The assessment of the safety factor with Probability Based Design and Euro code 7 in a slope stability case study

Slope stability accidents are widely spread in geotechnical calculation field.The purpose of this paper is to present an artificial slope stability case study,constructed in Porto Romano area (near Durres city, Albania). This embankment was foreseen to be building in a conic trunk shape, with diameter in base 43 m, height 10 m and inclination ratio 1:3, which was also used as a load during the consolidation process within the Preloading Mitigation Seismic Risk study of this area.The way of embankment's construction was suggested by the team of engineers, which performed the slope stability calculations during the design phase.Our study aims to deal with the recalculation of safety factor using Probability Based Design and Eurocode 7 Design Approaches after it failed at 6.45 m of height.After the recalculation we could estimate the causes that led to the failure

The Assessment Of Slopes Stability With Probability Methods

This paper aims to deal with the assessment of the stability of slopes, taking inconsideration several methods for analysis:- the limit equilibrium methods such as the Infinitive Slope method, Bishop's simplifiedmethod etc. upon which assumptions are made on the considered failure surface and theinternal forces interacting between the blocks, the equilibrium equations to be satisfied, theunknown variables to be determined (such as the safety factor and normal force) and the areaswithin which these methods could apply.- the probability methods in which the coefficient of variation of the factor of safety(COVF) is determined, (as the ratio of standard deviation to the mean coefficient of the safetyfactor, previously calculated), reliability R (as the probability of a certain case occurring in acertain way, at a certain time, in given conditions), the probability of failure Pf (as 1-R).Following the theoretical analysis, a number of numerical examples are included in order to illustrate in a more explicit manner the methodology used for the application of the assessment methods mentioned above, as well as to highlight the particularities and differences of each method

Random field failure and post-failure analyses of vertical slopes in soft clays

This research investigates the spatial heterogeneity of cohesion within soft clay and its implications for slope stability and post-failure analysis. In-situ cone penetration tests were conducted in alluvial soft clays to calibrate probabilistic strength properties. Slope stability analyses employed deterministic, semi-deterministic, and comprehensive probabilistic approaches, while post-failure analysis utilised the nodal integration-based particle finite element method. The undrained shear strength (cu) demonstrated a log-normal distribution (mean: 19 kPa, standard deviation: 3 kPa), with correlation lengths modeled through Bayesian inference. Treating correlation lengths as distributions resulted in a negligible 2% difference compared to using a single value for the probability of failure. Semi-deterministic analyses exhibited results similar to probabilistic analyses, offering computational advantages. Nevertheless, probabilistic analysis, considering spatial variability, provided more comprehensive insights for post-failure analysis. For a vertical slope of critical height in the studied soft clay, probabilistic analyses predicted a range of runout distances from 0 m to over 125 m. Specifically, 89% of these distances were less than 80 m, and 82% were less than 40 m. The findings contribute to an enhanced understanding of spatial variations in soil strength within soft clay slopes, providing valuable insights for future geotechnical assessments and design considerations

Stability assessment of a failed artificial embankment slope

This paper presents the stability problems of an artificial cohesion-less embankment slope supported on a saturated silty clay layer.In June 2011, an embankment about 9.00 m high started to be constructed in the Energetic Park of Porto Romano, in Durres city, Albania, as part of Preloading to Mitigate Seismic Risk project. The embankment, foreseen to be built in a conic trunk shape form, was to be used as a preload during the consolidation process of the site.Eighteen days after starting the construction process, when the embankment reached the height of 6.35 m, a soil stability failure of the embankment occurred. The calculations include the embankment slope stability analysis, during the design phase, considering the total height of the embankment (9.00 m) and at the moment of failure when the embankment height reached 6.35 m. The paper also presents the results of a back calculation of shear strength parameters at the moment of failure. Probability Based Design Method and Eurocode 7 Design Approaches are used during the analysis, considering long-term (drained) and short-term (undrained) conditions of the silty clay foundation

Random field failure and post-failure analyses of vertical slopes in soft clays

This research investigates the spatial heterogeneity of cohesion within soft clay and its implications for slope stability and post-failure analysis. In-situ cone penetration tests were conducted in alluvial soft clays to calibrate probabilistic strength properties. Slope stability analyses employed deterministic, semi-deterministic, and comprehensive probabilistic approaches, while post-failure analysis utilised the nodal integration-based particle finite element method. The undrained shear strength (cu) demonstrated a log-normal distribution (mean: 19 kPa, standard deviation: 3 kPa), with correlation lengths modeled through Bayesian inference. Treating correlation lengths as distributions resulted in a negligible 2% difference compared to using a single value for the probability of failure. Semi-deterministic analyses exhibited results similar to probabilistic analyses, offering computational advantages. Nevertheless, probabilistic analysis, considering spatial variability, provided more comprehensive insights for post-failure analysis. For a vertical slope of critical height in the studied soft clay, probabilistic analyses predicted a range of runout distances from 0 m to over 125 m. Specifically, 89% of these distances were less than 80 m, and 82% were less than 40 m. The findings contribute to an enhanced understanding of spatial variations in soil strength within soft clay slopes, providing valuable insights for future geotechnical assessments and design considerations

Spatial variability characteristics of the effective friction angle of Crag deposits and its effects on slope stability

This study investigated the spatial variability characteristics of the effective friction angle of Crag deposits which are granular soils occur in the east of England. Cone Penetration Test data were obtained at 26 locations and interpreted statistically. The distribution characteristic of the effective friction angle of Crag deposits was derived with the mean value, the standard deviation and the correlation length calibrated. Illustrations were also shown on how factors such as ground water pressures and the existence of soft/organic soil zones affect the measurement of the autocovariance function and thus the correlation length. Bayesian inference technique was adopted alongside the method of moments to determine the correlation length. Based on the obtained statistical parameters, both semi-deterministic (based on standard geotechnical design codes) and probabilistic finite element limit analyses were carried out to investigate the stability of slopes in Crag deposits. Slopes of various inclined angles were considered and comparisons between the semi-deterministic and probabilistic results were conducted to improve the understanding of the stability of Crag slopes and to provide insight into the slope stability code used in practice