Sung-Kun Choi

Shear Strength of Artificially Cemented Sands

In this study, a series of drained triaxial tests were performed in order to examine the effect of cementation on the shear behavior of granular soil. It was observed that the brittle nature and dilative tendency of granular soil is dominant under a low confining stress level, while high confining stress results in a contractive behavior despite the strong cementation bond. Based on experimental results, an idealized concept is suggested to define the shear strength of cemented sand in three distinctive zones: the cementation control zone with a constant cohesion intercept at a low confining stress level, the transition zone in which the cohesion intercept is gradually reduced after a breaking point, and the stress control zone with almost zero cohesion intercept due to breakage of cementation bonds at a high confining stress level. It was shown that the sitting pressures during cementation have little effect on the strength parameters of cemented sand, while the increase of gypsum content and relative density, and the decrease of particle size, result in an increase of the cohesion intercept and the breaking point. In addition, the prediction equations for the shear strength and cohesion intercept in the cementation control zone and the transition zone are suggested from the analytical and experimental interpretation.

Stable isotope systematics of Ulsan FeW skarn deposit, Korea

Abstract From the measurements of oxygen and carbon isotope ratios (δ 13 C=1.2–4.6 relative to V-PDB, and δ18O=13.5–22.1 ℵrelative to V-SMOW) of fresh or partly altered limestones at the Ulsan skarn deposit, it is suggested that the origin of carbonate rocks is marine carbonate rather than carbonatite. Moreover, the calculated isotopic compositions (δ 13 C=−7.67 ℵ and δ 18 O=6.75 ℵ) of the hydrothermal fluid in the main Fe stage of skarn formation imply that this fluid was magmatic water derived from differentiated granitic melts. At this prograde stage, carbon and oxygen isotope data of skarn calcites show that X CO 2 was low ( Pb Ag mineralization was inferred not only from the oxygen isotope ratios of siderite, but also from the fluid inclusion data of later quartz-siderite veins. This temperature drop reflects an important change in the hydrology of the hydrothermal system at this vein stage (i.e., mixing with meteoric water).