The Relationship between Characteristics and Shear Strength of Structural Planes and its Effect on the Stability of Landslide

In this paper, the shear strength of different structural planes are tested with the hand portable shear tester in site. The study shows that the shear strength of the structural plane in the granite mass is mainly related to the roughness, the degree of cementation and interlocking of the structural plane. The shear strength of the smooth plane is less, and the plane with interlock partly is larger. In the tests basis, the paper posts out the relation between τ and σ, which can be used to calculate the stability of the landslide。

Pedogenic formation of smectites in a vertisol developed from granitic rock from Kaélé (Cameroon, Central Africa)

Smectite formation in a vertisol developed from a granitic parent rock in the Kaélé region of Cameroon in a tropical, dry climate was studied by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), chemical analyses, cation exchange capacity (CEC) and low temperature gas adsorption. The soil profile comprises three horizons (from base to top): (1) a saprolite, (2) an intermediate horizon, and (3) an upper dark grey horizon. In the saprolite, the progressive alteration of feldspars gave rise to the exclusive neoformation of beidellite exhibiting a typical honeycomb fabric. This process resulted in Al, Fe, Ca, Mg, Ti and Mn enrichment, a depletion of Si and Na and a significant negative Eu anomaly. In the upper horizons, beidellite evolves and is transformed into montmorillonite and kaolinite, probably through a series of smectite-kaolinite mixed layers. This transformation, from the saprolite to the upper horizons, causes the observed decrease in the CEC and the increase in specific surface area and mesoporosity of the clay. The REE patterns of the bulk soil and clay fraction display similar behaviour, indicating that the three horizons, and hence the clay minerals, have a common source in the underlying granite. Mass-balance calculations show that the intense weathering of the granite leads to a mass reduction of ~80–90%.