Effect of rock properties on rippability of laterite in Iron Ore mines of Goa

Abstract

Ripping is an environmental friendly rock excavation technique and commonly used in surface mines. The present study was conducted in iron ore mines of Goa, where different type of rock material was present like laterite, manganiferous clay, phyllitic clay, banded hematite quartzite/banded magnetite quartzite (BHQ/BMQ), quartz chlorite schist (QCS), dolomite, limonite, kynite etc which requires different excavation method and machineries. Hard lateritic cover and lumpy lateritic ore is common in iron ore mines Goa, which is generally removed by deploying ripper dozers of different capacities mainly depending on the rippability of lateritic boulders buried inside the rock-soil mixture. The study was mainly focusing on lateritic rock material, and an attempt was made to characterize lateritic rock material in four different types, namely indurated laterite (ILT), laterite (LT), laterite clay (LTC) and lumpy laterite (LLT), and research embody the effect of rock properties on rippability of these lateritic rock materials. Rock material properties such as uniaxial compressive strength (UCS) [5.09 - 22.65 MPa], point load strength (PLS) [0.5-3.35 MPa], indirect tensile strength (ITS) [0.76 - 2.81 MPa], sonic wave velocity (P-wave) [1250-3115 m/s], cerchar abrasivity index (CAI) [0.40-2.55], in-situ density [1.58 - 3.20 g/cc], moisture content [1.74 - 4.76 %], slake durability index [72.44-90.25 %], schmidt rebound number [13 - 37], discontinuity spacing [15 - 37 cm], core recovery [18 - 64 %], rock quality designation (RQD) [14-35] were determined to understand their effect on ripper production. Introduction of cerchar abrasivity index (CAI) concept to relate rippability and ripper performance in lateritic rock material is the new contribution. Direct ripping run by Komat'su D275 and Komat'su D355A-3 single shank giant ripper dozer was observed for volume-time calculation and results ranging between 169 - 408 m3/hr. From the study it is observed that lateritic rock material can be categorized into four different ways to understand rippability in laterite and ripper production.