Evaluating the Application of Rock Breakage without Explosives in Underground Construction—A Critical Review of Chemical Demolition Agents

Abstract

The method of drilling and blasting with explosives is widely used in rock fragmentation applications in underground construction projects, such as tunnels and caverns. However, the use of explosives is associated with rigorous safety and environmental constraints, since blasting creates toxic fumes, ground vibrations, and dust. Because of these constraints, there has been a growing interest in transitioning away from explosives-based rock fragmentation. The use of explosives-free methods could lead to continuous operation by eliminating the need for idle time with additional ventilation required to exhaust the blast fumes. This paper first presents a critical review of various methods that have been developed so far for rock fragmentation without explosives. Such methods include thermal fragmentation, plasma blasting, controlled foam injection, radial-axial splitter, and supercritical carbon dioxide. Thermal fragmentation, as the name implies, uses high heat to spall high-grade ore. However, it requires high heat energy, which requires additional ventilation as compared to normal conditions to cool the work area. Plasma blasting uses a high temperature and pressure plasma to fracture rock in a safe manner. While this method may be environmentally friendly, its usage may significantly slow tunnel development due to the need to haul one or more large energy capacitor banks into and out of the work area repeatedly. Controlled foam injection is another chemical method, whereby foam is the medium for fracturing. Although claimed to be environmentally friendly, it may still pose safety risks such as air blast or flyrock due to its dynamic nature. A radial-axial splitter (RASP) is an instrument specially designed to fracture a borehole in the rock face but only at the pace of one hole at a time. Supercritical carbon dioxide is used with the equipment designed to provide a high-pressure jet stream to fracture rock, and replaces water in these instruments. The method of soundless chemical demolition agents (SCDA) is evaluated in more detail and its merits over others are highlighted, making it a potentially viable alternative to blasting with explosives in underground excavation applications. Future work involves the optimization of SCDA for implementation in underground mines. The discussion compares the key features and limitations, and future work needs are underlined.

Directional fracturing of rock by soundless chemical demolition agents

“…Conventionally SCDAs have been used in the demolition of concrete structures, and parts of buildings in urban settings [ [44] , [45] , [46] , [47] ]. Less commonly, SCDA was used in mining, for hard rock breakage or tunneling.…”

Evaluation of Slow-Releasing Energy Material (SREMA) Injection for In-Situ Rock Breaking Under Uniaxial and Triaxial Loading: An Experimental Study

“…In addition, SCDA-based fracturing is a potential preconditioning technique that can be exploited in the extraction of unconventional natural gases such as shale gas, gas hydrates and coalbed methane recovery (Guo et al 2015;Tang et al 2017bTang et al , 2021Zhai et al 2018;). It has also gained popularity in underground excavations (Chen et al 2023;Habib et al 2022).…”

Multifractal Characteristics of Smooth Blasting Overbreak in Extra-Long Hard Rock Tunnel

“…It is well-known that new blasting methods such as supercritical carbon dioxide, soundless chemical demolition agents, and high-pressure gas expansion have the advantages of safety and environmental protection [20,21]. These new blasting methods can effectively control the overbreak and underbreak problems of tunnel blasting.…”