EGU21-14242
https://doi.org/10.5194/egusphere-egu21-14242
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Oxidative weathering deterioration of black shale and its bedding shear failure modeling

Chunwei Sun1,2, Marc-Henri Derron1, Michel Jaboyedoff1, and Xiyong Wu2
Chunwei Sun et al.
  • 1Institute of Earth Sciences, University of Lausanne, 1015 Lausanne, Switzerland
  • 2Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu, Sichuan Province 611756, P.R. China

This work investigated the oxidative weathering deterioration of black shale along a bedding slip zone and how it affects the bedding shear failure in the Xujiaping landslide, southern Sichuan Province in China. Many dissolved pits were found on the limestone, and part of the black shale in the slip zone is mud-like and clastic, showing local shear failure, which can be one of the main reasons of slope instabiliy. The microstructure of black shale under oxidative weathering condition was observed by scaning electron microscopy (SEM), characterized by dissolved pores, weathering crust (iron sulfate) of pyrite crystals, and the filling gypsum crystal in the bedding foliation. The deterioration mechanism was expanded: (i) rock-forming and carbonate minerals were especially prone to dissolution by sulfuric acid from black shale oxidation in the slip zone, and (ii) volume expansion due to the crystallization force of precipitated minerals caused further fracture expansion and deformation. Therefore, two theoretical models were developed that use stoichiometric calculations of pyrite and calcite to determine the dissolution rate and the rock structure after chemical weathering; and establish a rock structure model characterized by foliation weakening of gypsum crystallization. In order to analyze the landslide failure, discrete element method (DEM) is used to analyze the black shale shear failure mechanism of the two degradation models after oxidative weathering. It will be useful to better understand how these oxidative weathering deterioration contribute to bedding shear failure in natural hazards.

How to cite: Sun, C., Derron, M.-H., Jaboyedoff, M., and Wu, X.: Oxidative weathering deterioration of black shale and its bedding shear failure modeling, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14242, https://doi.org/10.5194/egusphere-egu21-14242, 2021.

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