ABSTRACT:

This paper investigates the predictability of the strength loss of igneous rocks treated with microwave energy. First microwave treatment tests were performed at 6 kW power for the duration of 120s on the core samples of nine different igneous rocks such as granite, syenite and gabbro. Then uniaxial compressive strength (UCS) tests were carried out on the hot specimens. Mineralogical analysis, density and porosity tests were also performed on the samples. The data were evaluated using multiple regression analysis and an estimation equation with very high correlation coefficient was derived for the strength loss. The equation includes UCS, maximum surface temperature, quartz plus feldspar content and porosity values. The statistical test showed that the equation was valid. It was concluded that the derived equation could be used for the estimation of the strength loss of igneous rocks treated with microwave energy.

INTRODUCTION

The mechanized excavation of rocks indicates a rapidly increasing trend in the world. But low advance rate and excessive tool wear are the important difficulties when excavating hard and abrasive rocks. Several studies have been carried out by several researchers to solve these problems. One of the recent studies is the microwave-assisted excavation of hard rocks. Some researchers have studied the effects of microwave irradiation on the mechanical properties of rocks for possible application in the microwave assisted rock excavation.

Basalt was subjected to studies by Satish (2005) and Satish et al. (2006) using low power microwaves (150W). Under the point load test, they saw that a long microwave treatment lead to samples spalling and local chipping. Additionally, several rock samples showed cracking and splitting at high exposure duration. With more exposure time, they noticed that the rock's strength decreased.

Motlagh (2009) looked into how microwave treatment affected the abrasivity and mechanical characteristics of several hard rocks. He demonstrated that after microwave treatment, the uniaxial compressive strength (UCS) values of almost all samples reduced by roughly 30%. Considerable decrease in Brazilian tensile strength (BTS) was seen in some samples. Nearly all samples exhibited a drop of roughly 30% in the Cerchar abrasivity index.

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