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The shear mechanical behavior of weak interlayer is of great significance for the stability analysis of landslides. Based on the shear deformation-failure characteristics of weak interlayer soil and the clay damage theory, a shear failure mode is proposed to describe this kind of phenomenon. Triaxial compression tests and numerical simulation are conducted on weak-interlayer samples at conditions of different confining pressures and inclination angles. The numerical and experimental results show basically good agreement for both the peak strength and failure patterns. With increases in the thickness and dip angle (in the range of 0°–60°) of the weak interlayer, the shear strength of the samples decreased gradually. The weak-interlayer samples having a low dip angle were crushed and inflated; when the dip angle exceeded 15°, there was shear slip along the weak interlayer; when the weak interlayer was thin, the sample sheared along the structural plane; when the weak interlayer was thick, there was extrusion inside the weak interlayer or shear slip along the contact surface of the weak interlayer and mudstone. These results can improve our understanding of the mechanical behavior of mudstone rock mass with weak interlayers and can be used to analyze the stability of rock slopes or other rock engineering cases such as tunneling construction in rock mass with weak interlayers. [ABSTRACT FROM AUTHOR]

The response of a loess-mudstone landslide model to seismic activity is examined using centrifuge shaking table tests and 2D seismic input waves. The physical model of a dormant landslide is subjected to simulated seismic signals of different input amplitudes, and the dynamic response is analyzed in terms of relative peak ground acceleration (PGA), which is used to assess deformation and failure mechanisms of the slope. Relative PGA increases with increasing landslide height, reaching maximum values at the crest, while values at the toe are slightly larger than those in the middle of the slope. Relative PGA is the highest along the outer surface and weakest along the sliding surface. Horizontal values are generally larger than vertical values, and the amplitude of the seismic input strongly affects the landslide dynamic response. The PGA amplification factors increase considerably with increasing input amplitude, reaching maximum values at 0.3-0.4 g, and then decrease. The largest displacement is observed at the crest, while displacements in the middle part and at the toe increase steadily with higher input amplitudes, and displacement at the crest increases at a higher, irregular rate. Deformation is most apparent at the crest, developing from cracks into collapsed soil deposited at the toe. Local shallow sliding is observed along the landslide surface, and the dormant sliding body may generate displacement along the sliding surface caused by earthquake reactivation. A numerical model of the landslide provides results consistent with centrifuge model testing; both indicate similarity in seismically induced dynamic responses and failure characteristics. [ABSTRACT FROM AUTHOR]

Dynamic behavior and failure mechanism of slope during earthquake are hot topics in geotechnical engineering community. In Tianshui area, Northwest of China, the deformation features of loess-mudstone slopes induced by earthquakes are still not well understood. The current study aims to discuss the dynamic behavior of the slope under earthquake, by performing a series of centrifuge shaking table tests and numerical simulations. The results are processed for PGA amplificatory effect study and to evaluate the earthquake induced deformation mechanism. Better agreement is obtained between the results of numerical simulations and centrifuge tests. The results indicated that the acceleration response of the loess-mudstone slope showed several amplifying characteristic: the height effect, lithologic effect and surface effect. It also proves that the displacements in the loess layer are much larger than mudstone. As the input amplitude increased, the shear plastic zone developed along a further slide surface. Tension plastic zone mainly occurred at the crest. Roughly, the regions of earthquake induced deformation state increased with the increase in amplitude of earthquake wave. Deformations occurred at the upper part of the slope. Tensile cracks evolved on the crest and the upper part of slope in loess layer, moreover, failures occurred at slope surface, and only slight deformation at slope toe. Deformations with continuous shear cracks and slope surface upheavals developed at the middle part of slope. [ABSTRACT FROM AUTHOR]