The purpose for Platform blasting is to break the rock sufficiently in order that it can be excavated and removed. To accomplish this, the blaster drills a pattern of holes distributed evenly throughout the rock to be shattered. These holes are then filled with a pre-determined amount of explosives. When these explosives are detonated, they release huge amounts of energy in the form of shock waves and high gas pressure. This energy confined in the rock shatters the surrounding rock and moves it from its original location. A small percentage of the gas pressure escapes into the atmosphere and produces noise and air concussion. The shock wave and the force exerted on the rock produces vibrations in the rock and earth surrounding the blast site.
renches are excavated for installation of oil, water, and sewage pipelines as well as for cables. Blasting of trenches differs from common bench blasting because the width of the blasting round is considerably smaller than its length. Trench blasting is defined as rounds with a width of less than 4 m. A trench blast is more constricted than a normal open pit blast which results in higher explosives consumption per cubic meter of blasted rock. The diameter of the blast holes is normally smaller which provides better distribution of the explosive in the rock and avoids excessive over break outside the theoretical contour. As a rule of thumb, the hole diameter should be 1/60 of the width of the trench, so if the width is 2.0 m the diameter of the hole should be 0.033 m or 33 mm.
Two methods for trench blasting are used: 1. Traditional trench blasting 2. Smooth wall trench blasting.
borrow pit, also known as a sand box, is a term used in construction and civil engineering. It describes an area where material (usually soil,gravel or sand) has been dug for use at another location.
 Borrow pits can be found close to many major construction projects.
For example, soil might be excavated to fill an embankment for a highway, clay might be excavated for use in brick-making, gravel to be used for making concrete, etc.