| Summary: | 碩士 === 國立臺北科技大學 === 資源工程研究所 === 100 === In nature, weathering reduces rock strength and increases its deformability. It is, therefore, an important factor which needs to be considered for designing safe engineering structures. The rock weathering zone and degree of weathering are also important for geological investigation.
This study aims to clarify weathering mechanism of rock and to determine the variation of the mechanical and the mineralogical properties during weathering process which produced by means of artificial circulations on rapidly changing of environmental temperature and moisture conditions.
Test results show that intercalated of sandstone and shale has weak bonding strength for the inter-bed and weather rapidly as the cementing material dissolved in water. The plane paralleling the inter-bad is the critical one for weathering failure. For marble, calcite dissolves during artificial weathering cycle and leads to increase in porosity and water absorption. Rock strength is reduced due to descending grain contacts. For serpentinite, mineral dissolution and phenomenon of phase transition are observed during artificial weathering, which increases porosity in mineral grains and reduces the mineral contacts. We infer that the quartz formed from phase transition is helpful for the bonding between grains. Therefore, the strength of weathering resistance and mechanical properties exhibit cyclic variation with a raising trend.
Test results for the capability of carbon dioxide adsorption show that magnesium and calcium in the intercalated of sandstone and shale and the serpentinite can absorb carbon dioxide with an increasing as the artificial weathering cycles. Results of regression analysis show that the capabilities of carbon dioxide adsorption highly correlate with their mechanical properties. It is believed that mineral phase transition occurs during artificial weathering process, leads to variation on physical index and microstructure of the rocks and changing their mechanical characteristics.
Numerical simulation results show that the strength of the meso-scale specimen and compositional micro-grain for marble descend during artificial weathering process, and conversely for serpentinite, which match with laboratory results.
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