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High-Temperature Plasma Associate Professor, School of Civil & Environmental Engineering, James R. Beaver Geotechnical Engineer, Hart-Crowser Inc. |
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INVITED PAPER |
ABSTRACT
The use of plasma technology as a high thermal treatment for in-situ applications involving ground modification and geoenvironmental remediation was investigated in a series of laboratory chamber tests. Two sizes of nontransferred arc plasma torches were used to melt soil into magma in a quick and efficient manner. Within five minutes exposure to a plasma flame positoned in a downhole configuration, the very high arc temperatures of 4000°C to 7000°C created a pool of molten lava at the center of each soil deposit. Subsequent cooling of the melt formed a variety of artificial igneous rock products, ranging from variable colored glassy obsidians to microcrystalline granites and basalts.
The effect of soil mineralogy on the efficiency and product formation by plasma vitrification was studied using four different soils in cylindrical steel chambers. The soil types included: clean natural quartz sand, clean manufactured (crushed) sand, very silty fine sand, and natural kaolinitc clay. Measurements of mass density, void ratio and porosity, compressive strength, and small-strain stiffness from nondestructive wave velocity for the original soils and vitrified rock materials were obtained to quantify the degree of improvement in geomaterial properties. Testing investigated the relative influences of applied plasma power level (100-kW and 240-kW torch systems), energy consumption, initial soil type and mineralogy, and prepared moisture content on the final size and mass of the igneous rock products.
KEYWORDS: basalt, clay, granite, ground improvement, heating,lava, magma, melting, obsidian, plasma, rock, sand, shear modulus,soil remediation, stiffness, strength testing, temperature, vitrification, wave velocity
