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Featured Application: An integrated dynamic model has been proposed, which can be used to analyze landslides with significant changes in dynamic characteristics due to changes in the integrity of the landslide mass. The analysis results can be directly applied to landslide prevention and mitigation applications based on geographic information systems (GIS). Landslides are one of the most common catastrophic mass flows in mountainous areas. The occurrence of fragmentation leads to the evolution of the integrity and stiffness of the sliding mass. The changes in internal composition caused by basal erosion and entrainment make the dynamic evolution of landslides more complex. To consider these complex processes, physics-based dynamic models are often used to analyze the dynamic characteristics of landslides. However, the proprietary assumptions of dynamic models often limit their application to complex events. A single dynamic model is often not competent for the analysis of landslides with evolving dynamic characteristics. In this study, two dynamic models are effectively integrated according to the evolving characteristics of the landslide. The common effects of basal erosion and entrainment are also considered. The maximum sliding velocity, accumulation range, and erosion depth characteristics of this integrated dynamic model are more consistent with the field than those of the single dynamic model. Under the terrain conditions of this study, within a few seconds of the triggering stage, if the occurrence of disintegration is advanced by 2 s, the maximum impact area will increase by about 3.1% to 4.1%, and the maximum kinetic energy will increase by more than 20%. Simulation results indicate that the changes in the integrity of the landslide body significantly affect the evolution of subsequent landslide dynamic characteristics. [ABSTRACT FROM AUTHOR]

Landslides are one of the most common catastrophic mass flows in mountainous areas. The occurrence of fragmentation leads to the evolution of the integrity and stiffness of the sliding mass. The changes in internal composition caused by basal erosion and entrainment make the dynamic evolution of landslides more complex. To consider these complex processes, physics-based dynamic models are often used to analyze the dynamic characteristics of landslides. However, the proprietary assumptions of dynamic models often limit their application to complex events. A single dynamic model is often not competent for the analysis of landslides with evolving dynamic characteristics. In this study, two dynamic models are effectively integrated according to the evolving characteristics of the landslide. The common effects of basal erosion and entrainment are also considered. The maximum sliding velocity, accumulation range, and erosion depth characteristics of this integrated dynamic model are more consistent with the field than those of the single dynamic model. Under the terrain conditions of this study, within a few seconds of the triggering stage, if the occurrence of disintegration is advanced by 2 s, the maximum impact area will increase by about 3.1% to 4.1%, and the maximum kinetic energy will increase by more than 20%. Simulation results indicate that the changes in the integrity of the landslide body significantly affect the evolution of subsequent landslide dynamic characteristics.

The Newmark sliding block method is widely used to assess the seismic performance of earth slopes by calculating the permanent displacement of the simplified sliding mass. The conventional Newmark method models the potential landslide mass as a single rigid block sliding on a well-defined slip surface. In this study, a multi-block approach to calculate the sliding displacement of slopes is presented. The dynamic equation of a series of rigid blocks in different sliding conditions is established and the complex interactions within the slip episodes of rigid block assemblies are explicitly resolved. The results show that the original Newmark single block method may produce unconservative estimates of permanent displacement of the shallow sliding mass when the deep-seated sliding subsequently occurs during the earthquake. The predicted displacement of the upper sliding mass, which is simplified as a summation of the Newmark displacement of each single sliding mass, may either overestimate or underestimate the computed displacement including the coupling of sliding of multiple soil masses. The developed approach extends the well-accepted Newmark sliding block method, and can serve as an alternative to predict the seismic slope displacement in which multiple failure surfaces are expected during earthquakes. • An explicit physics-based multi-block sliding model is presented. • The complex interactions within the slip episodes of rigid block assemblies are explicitly resolved. • The developed approach is an extension of the well-accepted Newmark sliding block method. • The model can be applied to evaluate the seismic permanent displacement of slopes with multiple failure surfaces. [ABSTRACT FROM AUTHOR]

The work considers critical slopes located at regions with high danger and proposes a method which approximately predicts the risk of earthquake-induced excessive movement of these slopes, in the case where relevant soil strength data along their slip surface do not exist. The method utilizes (1) simplified constitutive equations predicting soil response along slip surfaces and (2) a multi-block sliding system model, both recently proposed. It involves the following steps: (a) collect relevant topographic information and laboratory test results of past landslides at the region of interest, (b) (i) analyze the relevant laboratory tests to estimate the soil constitutive parameters and (ii) estimate the mobilized residual soil strength by back analysis of relevant past landslides, (c) select constitutive model parameters for future applications at the region based on step (b) and validate them based on analysis of the triggering of the past landslides and (d) apply the selected constitutive model parameters in critical slopes in the region under consideration to predict not only whether triggering occurs, but also the post-triggering slide deformation. The paper, after describing in detail the proposed method, applies it at the Wenchuan region, where the 12th May 2008 earthquake triggered many landslides. During the application, four ring shear test results and twelve landslides of the 12th May 2008 earthquake were considered. The application was successful and the following were observed: (i) in the back analyses, the multi-block model predicted reasonably well the final configuration of all slides, (ii) apart from two significantly larger back-estimated values of the residual soil strength, small scatter existed in the other back-estimated values and (iii) the selected model parameters were duly validated under step (c). Furthermore, as the back-estimated friction angle of most landslides was less than 18°, and the materials along the slip surface have a Liquid Limit value less than 25 %, it is inferred that some, or all of the slip surface during these slides, was sheared in an undrained manner. [ABSTRACT FROM AUTHOR]

A multi-block sliding model has been proposed in order to simulate the actual geometry of landslides and their rotation with displacement. The governing equation of motion was formulated with the force equilibrium approach and solved by numerical integration in terms of time. The present work derives the formulation of the multi-block model based on another perspective, the energy conservation principle. This approach, in contrast to the force equilibrium approach, has the ability to derive analytical equations predicting the distance moved of masses sliding with resistance exhibiting both cohesional and frictional components. The most general geometry, where analytical solution predicting post-failure displacement can be obtained, is considered. Then, and as this equation is complex, a simple special case geometry is considered in order to derive easy-to-apply simple expressions which predict post-failure landslide displacement in terms of soil resistance and geometric parameters of the sliding mass. The accuracy of this approximate for general geometries expression is validated by extensive parametric analyses. [ABSTRACT FROM AUTHOR]

The paper first proposes and validates a constitutive model simulating the change of resistance along slip surfaces in sands both for the undrained and drained cases, measured in ring shear tests. The proposed model is based on (a) the critical state theory and (b) the assumption that the critical state changes as a result of grain crushing, in terms of shear displacement. Model parameters depend only on sand type. Then, the developed constitutive model is implemented in the recently-proposed multi-block sliding system model for the prediction of the triggering and deformation of earthquake-induced landslides. The improved model is applied successfully at a simple slope and at the well-documented Nikawa slide triggered by the 1995 Hyogoken-nambu earthquake. Parametric analyses illustrated the ability of the improved model to simulate the effect of the applied motion, sand density, saturation conditions and geometric rearrangement on the seismic displacement of slopes. [ABSTRACT FROM AUTHOR]

The paper first proposes and validates a constitutive model simulating the change of resistance along a slip surface of clay for both the undrained and drained cases. The proposed model is based on (a) the critical state theory and (b) the assumption that the critical state changes once failure is reached, in terms of the further shear displacement. Under undrained conditions, the proposed model simulates the excess pore pressure generation and, subsequently, the continuous change of resistance along the slip surface from its initial value to the peak strength and then, at large displacement, the residual value. The latter can be measured in constant-volume ring shear tests. Then, the developed constitutive model is implemented in the multi-block sliding system model for the prediction of the triggering and deformation of slides. The improved model is applied at the well-documented Fourth Avenue landslide of the 1964 Alaska earthquake. [ABSTRACT FROM AUTHOR]