scholarly journals АCCOUNTING THE SEISMIC COMPONENT OF THE LATERAL PRESSURE OF AN HETEROGENEOUS ANISOTROPIC SOIL ON MASSIVE HYDROTECHNICAL STRUCTURES

2020 ◽  
pp. 132-139
Author(s):  
I.V. Voytenko ◽  
Keyword(s):  
Horizontal Plane ◽  
Lateral Pressure ◽  
Friction Angle ◽  
Seismic Effect ◽  
Surface Load ◽  
Strength Anisotropy ◽  
Soil Medium ◽  
Active Pressure ◽  
Seismic Force ◽  
Anisotropic Soil

Abstract. Strength anisotropy is characteristic of layered soil bases and has been confirmed by numerous tests. The relevance and novelty of this research is to study the effect of the seismic factor on the active pressure of the friable soil medium having strength anisotropy. A numerical experiment was carried out using a specially developed computer program, the algorithm of which used the method for determining the lateral pressure of a heterogeneous anisotropic soil, taking into account the seismic effect. The proposed method is based on the solutions of the classical theory of Coulomb, the seismic component is taken into account on the basis of the static theory of the earthquake stability of structures. We considered a vertically ideally smooth wall in contact with a two-layer incoherent soil medium, the anisotropy of the strength properties of which is represented by hodographs of friction angle. The layers are parallel, no surface load. A numerical research was to determine the parameters of the active pressure of the soil of the lower layer during rotation of the hodograph of friction angle with steps of 300. We used 4 hodographs: 1) φ1=150-200; 2) φ2=200-250; 3) φ3=250-300; 4) φ4=300-350 with a horizontal plane of isotropy. Seismic impact was taken into account by the seismicity coefficient, taken equal to depending on the scale 0.025 (7), 0.05 (8), 0.1 (9). The horizontal orientation of the seismic force and with an angle of 200 to the horizontal plane was set. The obtained results make it possible to evaluate the seismic effect on the lateral pressure of anisotropic soil by comparing it with the corresponding indicators obtained earlier without taking into account the seismic factor. An analysis of computer solutions indicates the increase of the active pressure in seismic conditions by 14%-45% compared with the same indicator, which was determined without taking into account the seismic factor.

Research on Structure Security of a Spherical Tank Under Wind and Seismic Effect

2012 ◽  
Author(s):  
Xiang Li ◽  
Zhiwei Chen ◽  
Weihua Wang ◽  
Weike Jing ◽  
Shanshan Shao
Keyword(s):  
Safety Assessment ◽  
Failure Modes ◽  
Seismic Effect ◽  
Wind Loads ◽  
Foundation Settlement ◽  
Element Analysis ◽  
Structure Damage ◽  
Spherical Tank ◽  
Earthquake Force ◽  
Seismic Force

In the condition of the earthquake force and wind loads, there are many failure modes for the spherical tanks, such as the structure damage of the supports, uniform foundation settlement, displacement or upset, and the fracture of pipelines attached to the tank, etc. In this paper, more precise stress distribution of spherical tanks under wind loads and seismic force was obtained by finite element analysis. The safety assessment is carried out on a spherical tank. The weakness components of the spherical tank were found and the wind-proof performance and earthquake-proof performance of the spherical tanks could be improved.

CONSOLIDATION OF A CROSS-ANISOTROPIC SOIL MEDIUM

1984 ◽  
Vol 37 (3) ◽  
pp. 479-495 ◽  
Author(s):  
J. R. BOOKER ◽  
M. F. RANDOLPH
Keyword(s):  
Soil Medium ◽  
Anisotropic Soil

Influence of Anisotropic Internal Friction Angle on the Stability of Uniform Soil Slopes

2012 ◽  
Vol 170-173 ◽  
pp. 270-273 ◽  
Author(s):  
Lian Wei Zhang
Keyword(s):  
Slip Surface ◽  
Friction Angle ◽  
Soil Slope ◽  
Critical Slip Surface ◽  
Obvious Effect ◽  
Anisotropic Friction ◽  
Change Of Direction ◽  
Soil Slopes ◽  
Anisotropic Soil ◽  
The Stability

The effect of anisotropy of friction angle in natural deposited soil on the stability of soil slopes was studied in this paper. Stability analysis was performed on a uniform soil slope with anisotropic friction angle. Spencer’s method was used, and the variation of friction angle was assumed to be linear to the change of direction of the slip surface. It was shown that 7-10 percent of change in safety factor might achieve within a 10m-highed anisotropic soil slope. It was also found from the analysis that that frictional anisotropy had no obvious effect on the location of critical slip surface.

Effects of undrained strength anisotropy on surface subsidences induced by the construction of shallow tunnels

1989 ◽  
Vol 26 (2) ◽  
pp. 279-291 ◽  
Author(s):  
K. M. Lee ◽  
R. K. Rowe
Keyword(s):  
Finite Element ◽  
Deformation Behaviour ◽  
Strength Anisotropy ◽  
Element Analysis ◽  
Soft Clays ◽  
Soil Model ◽  
Undrained Strength ◽  
Anisotropic Soil ◽  
Gap Parameter ◽  
Surface Subsidences

The implementation of an anisotropic soil model that allows consideration of the variation of undrained strength due to anisotropy is described. This analysis is then used to identify the significance of strength anisotropy on the prediction of deformation behaviour of a shallow tunnel. It is found that, for the case of an unlined tunnel, attention should be given to the effect of strength anisotropy particularly for a soil possessing type "K" anisotropy (i.e., where the smallest undrained strength occurs at an angle θ other than the vertical or the horizontal, and the smallest value usually occurs at θ = 45°). On the other hand, for a lined tunnel, the effect of strength anisotropy upon the surface settlement profile will depend upon the size of a so-called "gap" parameter. The gap represents the net effect of loss of ground and some "workmanship" factors in a plane strain finite element analysis. Increasing the gap eases the restrictions imposed by the tunnel lining upon possible soil deformations, thereby increasing the effect of strength anisotropy. However, it is shown that for a lined tunnel with a moderate value of gap, detailed consideration of strength anisotropy may not be necessary. Key words: strength anisotropy, tunnelling, predictions, surface subsidences, finite element method, soil model, soft clays, vane strength.

scholarly journals Metamodel-Based Slope Reliability Analysis—Case of Spatially Variable Soils Considering a Rotated Anisotropy

Geosciences ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 465
Author(s):  
Tingting Zhang ◽  
Xiangfeng Guo ◽  
Julien Baroth ◽  
Daniel Dias
Keyword(s):  
Coefficient Of Variation ◽  
Cross Correlation ◽  
Friction Angle ◽  
Strength Properties ◽  
Deterministic Models ◽  
Sparse Polynomial ◽  
Model Combining ◽  
Sensitivity Indices ◽  
Anisotropic Soil ◽  
Autocorrelation Length

A rotation of the anisotropic soil fabric pattern is commonly observed in natural slopes with a tilted stratification. This study investigates the rotated anisotropy effects on slope reliability considering spatially varied soils. Karhunen–Loève expansion is used to generate the random fields of the soil shear strength properties (i.e., cohesion and friction angle). The presented probabilistic analyses are based on a meta-model combining Sparse Polynomial Chaos Expansion (SPCE) and Global Sensitivity Analysis (GSA). This method allows the number of involved random variables to be reduced and then the computational efficiency to be improved. Two kinds of deterministic models, namely a discretization kinematic approach and a finite element limit analysis, are considered. A variety of valuable results (i.e., failure probability, probability density function, statistical moments of model response, and sensitivity indices of input variables) can be effectively provided. Moreover, the influences of the rotated anisotropy, autocorrelation length, coefficient of variation and cross-correlation between the cohesion and friction angle on the probabilistic analysis results are discussed. The rotation of the anisotropic soil stratification has a significant effect on the slope stability, particularly for the cases with large values of autocorrelation length, coefficient of variation, and cross-correlation coefficient.

Interpretation of field vane strength of an anisotropic soil

1992 ◽  
Vol 29 (4) ◽  
pp. 627-637
Author(s):  
Vinod K. Garga ◽  
Mahbubul A. Khan
Keyword(s):  
Shear Strength ◽  
Undrained Shear Strength ◽  
Triaxial Tests ◽  
Strength Anisotropy ◽  
Shear Tests ◽  
Direct Shear Tests ◽  
State Of Stress ◽  
Anisotropic Soil ◽  
Undrained Shear

Determination of the undrained shear strength (Su) of overconsolidated soils such as the weathered clay crust overlying Leda clay is important for the design of shallow foundations and embankments. In situ vane shear tests and isotropically consolidated undrained triaxial tests have been conventionally used for this purpose. Contrasting test results from these two methods, low Su obtained from triaxial tests and high Su obtained from in situ vane shear tests, motivated further research into this problem. Strength anisotropy, due to in situ anisotropic state of stress and orientation of soil fabric during deposition, is believed to be the reason for these contrasting results. Improved testing and interpretation techniques for this type of anisotropic soil have been proposed. Weathered crusts are generally heavily over-consolidated, with K0 values greater than unity. Undrained triaxial shear tests conducted to date by various researchers are either isotropically consolidated or are anisotropically consolidated assuming K0 smaller than unity. Neither of these two methods represents the in situ state of stress of a clay crust. Therefore, in this investigation, the undisturbed samples were reconsolidated anisotropically to the in situ state of stress (K0 > 1) before shearing undrained in the triaxial test. Direct shear tests on horizontal and vertical specimens consolidated to normal stresses equal to σvo′ and σho′, respectively, were also conducted to investigate the strength anisotropy. Field vane tests have been reinterpreted in terms of this strength anisotropy. The undrained shear strength on top and bottom horizontal planes (Suh) obtained from these field vane tests within the crust provided comparable results with those from laboratory triaxial and direct shear tests which were reconsolidated to in situ stresses. Key words : in situ vane test, undrained shear strength, strength anisotropy, rate effect, anisotropic in situ state, weathered clay crust, overconsolidation.

Evaluating stability of anisotropically deposited soil slopes

2019 ◽  
Vol 56 (5) ◽  
pp. 753-760 ◽  
Author(s):  
H. Zhu ◽  
L.M. Zhang ◽  
T. Xiao
Keyword(s):  
Friction Angle ◽  
Probability Of Failure ◽  
Strength Properties ◽  
Lower Probability ◽  
Safety Level ◽  
Soil Fabric ◽  
Independent Case ◽  
Anisotropic Soil ◽  
Unfavorable Condition ◽  
Spatially Varying

Natural soils often exhibit an anisotropic fabric pattern as a result of soil deposition, weathering or filling. This study aims to investigate the effects of spatially variable anisotropic soil fabric in a slope on its safety factor and failure mechanisms, and to identify the critical fabric orientation that is most unfavorable to the slope stability. The strength properties of colluvium (i.e., cohesion and friction angle) are modeled as random fields under two conditions (i.e., independent and negatively correlated). The study reveals that there exists a critical fabric orientation at 30° at which the mean factor of safety is the lowest and the probability of failure is the highest. The negative cross-correlation between soil shear strength properties leads to a significantly lower probability of failure, compared to the independent case. The highest proportion of deep failure mechanism is also identified at the same fabric orientation of 30°. The identified critical fabric orientation is gentler than the slope inclination. This study suggests that the conventional understanding that stratification parallel to the slope surface appears to be the most unfavorable condition leading to the lowest safety level does not hold for spatially varying soils.

scholarly journals Design Diagrams for the Analysis of Active Pressure on Retaining Walls with the Effect of Line Surcharge

2017 ◽  
Vol 2017 ◽  
pp. 1-9
Author(s):  
Mojtaba Ahmadabadi ◽  
Mohammad Karim Faghirizadeh
Keyword(s):  
Pressure Distribution ◽  
Lateral Pressure ◽  
Limit Equilibrium ◽  
Pressure Coefficient ◽  
Failure Surface ◽  
Retaining Walls ◽  
Software Environment ◽  
Active Pressure ◽  
Failure Wedge ◽  
Different Soils

In this study, a formulation has been proposed to calculate the pressure on wall and determine the angle of failure wedge based on limit equilibrium method. The mentioned formulation is capable of calculating active pressure coefficient, culmination of forces in failure surface, and pressure distribution on wall with the effect of line surcharge. In addition, based on the proposed method, a simple formula has been proposed to calculate the angle of failure wedge by the effect of surcharge. Moreover, the proposed approach has the advantage of taking into account the effect of surcharge on elastoplastic environment by considering the parameters of soil and determining the extent to which the surcharge is effective in pressure distribution on the wall. However, in most previous methods and specifications, resultant lateral pressure from surcharge in elastic environment had been considered. Finally, based on the obtained results, the design diagrams for different soils and different surcharges have been proposed. According to these diagrams, pressure on wall, pressure distribution on wall, and angle of failure wedge will easily be achieved. Also, a computer program has been written in MATLAB software environment. Using the results of these codes, the pressure on wall with the effect of surcharge, the angle of failure wedge, and pressure distribution on wall will be determined.

The effect of the bending rigidity of a wall on lateral pressure distribution

1999 ◽  
Vol 36 (6) ◽  
pp. 1039-1055 ◽  
Author(s):  
Ching-Chuan Huang ◽  
Farn-Yue Menq ◽  
Yue-Chin Chou
Keyword(s):  
Pressure Distribution ◽  
Lateral Pressure ◽  
Retaining Wall ◽  
Friction Angle ◽  
Shear Stresses ◽  
Bending Rigidity ◽  
Half Height ◽  
The Moment ◽  
Wall System ◽  
Normal And Shear Stresses

A two-dimensional model retaining wall system was developed to investigate the effect of the bending rigidity of a wall, supported at the top and bottom, on the lateral pressure distribution at completion-of-backfilling condition. A total of 120 000 pieces of 1.96 mm diameter stainless steel rods were placed piece by piece behind the 500 mm high walls in a parallel and dense stack. Ten two-component load cells were mounted to the inner face of the wall to obtain simultaneously normal and shear stresses acting on the wall. The stress-deformation characteristics of the steel-rod assembly and the friction angle between the steel rods and the stainless plate were investigated thoroughly to provide parameters of the backfill material used. Four types of walls with different bending rigidities were employed. The deflections at the half-height of the wall at the moment of completion of backfill ranged between 0.03 and 4.6 mm. A parameter Rr, the relative degree of deflection at the half-height of the wall, was used to evaluate the lateral pressure distribution on the walls for their at-completion conditions. Both the lateral pressure coefficients and the patterns of lateral pressure distribution on the walls were strongly related to Rr .

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