LUESTION $4-$ Stope Support Elements

A Mine exploiting UG$2$ in tabular excavation stoping uses timber elongates and yield pillars

as primary support in the UG$2$ stope panels. The timber elongates are installed $1\mathrm{.}5$ m on

dip and $2\mathrm{.}0$ m on strike centre to centre. The information available to you includes the

following:

Depth of mining below surface $=150$

Stoping width $=1\mathrm{.}2m$

Rock density $=3200k\frac{g}{m^3}$

K$-$ratio $=0\mathrm{.}95$

Excavation half span $=80m$

The Poisson's ratio $=0\mathrm{.}25$

The Young's modulus $=98$GPa

The reef orebody dips at $18$

The fall out height in UG$2$ stopes $=0\mathrm{.}7m$

$4\mathrm{.}1$ Assuming a gravitational constant of $10\frac{m}{s^2},$ calculate the required support

resistance $($demand$)$ in the stope.

$4\mathrm{.}2$ If the timber elongate is installed to support a brow in a stope $4$ m behind the face,

calculate elastic closure that the timber elongate would undergo if the face is

advanced for $15$ m $.$

$4\mathrm{.}3$ Calculate the elastic closure rate in $m\frac{m}{m}$ after the face is advanced for $15$ m $.$

$4\mathrm{.}4$ Since the face advanced $15$ m $,$ you noticed a bed separation of $3$ cm on the brow

supported by the timber elongate. Calculate the new stoping width where the timber

elongate is installed.

$4\mathrm{.}5$ Draw the load$-$deformation curves of the grout pack, pre$-$stressed timber pack.

elongate prog and hydraulic prop, all together on a single graph paper.

$4\mathrm{.}6$ Which of the drawn support types will have high initial stiffness.

$4\mathrm{.}7$ Which of the drawn support types will be prestressed.

$4\mathrm{.}8.$ Which of the drawn support types will provide large peak strength at low rates of

closure?

$4\mathrm{.}9.$ Which of the drawn support types will provide large peak strength at high rates of

closure?

$4\mathrm{.}10$ With the aid of an annotated diagram, describe the effect of loading rate on the

performance of timber support units when comparing the load $/$ deformation

characteristics determined in laboratory tests to the performance under i$)$ quasi$-$

static $($rock fall$)$ and ii$)$ dynamic $($rock burst$)$ conditions.