There are many parameters that govern the generation and propagation of ground vibrations.
Chapter 7 has dealt in detail the influence of various parameters on the intensity of ground
vibrations. In some cases even by adjusting these parameters, vibration levels may not be
within the acceptable levels. Under these constrained conditions some surface mines are
resorting to vibration isolation by making trenches or pre-split planes. Though it is
established that discontinuities like fault, pre-split, trench etc attenuate ground vibrations,
many researchers and practicing engineers are of the opinion that field experiments to
ascertain the extent of damping due to a trench or trenches becomes very expensive and
cumbersome. Moreover, unless we have a prior knowledge of the extent of damping achieved
by trenches, pre-split planes etc, it becomes a difficult proposition to practically execute these
techniques. Venkatesh (2002) and Prakash et al (2004) have conducted some experiments
with regard to use of trenches for reducing ground vibrations but it is felt that computer
simulation may prove to be inexpensive, fast and realistic approach to arrive at the design
parameters of a trench to meet the field requirements. Keeping this in view, 3DEC, a distinct
element code is used to simulate opencast blasting to establish the extent of reduction in
vibration intensity due to varying trench depth.