57:21 AM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
C1980007
IBM Index Class Name
Report
Doc Date
8/31/2017
Doc Name
Subsidence Monitoring Report
From
Wright Water Engineers, Inc
To
DRMS
Annual Report Year
2017
Permit Index Doc Type
Subsidence Report
Email Name
LDS
JRS
Media Type
D
Archive
No
There are no annotations on this page.
Document management portal powered by Laserfiche WebLink 9 © 1998-2015
Laserfiche.
All rights reserved.
/
62
PDF
Print
Pages to print
Enter page numbers and/or page ranges separated by commas. For example, 1,3,5-12.
After downloading, print the document using a PDF reader (e.g. Adobe Reader).
View images
View plain text
Spring 2015 Subsidence and Geologic Field Observations <br />South of Divide and Dry Fork Mining Areas <br />5.0 CONCLUSIONS <br />1. The conceptual B- and E -seam mining model presented in the Exhibit 60 series of the <br />mining permit has been verified by annual field observations in the West Elk Mine area. <br />Under the longwall mining methods and related uniform downwarping of the overburden <br />rocks and unconsolidated material as laterally constrained plates, cracks in zones under <br />tensile stress narrow with depth, and close at the neutral surface. Below the neutral surface, <br />the materials are therefore in compression. This has an important bearing on the hydrologic <br />consequences of longwall mining. Any groundwater or surface water in contact with a <br />given subsidence crack is prevented from traveling downward beyond the neutral surface <br />of the deformed plate. Annual field observations from 1996 to spring 2017 (inclusive), <br />verify this conceptual model in bedrock and surficial material (colluvium, alluvium, <br />mudflow, and debris flow deposits) where the overburden is laterally constrained. <br />2. Typically, uniform downwarping occurs in association with longwall mining when there <br />is lateral constraint. Where there are steep slopes and cliffs, there is little to no lateral <br />support in at least one direction, which causes the associated rocks and unconsolidated <br />materials to deform as unconstrained beams, plates or cantilevers as the longwall mining <br />faces move beneath them. This lack of lateral constraint allows subsidence cracks to <br />commonly extend completely through sandstones and other brittle units and groundwater <br />or surface water present near or within these cracks will likely flow through and exit into <br />existing surface drainages. The relatively few cliffs and over -steepened slopes in the SOD <br />and Dry Fork mining areas tend to provide the lateral constraint needed to produce a more <br />uniform down -warping with fewer significant subsidence cracks observable at the surface. <br />3. To date, there have been no observed or reported water losses associated with the longwall <br />mining activities. <br />4. Continuous annual observations find substantial weathering of previously -observed <br />subsidence cracks with edges rounding, widths reducing, and depths filling with eroded <br />material. The only exception to these observations has been those cracks in thick, exposed, <br />831-032.798 Wright Water Engineers, Inc. Page 27 <br />August 2017 <br />
The URL can be used to link to this page
Your browser does not support the video tag.