Formation and evolution of Emeishan basalt saprolite in vadose zones of Touzhai landslide source rockmass  

作　　者：YANG Ji-qing XU Ze-min ZHANG Rui CHEN Ji-pu REN Zhe LUO Rong-zhang ZHANG Xiu-shuo 

机构地区：[1]Faculty of Civil Engineering and Mechanics, Kunming University of Science and Technology [2]College of Architectural Engineering, Yunnan Agricultural University

出　　处：《Journal of Mountain Science》2017年第6期1174-1184,共11页山地科学学报（英文）

基　　金：funded by the Joint Funds of the Natural Science Foundation of China with the Natural Science Foundation of Yunnan (Grant No. U1502232,U1033601);the Research Fund for the Doctoral Program of Higher Education of China(Grant No. 20135314110005)

摘　　要：In order to explain the formation process of slope hazards, and to identify the key factors leading to instability of a slope, Emeishan basalt saprolite in vadose zones of the Touzhai landslide in Zhaotong, Yunnan, was studied. The formation and evolution of Emeishan basalt saprolite was examined using, amongst other techniques, field investigations,thin section analysis, scanning electron microscopy(SEM) observations, chemical analysis, physical and water-physical property tests of rock masses. Field observations revealed that the majority of the weathered rock blocks were presented as a concentric layer structure in which an internal corestone was enveloped with several layers of external saprolized crust. Chemical and mineralogical analysis identified that iron was the most sensitive element and that the weathering progress usually started with the oxidation of Fe2+ to Fe3+ in rock blocks. Alkaline elements such as Si, Ca, Mg, Na and K were also dissolved and Fe and Al were concentrated in saprolized crusts. Results indicated that loss on ignition(LOI) also increased significantly. SEM results showed that the weathering intensity of thebasalt blocks decreased gradually from the outside to the inside, and the mineral morphology significantly differed on both sides of the weathering front. The saprolized crusts presented cellular microstructure features due to the generation of micropore and clay minerals. Thin section analysis showed that plagioclase was relatively more stable than pyroxene and chlorite during weathering. With a centripetal propagation of the weathering front, saprolized crusts became thicker and corestones became smaller; fresh Emeishan basalt blocks gradually turned into saprolized blocks. Due to the loose structure and low strength of saprolite, the quality of the Emeishan basalt mass significantly deteriorated, this being a potentially important factor which caused the Touzhai landslide to occur.

关 键 词：Vadose zone Emeishan basalt Scanning electron microscopy Saprolite Corestone Touzhai landslide 

分 类 号：P642.22[天文地球—工程地质学]