This paper reviews an analytical model that defines the relationship of
weight-weighted or volume-weighted average haulage distance with
bench height and other related parameters; presents the optimum bench
heights under various conditions in terms of minimising the weighted
average haulage distance of ore/waste during the full lifetime of an open
pit mine, and discusses the truck-haulage economics of mining open pits
by high bench, specifically by 15 m, 18 m and 20 m bench through
marginal analysis. The observations from these analyses disprove the
previous conflicting assertions that the overall weighted average haulage
distance either increases or decreases monotonically with bench height. It
is concluded that: (i) an increase of bench height to 15 m from 12 m is
likely to be viable under the general conditions of large-scale deep
open-pit mines; (ii) the reduction of haulage cost is limited with the case
of increasing bench height to 18 m from 15 m; and (iii) the feasibility of
mining open pits by 20 m benches is generally questionable. These
conclusions may serve as a useful guide for those who advocate open pit
mining by high benches.