Selecting the Suitable Rock Excavation Method of Hard Rock Removal for Constructing a Ground Level Service Reservoir at Hill Top in Urban Population

Abstract

A best-suited method for rock excavation at the hilltop has been identified in the present paper for construction of a Ground Level Service Reservoir (GLSR) in a densely populated urban area. At the foothill, several residential houses are located at 70 meters from the excavation boundary. Due to presence of hard granitic rock, the previously adopted method using a non-explosive silent cracking agent combined with hydraulic rock breakers and excavators became inefficient in achieving the required production targets. Hence, various alternative rock excavation methods were evaluated considering two key factors, timely completion and safety of nearby structures.

Various rock-breaking techniques such as hydraulic rock breakers, static expansion agents, plasma blasting and heat-assisted splitting were reviewed thoroughly, but they found to be time-consuming and inadequate for completing the project within the time schedule. The use of explosives and controlled blasting method emerged as the only viable option provided the emanating ground vibrations, noise, and flyrock are maintained within permissible limits. Based on data from different sites with similar geological conditions, a vibration prediction equation was developed and accordingly, appropriate controlled blasting patterns along with an optimized excavation methodology were proposed to ensure safe rock excavation within the designated timeframe.