2014-10-10_PERMIT FILE - C1996083 ‎(8)‎

• Permit No: C1996083
• IBM Index Class Name: Permit File
• Doc Date: 10/10/2014
• Section_Exhibit Name: Volume IIIA Exhibit 15 Subsidence Prediction
• Media Type: D
• Archive: No

2.4 BUILDING AND STRUCTURES
Criteria For Evaluating Impacts to Buildings and Structures
There are eight private buildings located within the Bowie #2 Mine permit area. The
potential impacts to structures are explained below.
Horizontal strain is a measure of the change in length of a piece of ground or
structure. Damage to surface structures is frequently a function of horizontal stains. Most
relevant codes specify maximum allowable horizontal strains in order to prevent damage to
various structures.
The complete strain profile at ground surface above an extraction area can be
developed using methods detailed in SEH. However, for the current study, it is considered
sufficient to estimate maximum strains, since the maximum damage to any structure which
could develop can be estimated from these values.
Strain is proportional to subsidence (S) and inversely proportional to depth (h), so
the maximum strain (E) over and excavation is proportional to S /h. Using the graph
presented in SEH, which is reproduced as Figure 15 -4, enables an estimate of maximum
strains. For a 860 foot wide panel, where the w/h ratio will be in excess of 1.0 at all
overburden depths of less than 860 feet, maximum compressive and tensile strains will be
on the order of 0.55 S/h and 0.65 S/h respectively. For a 9.5 foot mining height in both
seams, which is the most severe case which will exist at the Bowie #2 Mine, the following
maximum strains are predicted, assuming a maximum subsidence for double seam mining
from Figure 15 -3, for the profile which exists after the completion of mining two seams.
Overburden
W/h
Maximum Tensile
Maximum Compressive
Depth(Feet)
Stain (u- in /in)
Strain (u- in /in)
200
4.30
25842
20276
500
1.72
20501
16085
1,000
0.86
8038
7410
1,500
0.57
4330
6299
2,000
0.43
2362
4725
PR -14 -27- 06/14