Investigation of Lateral Stress Relief on theStability of PHI = 0 DEG Slopes Using Laboratory, Fracture Mechanics, and Finite Element Method Approaches

Total stress analyses of purely cohesive cut slopes utilize the undrained shear strength for slope stability analyses. These slopes can have an in-situ lateral earth pressure that is greater than the vertical pressure. Excavations into these materials results in expansion of the slope face due to release of confining pressure. When strains exceed that which can be internally absorbed through elastic deformation, failure planes or cracks may develop at the toe of the slope. However, conventional limit equilibrium methods of slope stability analysis do not account for the in-situ stress conditions or the development of shear zones or cracks that occur from lateral stress relief. Progressive failure of the slope may occur if internal lateral stresses are large enough to cause stress concentrations in front of the advancing toe cracks. Finite element methods using substitution methods reveal two distinct shear cracks at the toe of slope consisting of a horizontal and an inclined failure plane while a tension zone develops in the backslope region. The formation and extension of the shear cracks are strongly dependent on ko and they can extend to approximately 1/4 of the slope height due to initial lateral stress relief. Classical limit equilibrium solutions regarding the critical slope height have been revised to account for lateral stress relief. Analyses indicate good agreement with published case histories and they reveal how the shear zones propagate to create progressive slope failure in stiff clay slopes under total stress analyses

Submarine slope failure offshore Uruguay - first results

New geophysical acquired during cruise M78 with RV “Meteor” in 2009 reveal a large-scale slope failure complex. Positioned between 1800 and 3300 m water depth, the slope failure affected an area of at least 1200 km2. The failure is hosted in contouritic deposits. The morphology of the up 70 m high headwalls is underlain by a deeper reflector which we interpret as detachment. Listric faults positioned upslope these headwalls root in this detachment and are precursor of future failure at this location. The detachment correlates with a regional BSR mapped by Uruguayan colleagues. Cores recovered from 3 transects across the failure complex confirm that the acoustic transparent units are debrites. Sedimentological evidence in accordance with hydro-acoustic data indicate that debrites deposited downslope this failure complex are recent features on the slope

Identifying Slope Failure Deposits from a Potentially Mixed Magnetic Susceptibility Signal in Gas Hydrate Bearing Regions

The marine gas hydrate stability zone (GHSZ) occurs in the slope environment along many active and passive continental margins. In this environment, slope failures are common and can occur near the shelf slope break, within submarine canyons, or on the flanks of bathymetric highs, resulting in a spectrum of slope failure deposits from landslides to turbidites. On the Cascadia margin, the GHSZ occurs within the bathymetric thrust ridges and slope basins of the accretionary wedge. Here, the ridges are composed of uplifted abyssal plain deposits associated with submarine fans and/or paleoslope basin deposits formed during the evolution of the accretionary wedge (Johnson et al., 2006; Torres et al., 2008). The adjoining slope basins contain the deposits from slope failure of the ridges. Both ridges and slope basins offshore Central Oregon and Vancouver Island were sampled by drilling during ODP Leg 204 and IODP Expedition 311, respectively (Figure 1). The recovered cores document the distribution and abundance of gas hydrate in these regions within a stratigraphy that is dominated by silt and sand turbidites, debris flows, and intervals of silty clay, separated by hemipelagic clay

Failure of slopes

The dynamic mechanism of slope failure is studied both experimentally and analytically to establish the spatial and temporal process of failure initiation and propagation during collapse of a natural or man-made slope. Model slopes, constructed of a brittle cemented sand material, are tested to collapse in a geotechnical centrifuge and the dynamics of failure recorded by motion picture film and mechanical detectors within the slope specimen. Shear failure is observed to initiate at the toe and propagate rapidly to the crest in the presence of crest tension cracking. A finite difference approach is taken to numerically solve the plane strain slope stability problem under gravity, based on unstable material behavior. Using a Lagrangian differencing scheme in space and explicit integration in time with dynamic relaxation, the numerical method finds the equilibrium state of the slope as the large-time limit of a dynamic problem with artificial parameters. The solution predicts localized shear failure zones which initiate at the slope toe and propagate to the slope crest in the manner and geometry observed in the centrifuge tests. In so doing, the finite difference algorithm also demonstrates an apparent ability to predict shear failure mechanisms in solid continua in general

Tow-Dimensional Simulation Analysis of Rock Slope Failure by DEM Using Bonding Force between Particles

As is known, there are many fractures in rock slope, and these fractures are often the cause of failure. Especially, the mechanism of toppling failure depends on fractures in rock slope. In this paper, two-dimensional simulation analysis and visualization for toppling failure of rock slope by distinct element method are carried out. In related with this simulation, the tensile stress of rock mass can be tried to be expressed by bonding theory. The rock slope model with this analysis can be freely setting the slope shape and the location of joints. Using this analytical model, it is tried to be simulated an actual toppling failure of rock slope. As the results of this analysis, it is recognized that this simulation can be expressed on this toppling failure phenomena. Moreover, the process of toppling failure can be visualized

Categorization of slope failure in southern Malaysia using total estimated hazard (TEHD) method

Slope is a measure of steepness or the degree of inclination of a feature relative to the horizontal plane. One of the phenomenon or incidents of a slope was called as slope failure or landslide. Slope failure was a major natural disaster that had affected the country in terms of injuries, deaths, property damage, destruction of services, public inconvenience and economic as well as financial losses. Slope failure cases were very serious geologic hazard disaster that happened in many countries around the world. The aim of this paper is to determine the category of slope failure in the state of Johor based on Landslide Hazard Zonation (LHZ). Data were calculated by using Total Estimated Hazard (TEHD) value method which considered six factors effecting the slope failure, including lithology; slope steepness, topography, land use class, annual rainfall and type of soil. Data on the factors were collected from Malaysia Public Works Department (JKR) inspection form, website, and secondary data resource. After that weight for each factor were identified by referring to Landslide Hazard Evaluation Factor (LHEF) rating scheme. Then determination of LHZ was done according to TEHD values which have five hazard zones; (1) very low; (2) low; (3) medium; (4) high; and (5) very high. The results of this study found that out of total fifty two cases there were three medium hazard (MH), twenty seven high hazard (HH) and twenty two very high hazard (VHH). Comparison between actual data from JKR and total 52 locations of slope failure in Johor showed that 94% accuracy, TEHD equation could calculate potential slope failure hazards in Johor very well

Numerical investigation into the failure of a micropile retaining wall

The paper presents a numerical investigation on the failure of a micropile wall that collapsed while excavating the adjacent ground. The main objectives are: to estimate the strength parameters of the ground; to perform a sensitivity analysis on the back slope height and to obtain the shape and position of the failure surface. Because of uncertainty of the original strength parameters, a simplified backanalysis using a range of cohesion/friction pairs has been used to estimate the most realistic strength parameters. The analysis shows that failure occurred because overestimation of strength and underestimation of loads.Peer ReviewedPostprint (author's final draft

Green Tax Reform and the Laffer curve in labour market models: A brief note

This paper shows that the dividing lines between the three possible outcome of a revenue-neutral ecological tax reform – double dividend, employment failure, environmental failure – can be ordered in terms of the slope of the wage curve and the slope of the Laffer curve in an efficiency wage model. A comparison of the efficiency wage model with bargaining models shows that the relation between the three outcomes and the slope of the Laffer curve is not the same but rather the opposite in the two models.environmental economics ;