The controlling factors of dolomite uniaxial compressive strength - A case study from the area of Aohua, Yilan and Mt. Mugua, Hualien, eastern Taiwan

• Main Authors: Jin-Tsuen Lin, 林錦村
• Other Authors: Ying-San Liou
• Format: Others
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/zmuu2x

碩士 === 國立東華大學 === 自然資源與環境學系 === 102 === Uniaxial compressive strength, one of the most used rock physical strength indexes, is important as an indicator of the rock stiffness for assessing Rock Mass Rating. The strength is a criterion chosen in designing mining engineering and tunnel engineering alike, the selection of machinery toolsand its efficiency, and working safety design. Previous studies shown thatthe average uniaxial compressive strength of dolomite in Aohua, Yilan and Mt. Mugua, Hualienwere 83.71 and 195.56MPa, respectively. Dolomite samples collected from the study area were analyzed using optical microscope, scanning electron microscope, X-ray powder diffractometer, and X-ray fluorescencespectrometer in order to understand the relationships between the uniaxial compressive strengthof the rock and its crystalline grain size, minerals and chemical composition, apparent specific gravity, water absorbing rate and porosity. In addition, these results were also compared with dolomitesfrom Ho-Zen, Hualien, to clarify the relationships between micro structures and rock strength of the dolomite. The results indicate that mineral compositions from different localities are similar containing 80-98% of dolomite, 0.2-20% of calcite, minor amounts of chlorite, apatite, talc, titanite, and iron oxides. The discrepancy of rock strengths between different localities is mainly due to its crystalline grain size. The smaller of the grain size, the stronger of the rock strength is. Littlerelevances were found between the rock strength and their chemical composition, apparent specific gravity, porosity, and waterabsorbing rate.The grain size distribution of dolomite from Aohua, YilanandHualien Ho-Zen and Mt. Muguademonstrates a southwarddecreasing trend, while the rock strengths show aoppositetrend; i.e., the rock strength is increasing as its grain size decreasing. Additionally, the width of the calcite twins measured by using optical microscopeis very different in dolomites collected from three localities, >1μminAohua’ssamples, ≒1μminHo-Zen’s dolomite, and in Mt. Mugua’s samplesthere is no clear twins observed. Based on the results of the calcite twin, the metamorphic temperatures were calculated around 150℃〜300℃ in Aohua, <200℃ in Ho-Zen,and even lower temperaturein Mt. Mugua .