APPCOR11673

• Permit No: C1981032
• IBM Index Class Name: Application Correspondence
• Doc Name: ROOF CONTROL DESIGN FOR 2ND EAST SECTION UNDER CURTIS CREEK VALLEY
• Media Type: D
• Archive: No

C
• W 20 t 4T = O.1D
-3-
where W width of the barrier pillar, T = thickness of pillar,
and D thickness of overburden. Therefore, with T = 10 ft
and D 480 ft.
W = 20 + 4(10) + 0.1(480) = 108 ft.~110 ft.
}yerex~s~&.ti~n,g.~..b~a+sn ire r p i'l l a r. i s -3 6 0 f e eft =w i.d-e , 3..,3.;. tyi;~,es;~t h,.,~'~
~d;~~o~f,,~;G:ht~:~~.c,_u..~a,ted~„barri,er•, .p~il,lar.r;e_qured.~
To date, Northern Coal Company has mined under
overburden in excess of 1,000 feet thick in the Rienau ll2 Mine,
using standard solid pillars of 80 feet by 60 feet on 100 feet
by 80 feet centers with no detectable convergence or pillar
failure. Also, both 1st and 2nd East Sections are Life of
Mine Entries. That is, these main entries will be maintained
for the life of the Rienau ll2 Mine for ventilation and haul-
age purposes. Therefore, there will be no retreat or second
mining in these entries.
Assuming worse case data, the following factors
have been determined:
(a) Entry pillars under the protected area
• have a factor of safety of 7.3.
(b) Entry pillars adjacent to the protected
area have a safety factor of 6.8.
(c) The Barrier Pillar between 1st and 2nd
East is 3 times larger than required.
(d) Virgin coal is adjacent to the northern
edge of the protected area.
(e) There will be no retreat or second mining
in 1st or 2nd East Sections.
(f) 1st and 2nd East Sections will be main-
tained for Life of Mine.
C'o~ns- •d:e s: i n.g , t hie a b uw e~fas~t~rys~i ,tom e ' a
yrrrl ..~
- T=e,d-tha;[.,p here. will_be no ?.stu.vb~am~e--.to.t.he,s ace
Oy e*L•`!.y.: ~:.,n.o_a,. _r-n~ , i ~.}1 Oi ~$6tae~d =~,.,.~ f a d _u e , t o. c o
~~.rgen~c:e,;ox:~.y- ^a r• Failure as mining advances. i
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