Engineering Rock Mechanics

248 Excavation principles

Civil

Engineering

“R

Objective: Creation of

Geometry specified

by engineering

function and location

with emphasis on

integrity of remaining

rock. Limited scope

for design.

Mining

Engineering

4, m

Petroleum

Engineering

r,

Objective: Obtaining

the excavated rock

Mine geometry

specified by orebody,

with emphasis on

excavated rock - but

many mining meth-

ods possible. Large

scope for design.

Objective:

Transporting oil

Borehole

cross-section dictated

by rotary drilling;

depth and orientation

I determined by oilfield

laccess and productioi

strategy. Limited

scope for design

Figure 15.1 The differing objectives of civil, mining and petroleum engineering.

internal geometry can be specified by mining engineers. Also, the design
life of different parts of a mine can vary from a few days (e.g. for a
temporary access) to a hundred years (for the main access). This leads to
many potential methods of excavating the rock in a mine, with different
methods being suited to different circumstances. Many elegant mining
methods have been developed, such as the ’longwall method’, which
consists essentially of a laterally moving tunnel. In a similar way, there
can be considerable design flexibility in the quantity and orientation of
wellbores used in petroleum engineering, but the remote access limits
the design scope.

t

100

% passing

(% below

size on

x-axis) block size distribution

0

0.001m3 1000 m3 lo6 m3

Figure 15.2 The process of rock excavation changes the pre-existing, natural, rock block

size distribution to the excavated fragment size distribution.