| dc.description.abstract | The critical displacement is referred to as a threshold of a slope from stable to unstable, compared with the calculated permanent displacement under seismic load using Newmark displacement analysis. The critical displacement, usually obtained from laboratory shear tests under constant/low shear rates, is defined as the coseismic displacement beyond which strengths along sliding surface approach residual values. The typical values ranges from several centimeters to several tens of centimeters, which depends on the sheared materials. However, this definition of the critical displacement is oversimplified because the strengths along sliding surface is velocity-dependent. Therefore, we collect a large number of parameters which change with different materials of friction tests in order to take into account velocity dependence. Besides, this study redefines critical displacement as the accumulated displacement before initiation and discusses how the critical displacement changes with different dominant frequencies and materials. A simple two dimensional rigid block model incorporating velocity-displacement dependent friction law on sliding plane is adopted. The inclination of the sliding plane is assumed as 15°. The seismic load is simplified as sinusoidal wave with peak ground acceleration of 600 gal. Different seismic frequencies of 0.5, 1.2, 2.0 Hz are used to evaluate the influence of dominant frequency on the critical displacement. The influence of the parameters in the displacement/velocity dependent friction law on the occurrence of block instability is also assessed. Firstly, this study reveals the leading cause which results in catastrophic failures. Secondly, we discuss how material, dominant frequency, peak ground motion acceleration and dip angle of sliding surface influence the critical displacement. Catastrophic failures will not form if the strengths of sliding surface are either not easy to decrease with increasing velocity or remains high under ultrahigh-speed shearing. In addition, if catastrophic failures occur, we find that the higher the peak friction coefficient, steady-state friction coefficient at infinite velocity, slip weakening distance, and critical velocity of material, the higher the critical displacement. In particular, slip weakening distance have great influence on critical displacement. Moreover, the critical displacement is also affected by dominant frequency but not peak ground motion acceleration. Being not affected by peak ground motion acceleration mainly because of the input sinusoidal wave. This study highlights the initiation of landslides and the critical displacement are extremely complex, both obviously rely on materials. Also, velocity-displacement dependent friction law must be taken into account for landslide triggering assessments. | en_US |