2001-12-11_PERMIT FILE - C1980007A ‎(2)‎

• Permit No: C1980007A
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Doc Name: By TOC Deleted
• Section_Exhibit Name: Exhibit 40 Geotechnical Analysis B & F Seams
• Media Type: D
• Archive: Yes

hlINID1G AP1D RECL.AMATIODI PLAfI April 1989
MT. CiJNNISON NO. 1 MINE
• T11e results of t1Le MINAP analysis are summarized in Tables
3.4.A.25 and 3.4.A.26 itt terms of offset barriers and distance
above seams where safety factors are 1.0 or less.
ROOF SUPPORT REQUIREMENTS
In mine development for both mining methods, and in room-and-
pillar extraction of the E and B Seams, roof support should be
generally accomplished with resin bolts and steel mats as in the
E Seam. However, in the longwall panels, additional and
different support will be needed. First, in the gate roads,
secondary support, additional to the primary resin bolts and
mats, will be required. This secondary support is needed to
protect the gate roads from the longwall abutment pressures.
Wooded posts, cribs, trusses, and combination bolts are commonly
used successfully itt western coal mines. Second, self advancing
powered supports will be needed to provide ground control at the
face.
The longwall face support must have suitable strength and
yielding characteristics to peep t}te immediate roof from breaking
at the coal face, while at the same time, they mast provide
adequate stiffness to cause the roof to break and 'cave
immediately behind. The function of the face supports is to }cold
• only a minor area of the roof; most of the roof pressure above
this area is taken by the solid coal face and surrounding
abutment zone in the gob and gate road pillars. Generally, the
faster the face advances, the better the working conditions
because there is less time allowed for "pressure points" to
develop. Itt selecting powered face support, the yield and
setting pYP.SSIIt'P.e (tht•ust to be provided against the roof and
floor) of they hydraulic legs have to be considered in relation
to the roof and Eloor strengths. Inadequate support yield and
setti.tLg pressures may permit excessive closure to occur at the
face and cause fractures to develop ahead and not behind the
supports. This condition can greatly hinder face operations.
Conversely, excessive setting loads in wealt rocks can cause the
support to pttnctttre the roof or floor. Generally, the conditions
itt the three seams at West Elk are expected to favor t}te use of
powered supports even though the F Seam floor may be weak in some
areas due to high clay content. The observed cave behavior in
the E' Seam seems well suited for longwall operations. The
indications are that this type of cave also s}tottld be expected in
t}Le E and B seams because wider panels (700 ft or more) favor
de•:•?lopment of a good cave in spite of }tigher depth and the
presence of slightly more satLdstones in the interburden of the
lower seams. T1Le :immediate roof seems to cave readily, tightly
and wit}t ltig}t bLtl.lting. This type of cave provides more support
for t}te upper beds and lower face support requirements than caves
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