scholarly journals Reliability Analysis of Layered Soil Slopes Considering Different Spatial Autocorrelation Structures

2020 ◽  
Vol 10 (11) ◽  
pp. 4029 ◽  
Author(s):  
Shaohe Zhang ◽  
Yuehua Li ◽  
Jingze Li ◽  
Leilei Liu
Keyword(s):  
Soil Properties ◽  
Reliability Analysis ◽  
Classical Model ◽  
Soil Heterogeneity ◽  
Layered Soil ◽  
Soil Layers ◽  
Scale Of Fluctuation ◽  
Soil Slopes ◽  
Smoothness Parameter ◽  
Parametric Studies

It is widely recognized that different geological formations often vary differently in space. Therefore, soil properties from different layers should be modeled by different autocorrelation functions (ACFs) to reflect such soil heterogeneity. However, the same ACFs are frequently used for different soil layers in slope reliability analysis for simplicity purpose in the literature. The present work is a study on the effects of ACFs on the reliability analysis of layered soil slopes, where the soil properties of different layers are considered by different ACFs. Five commonly used classical ACFs and the non-classical Whittle–Matérn model were investigated in this study. Cholesky decomposition and Monte Carlo simulation were used to simulate the spatial variability of the soil properties and estimate the probability of failure (Pf) of slopes, respectively. Illustrative examples with various parametric studies show that when the soil properties from different layers are characterized by the same ACFs, the Pf of the studied slopes is comparable with that estimated using different ACFs for different soil layers. This indicates that the type of ACF has only a small impact on the slope reliability assessment. However, the Pf may be underestimated by the single exponential ACF and overestimated by the cosine exponential ACF. The scale of fluctuation of the soil properties influences the slope reliability more than the ACFs. In addition, the smoothness parameter in the non-classical model has a significant influence on the reliability of the slope, where Pf increases with the increase of the smoothness parameter.

Estimation of Scale of Fluctuation of Soil Properties Indexes

2012 ◽  
Vol 256-259 ◽  
pp. 149-152
Author(s):  
Shu Wang Yan ◽  
Lin Ping Guo
Keyword(s):  
Risk Assessment ◽  
Soil Properties ◽  
Reliability Analysis ◽  
Convenient Method ◽  
Geotechnical Engineering ◽  
Vertical Direction ◽  
Comparison Of Methods ◽  
Correlation Distance ◽  
Scale Of Fluctuation ◽  
High Application

By summarizing and comparison of methods for evaluating the scale of fluctuation, suitable and convenient method to calculate correlation distance is obtained. The space averaged method is employed to analyze the scale of fluctuation of soil in the vertical direction of Tianjin combining geology data, and regional representative values are obtained, which is of high application value on risk assessment and reliability analysis in geotechnical engineering.

scholarly journals Probabilistic Bearing Capacity of a Pavement Resting on Fibre Reinforced Embankment Considering Soil Spatial Variability

2021 ◽  
Vol 7 ◽  
Author(s):  
Kouseya Choudhuri ◽  
Debarghya Chakraborty
Keyword(s):  
Spatial Variability ◽  
Soil Properties ◽  
Bearing Capacity ◽  
Coefficient Of Variation ◽  
Friction Angle ◽  
Horizontal Scale ◽  
Vertical Scale ◽  
Scale Of Fluctuation ◽  
The Mean ◽  
The Finite Difference Method

This paper intends to examine the influence of spatial variability of soil properties on the probabilistic bearing capacity of a pavement located on the crest of a fibre reinforced embankment. An anisotropic random field, in combination with the finite difference method, is used to carry out the probabilistic analyses. The cohesion and internal friction angle of the soil are assumed to be lognormally distributed. The Monte Carlo simulations are carried out to obtain the mean and coefficient of variation of the pavement bearing capacity. The mean bearing capacity of the pavement is found to decrease with the increase in horizontal scale of fluctuation for a constant vertical scale of fluctuation; whereas, the coefficient of variation of the bearing capacity increases with the increase in horizontal scale of fluctuation. However, both the mean and coefficient of variation of bearing capacity of the pavement are observed to be increasing with the increase in vertical scale of fluctuation for a constant horizontal scale of fluctuation. Apart from the different scales of fluctuation, the effects of out of the plane length of the embankment and randomness in soil properties on the probabilistic bearing capacity are also investigated in the present study.

Fatigue Safety Factors for Flexible Risers Based on Case Specific Reliability Analysis

2005 ◽  
Author(s):  
Bernt J. Leira ◽  
Ragnar T. Igland ◽  
Gro S. Baarholm ◽  
Knut A. Farnes ◽  
Dick Percy
Keyword(s):  
Reliability Analysis ◽  
Limit State ◽  
State Function ◽  
Safety Factors ◽  
Fatigue Lifetime ◽  
Statistical Variation ◽  
Parametric Studies ◽  
Flexible Risers ◽  
Corrosive Environments ◽  
Wave Induced

In the present paper, fatigue safety factors for flexible risers are assessed. A procedure for reliability analysis of wave-induced fatigue is first described. The procedure is based on performing a number of parametric studies with respect to variables that influence the fatigue lifetime. The results of these parametric studies are subsequently combined with models describing the statistical scatter of the same parameters. By application of this procedure, the safety factors which are required in order to reach specific target reliability levels can be computed. Such safety factors are computed for three specific flexible riser configurations. Different SN -curves which correspond to different corrosive environments are considered. The percentwise contribution from each parameter to the total statistical variation of the limit state function is also quantified.

Influence of cross correlation between soil parameters on probability of failure of simple cohesive and c-ϕ slopes

2016 ◽  
Vol 53 (5) ◽  
pp. 839-853 ◽  
Author(s):  
Sina Javankhoshdel ◽  
Richard J. Bathurst
Keyword(s):  
Slope Stability ◽  
Soil Properties ◽  
Cross Correlation ◽  
Friction Angle ◽  
Probability Of Failure ◽  
Unit Weight ◽  
Soil Parameters ◽  
Design Charts ◽  
Soil Slopes ◽  
Cross Correlations

This paper focuses on the calculation of probability of failure of simple unreinforced slopes and the influence of the magnitude of cross correlation between soil parameters on numerical outcomes. A general closed-form solution for cohesive slopes with cross correlation between cohesion and unit weight was investigated and results compared with cases without cross correlation. Negative cross correlations between cohesion and friction angle and positive cross correlations between cohesion and unit weight, and friction angle and unit weight were considered in the current study. The factors of safety and probabilities of failure for the slopes with uncorrelated soil properties were obtained using probabilistic slope stability design charts previously reported by the writers. Results for cohesive soil slopes and positive cross correlation between cohesion and unit weight are shown to decrease probability of failure. Probability of failure also decreased for increasing negative cross correlation between cohesion and friction angle, and increasing positive correlation between cohesion and unit weight, and friction angle and unit weight. Probabilistic slope stability design charts presented by the writers in an earlier publication are extended to include cohesive-frictional (c-[Formula: see text]) soil slopes with and without cross correlation between soil input parameters. An important outcome of the work presented here is that cross correlation between random values of soil properties can reduce the probability of failure for simple slope cases. Hence, previous probabilistic design charts by the writers for simple soil slopes with uncorrelated soil properties are conservative (safe) for design. This study also provides one explanation why slope stability analyses using uncorrelated soil properties can predict unreasonably high probabilities of failure when conventional estimates of factor of safety suggest a stable slope.

scholarly journals Effect of Vertical Pressure on Horizontal and Vertical Permeability of Soil and Effect of Surcharge Pressure on 3D Consolidation of Soil

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Arpan Laskar ◽  
Sujit Kumar Pal
Keyword(s):  
Soil Properties ◽  
Three Dimensional ◽  
Vertical Pressure ◽  
Soil Layers ◽  
One Dimensional ◽  
Consolidation Theory ◽  
Vertical Permeability ◽  
Homogeneous Soil ◽  
Soil Changes

Permeability and consolidation of soil are known as the most variable soil properties. The values of permeability and consolidation of soil may vary with depth even in case of homogeneous soil layers, and because of that, the determination of appropriate values of permeability and consolidation is a complex and complicated engineering task. In this study, horizontal and vertical permeability apparatus and a 3D (three-dimensional) consolidation apparatus are developed to determine the effects of vertical pressure on horizontal and vertical permeability and the effects of vertical surcharge pressures on three-dimensional consolidation of soil. A series of horizontal and vertical permeability tests of soil under different vertical pressures and a series of 3D consolidation tests under different surcharge pressures are performed. From the study, it is observed that the horizontal and vertical permeability of soil changes with the changes in vertical pressures, and 3D consolidation of soil also changes with the changes in surcharge pressures. The horizontal and vertical permeability values obtained from the newly developed horizontal and vertical permeability apparatus are used in Terzaghi’s one-dimensional consolidation theory to find out the consolidation characteristics of the soil, and it is compared with the results obtained from the newly developed 3D consolidation apparatus.

Offshore Pile Foundation Subjected to Lateral Cyclic Load in Layered Soil

2014 ◽  
Vol 891-892 ◽  
pp. 24-29 ◽  
Author(s):  
Sudip Basack ◽  
Abhik Kumar Banerjee
Keyword(s):  
Numerical Model ◽  
Pile Foundation ◽  
Loading Condition ◽  
Cyclic Load ◽  
Complex Loading ◽  
Offshore Structures ◽  
Layered Soil ◽  
Interactive Performance ◽  
Parametric Studies ◽  
Combined Action

The pile foundations supporting offshore structures are required to be designed against cyclic load, moments and torques initiated by a combined action of waves, wind, tides, currents, etc. Such a complex loading condition produces progressive degradation in the pile-soil interactive performance which is likely to introduce significant reduction in bearing capacity with increased settlement and displacements. This paper is based on a numerical model developed by the Authors to study the response of pile foundation under lateral cyclic load in layered soil. The model is validated with a field test data and thereafter, parametric studies have been carried out. A brief description of the works conducted and the major conclusions drawn are highlighted in this paper.

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