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《Journal of Engineering Geology》 2005-01
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CEMENTS OF SAND LOESS AND THEIR CEMENTATION IN NORTH SHAANXI AND WEST SHANXI

ZHANG Yongshuang ①QU Yongxin ② (①Institute of Geomechanics, Chinese Academy of Geological Sciences,Beijing 100081) (②Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029)  
Based on field investigation, using multiple methods including SEM, XRD, as well as soil physics and soil chemistry methods, the particle composition, aggregate, and cement composition were measured on 48 samples of Malan loess from 12 counties of north Shaanxi province and west Shanxi province. The test results indicate that the cements, including clay minerals, super fine-grained carbonate, free oxides, and organic materials, mainly exist as a aggregate coat on the grain surface, and form weak cementation between the frameworks of sand loess. The clay minerals and organic materials in sand loess have weak cementation only in dry state because it is not stable in water. Calcium carbonates (CaCO 3) in sand loess exist as both coarse grains and fine grains, forming the framework and cementation. The super fine grain is a kind of irreversible cementing material, which plays an important role in the course of aggregate formation, preservation, as well as connection between aggregates and debris grains. The contents of amorphous oxides (SiO 2、Fe 2O 3、Al 2O 3) are low, but they should not be ignored in the cementation of sand loess because of their interaction with other cements on the grain surface. Based on the statistic analysis, the aggregation coefficient can reflect the cementation degree of sand loess, which establishes a bridge (strong relationship) between cementation and physical-mechanical properties of loess. The study of cement composition and their cementation mechanisms not only helps us to have a better understating of the engineering properties of sand loess, but also provides a better insight into the supergene geochemical environment of loess plateau of China.
【Fund】: 国家自然科学基金资助项目(No.40102025).
【CateGory Index】: P642.1
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