A Framework for Simulating the Evolution of Underwater Landslides and Its Application to Slope Failures in Swiss Lakes

Destructive underwater mass movements can impose a threat to off-shore infrastructure and near-shore communities. Yet predicting their formation and failure mechanisms remains a major challenge, in part due of the large variety of factors affecting their stability over time. Long-term processes such as sedimentation as well as short-term events such as earthquakes can impact the stability of the slope highlighting the need for an integrated analysis procedure to quantify their impact. In this article, such a framework is presented to simulate the evolution of subaqueous landslides, ranging from sediment deposition to seismic triggering to the postfailure evolution of the collapsing soil mass. Each stage is simulated in an individual step, based on different finite element-based methodologies, to best model the governing processes. The steps are linked in a consistent manner to facilitate the simulation of the landslide evolution as a continuous process. The presented framework is applied to analyze three historical landslide events in Swiss lakes. The model predictions compare well with the in situ landslide deposits. The simulation results provide insight into slope failure mechanisms and effects of seismic ground motion characteristics on the stability of the analyzed slope failures.ISSN:1090-0241ISSN:1943-560

Controlling factors for post-failure evolution of subaqueous landslides

Subaqueous slope failures can evolve in various patterns. Whereas some slides run out and furtherevolve into highly mobile turbidity currents, others maintain a continuum-like structure and remainfrontally confined. The different failure modes impose different hazard scenarios, making anunderstanding of their origin crucial for reliable hazard assessments. Yet many of the factorscontrolling their post-failure behaviour remain not well understood. In this paper, a procedure ispresented for the analysis of the post-failure evolution of subaqueous landslides, using a coupledEulerian–Lagrangian finite-element analysis approach. The procedure is applied to analyse the StNiklausen slide in Lake Lucerne (Switzerland), providing a good prediction of observed landslidefeatures, without back-calibration of input parameters. The approach is further applied to investigatethe influence of controlling parameters, highlighting effects of different strength parameters, thesurrounding water and the slope stratigraphy and geometry on the landslide dynamics. The procedurepresented can be generally applied to predict the post-failure evolution of subaqueous landslides andfacilitates the extraction of the moving soil–water boundary, which can serve as source input fortsunami propagation modelling.ISSN:0016-8505ISSN:1751-765

A MPM framework for large deformation seismic response analysis

Landslides are often triggered by earthquakes and can cause immense damage due to large mass movements. To model such large-deformation events, the material point method (MPM) has become increasingly popular in recent years. A limitation of existing MPM implementations is the lack of appropriate boundary conditions to perform seismic response analysis of slopes. In this article, an extension to the basic MPM framework is proposed for simulating the seismic triggering and subsequent collapse of slopes within a single analysis step. Original implementations of a compliant base boundary and free-field boundary conditions in the MPM framework are presented, enabling the application of input ground motions while accounting for the absorption of outgoing waves and the free-ground movement at the lateral boundaries. An example slope is analysed to illustrate the proposed procedure and to benchmark it against the results obtained using an independent simulation technique, based on a three-step FE analysis. The comparison generally shows a good agreement of the results obtained from the two independent procedures and highlights advantages of the presented “all-in-one” MPM approach, in particular for long duration strong motions.ISSN:0008-3674ISSN:1208-601

Material point method for large deformation seismic response analysis

Landslides triggered by earthquakes are one of the major seismic hazards and can cause large damages and fatalities. The material point method (MPM) has become a popular technique to model such large mass movements. A limitation of existing MPM implementations is the lack of appropriate boundary conditions to perform seismic response analysis of slopes. To bridge this gap, an extension to the basic MPM framework is presented for simulating the seismic triggering and subsequent collapse of slopes within a single analysis step. The concepts of a compliant base boundary and free-field columns are applied within the MPM framework enabling the direct application of input ground motions and accounting for the absorption of outgoing waves

A MPM framework for large deformation seismic response analysis

Landslides are often triggered by earthquakes and can cause immense damage due to large mass movements. To model such large-deformation events, the material point method (MPM) has become increasingly popular in recent years. A limitation of existing MPM implementations is the lack of appropriate boundary conditions to perform seismic response analysis of slopes. In this article, an extension to the basic MPM framework is proposed for simulating the seismic triggering and subsequent collapse of slopes within a single analysis step. Original implementations of a compliant base boundary and free-field boundary conditions in the MPM framework are presented, enabling the application of input ground motions while accounting for the absorption of outgoing waves and the free-ground movement at the lateral boundaries. An example slope is analysed to illustrate the proposed procedure and to benchmark it against the results obtained using an independent simulation technique, based on a three-step FE analysis. The comparison generally shows a good agreement of the results obtained from the two independent procedures and highlights advantages of the presented “all-in-one” MPM approach, in particular for long duration strong motions.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Sedimentation as a control for large submarine landslides - mechanical modeling and analysis of the Santa Barbara basin

ISSN:2169-9313ISSN:0148-0227ISSN:2169-935

A multisurface kinematic hardening model for the behavior of clays under combined static and undrained cyclic loading

In dynamic geotechnical problems, soils are often subjected to a combination of sustained static and fast cyclic loading. Under such loading conditions, saturated and normally consolidated clays generally experience a build-up of excess pore water pressure along with a degradation of stiffness and strength. If the strength of the soil falls below the static stress demand, a self-driven failure is triggered. In this paper, a constitutive model is presented for the analysis of such problems, based on a general multisurface plasticity framework. The hardening behavior, the initial arrangement of the surfaces, and the nonassociated volumetric flow rule are defined to capture important aspects of cyclic clay behavior. This includes nonlinear hysteretic stress-strain behavior, the effect of anisotropic consolidation, and the generation of excess pore water pressure during undrained cyclic loading along with a degradation of stiffness and strength. The model requires nine independent parameters, which can be derived from standard laboratory tests. A customized experimental program has been performed to validate the model performance. The model predictions show a good agreement with test results from monotonic and cyclic undrained triaxial tests, in particular with respect to the strain-softening response and the number of loading cycles to failure. A procedure for a general stress-space implicit numerical implementation for undrained, total stress-based finite element analyses is presented, including the derivation of the consistent tangent operator. Finally, a simulation of the seismic response of a submarine slope is shown to illustrate a possible application of the presented model.ISSN:0363-9061ISSN:1096-985

Basin Sediments Geometry and Strength as Controls for Post-Failure Emplacement Style of Alpine Sub-Lacustrine Landslides

Predicting the evolution of underwater mass movements in their post-failure stage is vital for risk assessment of offshore structures and ensuring safety of coastal communities threatened by tsunami waves. In the absence of sedimentological and geotechnical data, variability of the post-failure behavior in a specific marine or lacustrine setting is often attributed to predisposition factors such as the slope height-drop and depth to the basal shear surface. In this paper, the contribution of other geometrical parameters such as the slope inclination and the relative thickness of the frontal basin sediments is investigated using a coupled Eulerian-Lagrangian finite element framework. An emphasis is given to the important role of the strength difference between the slope and frontal basin sediments. The suggested framework is first validated against the well-documented Zinnen slide in Lake Lucerne (Switzerland), successfully reproducing the post-failure geometry and capturing the main features observed in published seismic profiles. It is then applied in a parametric study to illustrate the decisive role of the frontal basin sediments in determining the post-failure geometry of underwater mass wasting in similar settings.ISSN:2169-9313ISSN:0148-0227ISSN:2169-935