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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]

Tianshui City is located in a seismically active region of China. Historically, many earthquakes with magnitudes of 6.0-8.0 have been reported in this area, and most of loess-red mudstone landslides in this area are known to have been triggered by earthquakes. However, the soil dynamics under earthquakes in the Tianshui area have been little studied. Therefore, to understand the dynamic stress-strain behavior of undisturbed soils during the earthquake, cyclic and shear strength tests were conducted on soil samples (loess and weathered red mudstone) obtained from Tianshui in a cyclic triaxial test system. Two types of laboratory tests were carried out on two kinds of soils. The first type involved the tests with different cyclic stress ratios applied and the number of cycles N more than 20, while the second type are series of stress-controlled undrained reverse-shear tests. By doing so, the differences on stress condition on the behavior of Young's modulus E , stress-strain and shear strength were measured. In addition, tests modeling natural seismic loading were also carried out for comparative purposes. Some residual shear behaviors were also recognized. The results of a series of tests designed to study the stress-strain behavior of undisturbed soils under repeated loading are presented. These tests will provide useful parameters (e.g. λ and E ) for analysis of slope stability during earthquakes and earthquake-resistant design. [ABSTRACT FROM AUTHOR]