Article
ADVANCED CONTROLLED BLASTING TECHNIQUES FOR ROAD CONSTRUCTION IN MOUNTAINOUS REGIONS
Drill and blast method continue to be the preferred method of rock excavation worldwide. Blasting causes damage to the surrounding rock mass. In surface excavation with desired slopes, over break and damage to the final slope of excavation adversely affect safety as well as economics of the project. Various controlled blasting operations are line drilling, trim blasting, buffer blasting and presplitting blasting technique used by practicing engineers to restrict damage to surrounding rock mass along the final wall of excavation and to achieve desired slope. Pre-splitting is the commonly used controlled blasting technique for perimeter control in mining and construction industries. Apart from unsafe slope at the perimeter of rock excavation, pre-split blasting techniques prevents extra cost of rock excavation, backfill material and rock reinforcement. This technique has several advantages such as minimum damage from back-break, higher structural stability and stable final pit walls or slope at the designed angle thus improving overall safety of wall / slope. This paper presents a review of different commonly used controlled blasting techniques highlighting pre-splitting technique through a case study of Kol dam hydroelectric power project (KHEPP). This 800 MW project is constructed on river Satluj in Himalaya, India. The excavation in the project consists of preparation of seven benches having slope of 1:4 in predominantly pink limestone and yellowish dolomite, intensely folded, and posing geological challenges for the safe excavation due to intense folding and parallel joints spacing ranging from 0.30m to 2m. The joint set in limestone and dolomite made whole rock formation in a block size with surface area ranging from as small as 0.5m2 to as large as 5.0m2 . The block formation was prone to over-break leading to unstable slope. An innovative approach has been adopted for improving drilling accuracy and modified pre-splitting controlled blasting techniques at Kol dam hydro power project to achieve stable slopes and minimum rock mass damage. The paper provides insight to presplit controlled blasting techniques and successful implementation
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