COAL - Clpdigital.org

48 THE COAL TRADE BULLETIN.
cause, devise ways and means to terminate same
as soon as possible and prevent a recurrence. The
inspector peers patiently into every hole and
corner accompanied by tne mine foreman, a con­
scientious fellow that feels the condition of his
mine is stamping a never-to-be eradicated blot on
his managerial escutcheon. "Back along the
butts toward the main entries the room ribs were
mined out clean, I know that to be fact," says the
mine foreman, and the condition of the surface
indicates this. As this guarantees the safety of
the main entry all that can be done is to save the
material and attack chain pillars, ribs and stumps,
working them night and day to reduce the resist­
ance sufficiently and so produce another surface
break. This was done, effectually stopping the
trouble. Months after, a circuitous road was
driven ahead of the ruined part, sufficient barrier
was left, precluding the possibility of the creep
extending in that direction. The foreman is still
there. He has been reassured, the inspector has
proven to the satisfaction of all concerned, that,
had the foreman been the smartest mine manager
in existence he could not have prevented the dis­
aster. "His predecessor never had any trouble of
that nature." suggests some one. "No," said the
inspector, "because the system, up to the time of
his departure, was the proper one; at that time
it should have been altered, which the mine fore­
man had not the authority to do. The shaft, as
you remember, is situated in a vaney, the depth
to the coal being only 100 feet: the method of
mining was double entry, rooms 33 feet centers,
24 feet wide, leaving 9-foot ribs. Under the then
existing conditions this was barely sufficient to
steady the strata and allow the ribs to be drawn.
When this man took charge the entries were at
the point of entering under the surrounding hills,
which added from 400 to 600 feet of strata. Of
course, the method of running w-as not changed to
meet the altered surface conditions and before
the entries reached half way of their destination.
many of the rooms were worked out, nothing but
eoal veils left to resist the awful pressure of hills
nearly tall enough to reach the clouds. Natur­
ally, the ribs succumbed. The new style com­
pensates for all changes of surfaces that may
occur. The foreman was not culpable, but the
method or system was. There have been many
similar cases so it behooves us to look first to
the underground manager's environments before
condemning him for his seeming incompetency."
Previous to commencing development, all the
information concerning the territory, dip, nature
of roof, bottom, depth, etc, that it is possible to
obtain, should find an expression in the finally
adopted plan. This is an axiom among mining
engineers generally, but not always followed.
Often an engineer, to please his employer, will
indorse and incorporate suggestions from him
that he is convinced, by his knowledge of the nature
of the territory, should not be countenanced,
yet lacking the courage of his convictions they
become part and parcel of the scheme to the future
monetary loss of those he has patronized and the
detraction of his own character as an efficient
engineer. To a large number of operators any
scheme of mining that necessitates large ribs and
pillars is looked upon as wasteful and costly.
How much more so is one that proves inadequate.
bringing on a creep, burying beyond hope of re­
covery, thousands of tons of coal, not to mention
posts, rails, ties, etc.
The one all-important point to provide for in
room work is sufficient coal for room and rib to
ensure the stability of the working at all stages
of development. In the case cited above one
might ask, why were the rooms not cut down to
21 feet? This would not have prevented the
crash, as 12 feet of rib was not enough. A com­
mon fault of many systems of mining is their
inflexibility, no opportunity is given the superin­
tendent or foreman to exercise his judgment.
Take 33-foot room centers; in a shallow-covered
coal it will answer, but, how foolish to insist that
it is just the thing for all depths as some do.
Should the workings underlie the surface 300 to
600 feet the inevitable result follows, a creep.
Superintendent and foreman see it coming; they
are powerless; to drive rooms less than 21 feet
means a battle with the miners, this is a very
effectual barricade in that direction and the en­
gineer has just as effectually blocked him in the
other.
Let your superintendents have a little swing;
give them a plan pliable in its nature, something
they can bend to fit irregularities, say, 39 foot
centers; on your maps place contours of the sur­
face; say to him, here is a part of our property
where you will have only 100 feet of surface, try
and drive your rooms about 27 feet wide here,
leaving a 12-foot rib. now here are about 250
acres where the depth to the coal increases 300
feet, rooms should je 24 feet wide, ribs 15 feet.
Further over toward the boundary line you will
observe the contours show 400 to 600 feet; rooms
must not be more than 21 feet providing 18-foot
ribs. All these changes can be effected without
change of track or partings. Thus, under nearly
all surface conditions to be met with, generally
speaking, creeps can be prevented. This advice
was given by the inspector in the case cited and
it was adopted. 'this was nearly two years ago
and we have not heard of any creeps since. At
the same time chain pillars were increased from
30 to 45 feet to allow of machine room to be
driven up the center when the entries stumps are
being cleaned out. Besides no rooms are turned
nearer than 150 to 200 feet to the main entries.
(To BE CONTINUED).