The White Pine news. [volume] (Ely, Nev.) 1906-1910, 1907-04-13
MINE rIMBERING.

Claude T. Rice of Bisbee has the
following on mine timbering In the
Engineering and Mining Journal:
Since the invention of the square
set little progress has been made IN
mine timbering. Indeed, it is such
an unapproachable subject as present
that timbering is considered mainly
q matter of judgment acquired after
long experience about mines. Min
ing men have devoted little effort to
the study of the subject.
Mr.. Storms has written a pamph-
let on mine timbering and frequent
articles describing the routine of the
timbering at different mines appear
in the mining periodicals, but little
has been written on the subject l
do not think one can figure on this
subject as a problem in pure mathe-
MATES, but | do believ that nature
has to great extent solved this
problem for us, and that If mining
men would make a systematic study
of the subject and its underlying
principles, data might be obtained to
give some notion of the support re-
CURED in underground workings.
Slopes cave until they assume a
selfsupporting arched or dome shape.
This small local dome remains COM
paratively unchanged in the the
writer opinion, as long as the froces
acting on the roof are those ude to
this stope alone. But as mining pro-
crosses. other slopes are opened up.
These affect one another One stope
caves, throwing upon the roof of
other slopes a sudden load, the elias
tic limit of the rock is passed, and
with it the nature of the force
changes No longer is it the simple
load of the simple stope which char
acterizes the scaling or caving stage,
but as the loads are suddenly thrown
upon the roof, the subsistence as
sumes a faulting nature.
This last stage is shown at Vir-
ginia City. New. where the FAULT
scrap, several feet in height, causing
by mining operations, outlines the
outcrop of the Comstock lode. The
same conditions may be observed at
The United Verde mine In oregon,
also TO a less extent at Butte, Mont
where from time to time there is n
cracking of walls in houses resting
on apparently solid ground. Ii is
this stage which is at present causing
trouble at Broken Hill In New Zea-
land, in which mining In the part
under The ocean had to be aban-
doned This stage has been the sub
ieot of some study by the colliery en-
gineers Of England and France, and
some data on it have been contrib
uted TO different societies
I believe that, except in few
cases of running ground so weak that
spiling is necessary. the theory Of
ground caving until 1t catches Itself
up Is all nonsense. I have been in
several caved slopes and have in all
Of them been able to worm my way
10 the top of the pile of caving,
where in every case a dome-like cav.
ity remained. | believe 1t Is always
there in the caving stage. for the fol-
lowing reason: In anything but run
ming ground large stope opening is
necessary before cavlng begins. and
this opening is SO large that the roof
assumes a self.supportlng arch shape
before the caving fills the stope. Be-
sides. the caying action is progress
i've, and when the caving begins to
MI the stope 1t so supports the walls
that caving ceases.
There are many circumstances
affecting the shape of the dome lip
the same rocks. such as joints. u.s.
lures and faults, as we'll as local va