Slope stability analysis geotechnical design manual m 4603 chapter 74 december 2006 slope stability analysis detailed assessment of the groundwater regime within and beneath the slope is also critical. Conventional slope stability analysis is based on the assumption that slopes fail simultaneously along the. Pseudostatic seismic slope stability analysis, combined with the in. The piles used in slope stabilization are usually subjected to lateral force through. Pdf numerical modeling of submarine landslides with sensitive. Gisbased probabilistic slope stability assessment using. The fe results show that largescale catastrophic failure of submarine slopes might have occurred due to shear band propagation through strain softening clay layers, which cannot be explained using the traditional limit equilibrium methods for slope stability analysis.
Pdf a submarine landslide might be initiated from the steeper part of the seabed. The main objectives of slope stability analysis are finding endangered areas, investigation of potential failure mechanisms, determination of the slope sensitivity to different triggering mechanisms, designing of optimal slopes with regard to safety, reliability and economics, designing possible remedial measures, e. Geomorphological and slope stability analyses reveal that differences in. Progressive failure of offshore slopes due to construction. System sciences factors affecting seismic response of. The shear band propagation approach offers an alternative view, where an initial small failure can grow into a larger failure at the point of initiation. In the traditional deterministic approach to slope stability analysis and design, the shear strength, slope geometry, external loads, and pore water pressures are assigned specific unvarying values. Request permission export citation add to favorites track citation. A shear band is assumed to have formed if the addition of a perturbation to the homogeneous fields just before the peak stress is reached results in a localization of the shear strain.
Recently, by using a meshfree galerkin method, li et al. Comparing the consequences, the sliding planes and safety factors agreed well with. Finite element analysis of rock slope stability using. Analytical and numerical modeling of progressive failure. Slope stability analyses include static and dynamic, analytical or empirical methods to evaluate the stability of earth and rockfill dams. Apr 04, 2019 shear band propagation analysis of submarine slope stability. The stability analysis of underwater slopes based on strength. A nonlinear mathematical model for postpeak degradation of undrained shear strength of sensitive clay, applicable to small to largestrains, is proposed in this study based on available experimental results. Submarine landslidesstability analysis and risk assessment for. This consideration separates the shear band growth into progressive stable and catastrophic dynamic stages and treats the band growth as a true physical process rather than an. Analytical and numerical modeling of progressive failure of.
This may be because a 3d model is likely to introduce a much larger number of. The ability to predict the two different modes of postfailure landslide evolution is critical for determining the tsunami hazard and type of landslide impact on offshore structures. The stability analysis of underwater slopes based on. Symbol parameter dimensions f factor of safety against sliding along sheet joint calculated h height of the overall slope or of each bench 60 m or 20 m respectively. Mar 08, 2015 a simple approach to slope stability analysis has been developed through definition of the shear stress ratio and assessment of the energy balance conditions for sbp and arrest in a nonlinear submarine slope. Please note that this is an authorproduced pdf of an article accepted for. He is engaged in the constitutive modeling of geomaterials and the analysis of progressive and catastrophic failure in soils, with applications to creeping terrestrial and tsunamigenic submarine landslides.
Shear band propagation analysis of submarine slope stability. Puzrin has been full professor of geotechnical engineering at the eth zurich since 2004. Strength reduction stability geoslope international. Abstract when a region of intense shear in a slope is much thinner than other relevant geometric lengths, this shear failure may be approximated as localized slip, as in faulting, with strength determined by frictional properties of the sediment and effective stress normal to the failure surface.
The paper summarises recent developments in the shear band propagation approach, which enables simplified submarine slope stability analysis to account for catastrophic and progressive failure. The paper summarises recent developments in the shear band propagation approach, which enables simplified submarine slope stability analysis. Effects of the shear band propagation phenomenon on the evolution of submarine landslides and their hazards for costal communities and offshore infrastructure. This paper is based on strength reduction method, considering the deformation parameters of rock mass to discuss the stability of underwater slopes. Lee and edwards, 1986, reduces the earthquake acceleration time history to an equivalent inertial force acting statically on the potential slope wedge. The modified ring shear, direct shear, and triaxial compression apparatuses were used to investigate the fully softened shear strength using normally consolidated, remolded specimens. Homepage geomechanics chair of geotechnical engineering. Principles of construction on permanent landslides. For comparison the expected landslide thickness from an infinite slope analysis is also shown, which compares well with the failure mechanism resulting from the 2. The natural soils used in the residual and fully softened research have a range of liquid limit of 24 to 286%, plasticity index of 8 to 244%, and claysize. Stability analysis method for rock slope with an irregular. Rice abstract when a region of intense shear in a slope is much thinner than other relevant geometric lengths, this shear failure may be approximated as localized slip.
Present methods for stability analysis of underwater slopes are mostly confined to laboratory experiments and limit equilibrium method. Slopes need be designed and cut with a margin of safety for open pit mines. The purpose of this project was to investigate slope stability and shear strength in deep water. Transition from shear band propagation to global slab failure. The stability condition of slopes is a subject of study and research in soil mechanics, geotechnical engineering and engineering geology. Eventually, the shear band deviates toward the seafloor, resulting in a large, nonshallow, slope. In contrast to conventional slope stability analysis, which assumes that slopes fail simultaneously along their entire length, the shear band propagation approach is. Large landslides in both environments are generally progressive in nature. A simple approach to slope stability analysis of naturally occurring, mild nonlinear slopes is proposed through extension of shear band propagation sbp theory.
Initiation and mechanisms of catastrophic submarine landslides. The slope failure mechanisms are examined using the concept of shear band propagation. Submarine landslidesstability analysis and risk assessment for offshore. In contrast to conventional slope stability analysis, which assumes that slopes fail simultaneously along their entire length, the shear band propagation approach is capable of explaining the enormous dimensions of observed paleolandslides. Slope stability analysis by the limit equilibrium method. Based on the finite element software abaqus, the strength reduction method has been introduced to submarine slope stability evaluation. Submarine slope stability executive summary background and context oil and gas developments often require placing equipment, e. Effects of sedimentation and shearing on the triggering of. Sediment drift, submarine landslide, undrained shear strength, hemipelagite. By contrast, 3d analyses of slope stability are much less reported e. Shear band propagation is an effective mechanism to explain large. This approach covers a wide variety of potential failure mechanisms, such as slab failures, spreadings, ploughings and runouts, and provides analytical.
This paper extends shear band propagation analysis of slope failures to the investigation of ploughing and runout phenomena in submarine landslides. Final submission, 14 april 2009, for publication in proceedings, 4th international symposium on submarine mass movements and their consequences, austin, tx, 811 november 2009 1 modeling slope instability as shear rupture propagation in a saturated porous. Based on shear band propagation criteria, puzrin and his coworkers developed. There are some similarities and differences between failure mechanisms and potential causes of failure of slopes in these two environments. Based on the finite element software abaqus, the strength reduction method has been introduced to submarine. The future application of shear band propagation theory to submarine landslide analysis is also discussed. The limit equilibrium method is the most common approach for analyzing slope stability in both two and three dimensions. Rice 1,2 1school of engineering and applied sciences, 2department of earth and planetary sciences, harvard university, 29 oxford st. Sedimentation as a control for large submarine landslides. Jul 12, 2017 the factors, which mainly influence the stability of a typical openpit slope, are the shear strength parameters of slope forming material, the presence and characteristics of discontinuities in the slope mass and the groundwater conditions singh and monjezi 2000. Modeling slope instability as shear rupture propagation in a saturated porous medium robert c. For the shear band to propagate, the energy produced in the body by an incremental propagation of the shear band must exceed the energy required for the propagation. Shear strength for slope stability analysis slope stability. In strain softening soils, however, the le approach assumes that the failure takes place simultaneously along the entire sliding surface where the shear stress.
Shear strength reduction method ssr advantages and disadvantages of lem and ssr shear strength reduction outline applications soil models mse wall slope with supports 3d effect on slope stability analysis. Results show that the shear band propagation approach successfully predicts observed failure geometries and suggests triggering conditions from a lower magnitude seismic event compared to that predicted using limiting equilibrium. Pdf finite element modeling of progressive and retrogressive. Limit equilibrium analyses has been used for stability assessment of submarine slopes e. Landslides in both onshore and offshore environments are always a potential hazard and a great threat to many communities and infrastructure. Geophysical observations of palaeolandslides in offshore. Using shear strength reduction method for 2d and 3d slope. To backanalyze multiple sets of slope stability parameters simultaneously under uncertainty, the backanalysis can be implemented in a probabilistic way, in which uncertain parameters are modelled as random variables, and their distributions are improved based on the observed slope failure information. Submarine slope stability evaluation based on strength. Many factors have been proposed to cause underwater landslides, with longer acting conditioning factors priming the slope and shortterm, transient factors providing the final trigger see for a discussion. Submarine slope stability forecasting and back analyses in. Modeling slope instability as shear rupture propagation medium 219 and strain are designated as s f s xx, s zz, s xz and e.
The limit equilibrium method is the most common approach for analyzing slope stability in. Pdf transition from shear band propagation to global. Gigantic submarine landslides pose a significant threat to offshore infrastructures and may be initiated by an inconspicuous weakened zone, followed by catastrophic shear band propagation under the effect of strain softening. Submarine slope failures due to pipe structure formation. Much attention has been paid over the last two decades to unidirectional parallel to the travel direction of sliding mass shear band.
To backanalyze multiple sets of slope stability parameters simultaneously under uncertainty, the back analysis can be implemented in a probabilistic way, in which uncertain parameters are modelled as random variables, and their distributions are improved based on the observed slope failure information. With the same finite element model, the safety factors of the land slope and submarine slope are respectively 1. Lower limits of arrest length of the shear band and criteria for global slab failure are obtained for cases with heavy viscous damping, i. The presented method can obtain not only the detailed stability status at any grid node of a complex shear plane but also the global safety of the slope. Detailed pieziometric data at multiple locations and depths within and below the slope will likely be needed. Pdf effects of shear band propagation on submarine landslide. Appendix d discusses shear strength value selection. This approach covers a wide variety of potential failure mechanisms, such as slab failures, spreadings, ploughings and runouts, and provides analytical energy balance criteria for predicting their occurrence. Shear strength for slope stability analysis okiryu civilenvironmental op 30 may 17 14. Fundamentals and methods presents basic principles for the safe design of constructed or natural earth slopes. Innovative soil improvement exploring effects of pore fluid chemistry on enhanced delivery of soil improving agents and on soil conditioning for tunnel boring machines. A dynamic solution of the shear band propagation in. So, submarine slope stability evaluation is not only an important link of the construction safety guarantee and soil mechanics in the new field of ocean direction, but also the development of energy demand.
They were mostly based on an approach that flows naturally from the definition of slope factor of safety, and is now commonly referred to as the shear strength reduction ssr technique. Modeling slope instability as shear rupture propagation in a saturated porous medium r. An initial weak zone appears in the steepest part of the slope where the combined action of gravity and seismic loads overcomes the degraded peak shear resistance of the soil. Transition from shear band propagation to global slab failure in. Application of the shear band propagation approach to the gis based 3d slope stability analysis. So far the sbp approach has been mainly developed for a case of an infinite slope, an assumption which creates a significant limitation for the application to realworld landslides. Seismic behaviour of creeping landslides at the flanks of water reservoirs. Shear strength for slope stability analysis fattdad geotechnical 6 jun 17 11.
Transition from shear band propagation to global slab. Draft 3 the recently developed shear band propagation sbp approach for submarine slope stability analysis helps to overcome these limitations, by explaining how a relatively short initial slip surface localized shear zone of finite thickness, marked in red in figure 1 can under specific conditions propagate dynamically tens of. Economics could be improved by steepening the slope thereby reducing the amount of waste excavation. Slope stability refers to the condition of inclined soil or rock slopes to withstand or undergo movement. Submarine landslide can destroy various engineering facilities. Slope stability analysis by the limit equilibrium method books. Application of the shear band propagation method to slope.
Slope stability analysis with the shear strength reduction method we believe that the ssr method, facilitated by its implementation in software, is ready for prime time, the point at which it can be applied to the practical, routine analysis of slopes. Criteria for planar shear band propagation in submarine. Slope stability analysis using limit equilibrium method lem vs. Much attention has been paid over the last two decades to unidirectional parallel to the travel direction of sliding mass shear band propagation sbp related. Canadian geotechnical journal canadian science publishing. The aim of this paper is to verify the shear strength reduction technique for the finite element slope stability analysis. The effect of adding perturbations of different sizes. Submarine slope failures can occur in such areas and create soil slides. Shear band propagation analysis of submarine slope. Modeling slope instability as shear rupture propagation in a. Several technical issues have arisen in numerical simulations of dynamic shear band propagation. Finite element analysis of rock slope stability using shear. Once deformation takes place and the weak zone exceeds a critical length, a shear band may propagate into the adjacent slope and can initiate retrogressive slope failure fig.
Request pdf gisbased probabilistic slope stability assessment using shear band propagation this paper describes a gisbased application of shear band propagation to model slope instability. Landslide developed in rock mass usually has irregular shear plane. Conventional limiting equilibrium le analysis assumes that failure takes place. Shear band and landslide dynamics in submerged and. By definition, the factor of safety of a slope is the ratio of actual soil shear. An important orginal point in the proposed method is that the slope failure is defined according to the shear strain failure criterion. Work on this project was broken up into computational investigations of simple, hypothetical slopes and stratigraphies, and more complex, irregular slopes based on actual bathymetry from offshore surveys. An approach for calculating distributed factor of safety of the irregular shear plane was put forward in this paper. Significance of the actual nonlinear slope geometry for.
A result is that an explanation of the conditions leading to failure can be attributed to many submarine landslides. Dynamic shear band propagation and microstructure of. The shear band propagation sbp approach for submarine slope stability analysis helps to explain how a relatively short initial slip surface localized shear zone of finite thickness, marked in. The paper summarises recent developments in the shear band propagation approach, which enables simplified submarine slope stability. Probabilistic stability analyses of undrained slopes by 3d. Back analysis in soil slope stability linkedin slideshare. Application of the shear band propagation method to slope stability. Growth of a shear band is strongly dependent on the shape of the slope, seismic parameters and the strength of soil and less dependent on. Modeling slope instability as shear rupture propagation in. Drained shear strength of stiff clays for slope stability. Investigation of postfailure behavior of submarine landslides.
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