Seismic uplift capacity of inclined strip anchors

2005 ◽  
Vol 42 (1) ◽  
pp. 263-271 ◽  
Author(s):  
Deepankar Choudhury ◽  
K S Subba Rao
Keyword(s):  
Limit Equilibrium ◽  
Ground Surface ◽  
Failure Surface ◽  
Friction Angle ◽  
Uplift Capacity ◽  
Principle Of Superposition ◽  
Seismic Acceleration ◽  
Acceleration Coefficient ◽  
Angle Of Internal Friction ◽  
Seismic Forces

Uplift capacities of inclined strip anchors in soil with a horizontal ground surface are obtained under seismic conditions. Limit equilibrium approaches with a logarithm-spiral failure surface and pseudostatic seismic forces are adopted in the analysis. The results are presented in the form of seismic uplift capacity factors as functions of anchor inclination, embedment ratio, angle of internal friction of the soil, and horizontal and vertical seismic acceleration coefficients. The uplift capacity factors are worked out separately for cohesion, surcharge, and density components. Use of the principle of superposition for calculating anchor uplift capacity is validated. The vertical seismic acceleration coefficient always reduces the uplift capacity, whereas the horizontal seismic acceleration coefficient reduces the uplift capacity in most cases. The roles of anchor embedment ratio, soil friction angle, and anchor inclination in determination of the seismic uplift capacity are also discussed. Comparisons of the proposed method with available theories in the seismic case are also presented. The present study gives the minimum seismic uplift capacity factors compared with the existing theory.Key words: seismic uplift capacity factors, inclined strip anchors, limit equilibrium, pseudostatic, c–ϕ soil.

GENERALIZED SOLUTION FOR SEISMIC UPLIFT CAPACITY OF STRIP ANCHORS USING PSEUDO-STATIC APPROACH

2007 ◽  
Vol 01 (04) ◽  
pp. 311-328 ◽  
Author(s):  
DEEPANKAR CHOUDHURY ◽  
K. S. SUBBA RAO
Keyword(s):  
Limit Equilibrium ◽  
Failure Surface ◽  
Friction Angle ◽  
Present Theory ◽  
Generalized Solutions ◽  
Unit Weight ◽  
Uplift Capacity ◽  
Principle Of Superposition ◽  
Seismic Acceleration ◽  
Acceleration Coefficient

Generalized solutions for uplift capacity of inclined shallow strip anchors embedded in general c–ϕ soils with inclined slope carrying a uniform surcharge is developed in this paper for seismic condition. The individual effects of unit weight, surcharge and cohesion components on the computation of uplift capacity of anchors are considered. Limit equilibrium method with logspiral failure surface is adopted in the analysis and the effects of seismic forces are considered as pseudo-static forces. The results have been presented in the form of seismic uplift capacity factors as functions of anchor inclination, ground inclination, embedment ratio, soil friction angle and seismic acceleration coefficients both in the horizontal and vertical directions. Both the seismic accelerations change significantly the uplift capacity of anchors. Effect of the vertical seismic acceleration coefficient has been found to always reduce the uplift capacity whereas the effect of horizontal seismic acceleration coefficient has been found to reduce the uplift capacity in most of the cases. Results are presented in graphical and tabular forms. Estimation of error while using the principle of superposition to compute the seismic uplift capacity is also conducted. A comparative study between the present theory and available results in literature shows the merits and requirement of the present analysis.

Pseudo-Static Analysis of Slope Considering Circular Rupture Surface

2014 ◽  
Vol 5 (2) ◽  
pp. 37-43 ◽  
Author(s):  
Sima Ghosh
Keyword(s):  
Factor Of Safety ◽  
Limit Equilibrium ◽  
Slope Angle ◽  
Failure Surface ◽  
Friction Angle ◽  
Equilibrium Analysis ◽  
Seismic Slope Stability ◽  
Slide Mass ◽  
Critical Circle ◽  
Seismic Forces

In this present paper, a circular failure surface passing through the toe is assumed for a homogeneous soil, and the Fellenius line is used to locate the centre of the most critical circle. Using limit equilibrium analysis under the influence of static forces such as weight of potential slide mass and surcharge along with the pseudo-static seismic forces are considered to obtain the factor of safety of the slopes. Factor of safety is found through the application of force equilibrium. The effects of variation of different parameters like slope angle (i), soil friction angle (F) and seismic acceleration coefficients both in the horizontal and vertical directions (kh and kv respectively) on the factor of safety are presented. Finally, the present results are compared to the existing solutions available in literature and found to give minimum values of factor of safety using the present approach for seismic slope stability analysis.

Seismic passive earth pressure coefficients for sands

2001 ◽  
Vol 38 (4) ◽  
pp. 876-881 ◽  
Author(s):  
Jyant Kumar
Keyword(s):  
Limit Equilibrium ◽  
Earth Pressure ◽  
Logarithmic Spiral ◽  
Failure Surface ◽  
Passive Earth Pressure ◽  
Pressure Coefficients ◽  
Straight Line ◽  
Earth Pressures ◽  
Planar Failure ◽  
Seismic Forces

By taking the failure surface as a combination of the arc of a logarithmic spiral and a straight line, passive earth pressure coefficients in the presence of horizontal pseudostatic earthquake body forces have been computed for an inclined wall placed against cohesionless backfill material. The presence of seismic forces induces a considerable reduction in the passive earth resistance. The reduction increases with an increase in the magnitude of the earthquake acceleration. The effect becomes more predominant for loose sands. The obtained results compared well with those reported in the literature using curved failure surfaces. However, the results available in the literature on the basis of a planar failure surface are found to predict comparatively higher passive resistance.Key words: earth pressures, earthquakes, limit equilibrium, plasticity, retaining walls, sands.

Active earth pressure in cohesive soils with an inclined ground surface

2000 ◽  
Vol 37 (1) ◽  
pp. 171-177 ◽  
Author(s):  
Nirmala Gnanapragasam
Keyword(s):  
Analytical Solution ◽  
Ground Surface ◽  
Earth Pressure ◽  
Failure Surface ◽  
Friction Angle ◽  
Active Earth Pressure ◽  
Overburden Pressure ◽  
Retaining Structure ◽  
Lateral Earth Pressure ◽  
Fixed Orientation

An analytical solution is developed to determine the active lateral earth pressure distribution on a retaining structure when it consists of a cohesive backfill (internal friction angle ϕ > 0, cohesion c > 0) with an inclined ground surface. The solution derived encompasses both Bell's equation (for cohesive or cohesionless backfill with a horizontal ground surface) and Rankine's solution (for cohesionless backfill with an inclined ground surface). The orientation of the failure surface is also determined. Results indicate that, unlike the soil-wall scenarios of Bell and Rankine where the failure planes are parallel with a fixed orientation independent of the overburden pressure, for sloping cohesive backfill (ϕ > 0, c > 0) the slope of the failure surface is a function of the overburden pressure and becomes shallower with depth, thus forming a curvilinear failure surface. The solution developed can also be used to check the sustainability of a slope. The analytical solution can be programmed conveniently in a computer.Key words: retaining structure, active earth pressure, cohesive backfill.

scholarly journals Analysis of passive earth pressure modification due to seepage flow effects

2018 ◽  
Vol 55 (5) ◽  
pp. 666-679 ◽  
Author(s):  
Z. Hu ◽  
Z.X. Yang ◽  
S.P. Wilkinson
Keyword(s):  
Limit Equilibrium ◽  
Retaining Wall ◽  
Reaction Force ◽  
Earth Pressure ◽  
Failure Surface ◽  
Friction Angle ◽  
Seepage Flow ◽  
Fourier Series Expansion ◽  
Passive Earth Pressure ◽  
Interface Friction

Using an assumed vertical retaining wall with a drainage system along the soil–structure interface, this paper analyses the effect of anisotropic seepage flow on the development of passive earth pressure. Extremely unfavourable seepage flow inside the backfill, perhaps due to heavy rainfall, will dramatically increase active earth pressure while reducing passive earth pressure, thus increasing the probability of instability of the retaining structure. A trial and error analysis based on limit equilibrium is applied to identify the optimum failure surface. The flow field is computed using Fourier series expansion, and the effective reaction force along the curved failure surface is obtained by solving a modified Kötter equation considering the effect of seepage flow. This approach correlates well with other existing results. For small values of both the internal friction angle and interface friction angle, the failure surface can be appropriately simplified with a planar approximation. A parametric study indicates that the degree of anisotropic seepage flow affects the resulting passive earth pressure. In addition, incremental increases in the effective friction angle and interface friction angle both lead to an increase in passive earth pressure.

Pseudo-Dynamic Bearing Capacity of Shallow Strip Footing Resting on c-Φ Soil Considering Composite Failure Surface

2015 ◽  
Vol 6 (2) ◽  
pp. 12-34 ◽  
Author(s):  
Arijit Saha ◽  
Sima Ghosh
Keyword(s):  
Bearing Capacity ◽  
Failure Mechanism ◽  
Limit Equilibrium ◽  
Failure Surface ◽  
Friction Angle ◽  
Strip Footing ◽  
Unit Weight ◽  
Composite Failure ◽  
Seismic Accelerations ◽  
Seismic Bearing Capacity

The evaluation of bearing capacity of shallow strip footing under seismic loading condition is an important phenomenon. This paper presents a pseudo-dynamic approach to evaluate the seismic bearing capacity of shallow strip footing resting on c-F soil using limit equilibrium method considering the composite failure mechanism. A single seismic bearing capacity coefficient (N?e) presents here for the simultaneous resistance of unit weight, surcharge and cohesion, which is more practical to simulate the failure mechanism. The effect of soil friction angle(F), soil cohesion(c), shear wave and primary wave velocity(Vs, Vp) and horizontal and vertical seismic accelerations(kh, kv) are taken into account to evaluate the seismic bearing capacity of foundation. The results obtained from the present analysis are presented in both tabular and graphical non-dimensional form. Results are thoroughly compared with the existing values in the literature and the significance of the present methodology for designing the shallow strip footing is discussed.

scholarly journals Calculation of Active Earth Pressure for Narrow Backfill with a Curved Slip Surface

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Zhihui Wang ◽  
Aixiang Wu ◽  
Yiming Wang
Keyword(s):  
Equilibrium Equation ◽  
Slip Surface ◽  
Limit Equilibrium ◽  
Retaining Wall ◽  
Earth Pressure ◽  
Failure Surface ◽  
Friction Angle ◽  
Force Balance ◽  
Vertical Force ◽  
The Earth

A method was proposed to calculate the earth pressure from a cohesionless backfill with a high aspect ratio (ratio of height to width of retaining wall). An exponential equation of slip surface was proposed first. The proposed nonlinear slip surface equation can be obtained once the width and height of the backfill as well as the internal friction angle of the backfill were given. The failure surface from the proposed formula agreed well with the experimental slip surface. Then, the earth pressure was calculated using a simplified equilibrium equation based on the proposed slip surface. It is assumed that the minor principal stress of the backfill near the wall and at its corresponding slip surface where the depth is the same is the same. Thus, based on the vertical force balance of the horizontal backfill strip, assuming the wall-soil interface and the slip surface is in the limit equilibrium state, defined by the Mohr–Coulomb criterion, the differential equilibrium equation was obtained and numerically solved. The calculated results agreed well with the test data from the published literature.

scholarly journals Ultimate Capacity Analysis and Determination of the Position of Failure Surface for Uplift Piles

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Qian Su ◽  
Xiaoxi Zhang ◽  
Pingbao Yin ◽  
Wenhui Zhao
Keyword(s):  
Limit Equilibrium ◽  
Failure Surface ◽  
Equilibrium Analysis ◽  
Soil Parameters ◽  
Uplift Capacity ◽  
Ultimate Capacity ◽  
Potential Failure ◽  
Coulomb Failure Criterion ◽  
Slice Method

Ultimate capacity and failure surface position of uplift piles are dependent on soil parameters. In this paper, the horizontal slice method is used to discuss the relation among the ultimate uplift capacity, the failure surface position, and soil parameters with Mohr-Coulomb failure criterion. According to the limit equilibrium analysis, the ultimate uplift capacity is calculated by dividing soil around the pile into slices with considering the potential failure surface as a group of several sectional planes. Then the multivariate function used to calculate ultimate capacity is established and optimized by the sequential quadratic programming. Through the numerical calculation and comparison with the previous research, the results show that the method is reasonable and effective and can be used to determine the failure surface and the magnitude of the ultimate capacity of uplift piles.

Limit equilibrium computation of dynamic passive earth pressure

1995 ◽  
Vol 32 (3) ◽  
pp. 481-487 ◽  
Author(s):  
Ernest E. Morrison Jr. ◽  
Robert M. Ebeling
Keyword(s):  
Limit Equilibrium ◽  
Pressure Coefficient ◽  
Earth Pressure ◽  
Failure Surface ◽  
Friction Angle ◽  
Passive Earth Pressure ◽  
Equilibrium Equations ◽  
Cohesionless Soils ◽  
Earth Pressures ◽  
Earth Pressure Coefficient

Few solution techniques exist for the determination of pseudostatic dynamic passive earth pressures for cohesionless soils. The widely accepted Mononobe–Okabe equation can result in the computing of unconservative values if the wall interface friction angle is greater than half the soil internal friction angle. As an alternate solution, equilibrium equations were formulated assuming a log spiral failure surface, and a research computer program was written to calculate the dynamic passive earth pressure coefficient. The primary purpose of this paper is to present a comparison of results obtained using the Mononobe–Okabe equation with those obtained using the log spiral formulation. Key words : pseudostatic, dynamic, passive earth pressure.

scholarly journals The Expression of Seismic Surrounding Rock Pressure for a Shallow Tunnel Is Derived Using the Pseudostatic Method

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Zhengde Wei ◽  
Yanpeng Zhu
Keyword(s):  
Rock Pressure ◽  
Limit Equilibrium ◽  
Seismic Loading ◽  
Surrounding Rock ◽  
Explicit Calculation ◽  
Shallow Tunnel ◽  
Seismic Acceleration ◽  
Acceleration Coefficient ◽  
Shallow Tunnels ◽  
Surrounding Rock Pressure

Terzaghi developed a generalized expression of the vertical surrounding rock pressures of shallow tunnels by considering the limit equilibrium of soil masses. In this paper, based on the Terzaghi failure mode, the pseudostatic method is used to derive this expression under seismic loading conditions. The surrounding rock in the fractured zone of the tunnel side wall is analyzed as an isolated body using the limit equilibrium method to obtain the explicit calculation expressions of the horizontal surrounding rock pressures of a shallow tunnel under seismic loading. Case analysis indicates that the proposed method is feasible. In addition, the influence of the seismic acceleration coefficient on surrounding rock pressures is further discussed. The results show that the horizontal surrounding rock pressure decreases with the increase of seismic acceleration coefficients. The vertical surrounding rock pressure increases as the horizontal seismic acceleration coefficient increases, and it decreases with the increase of the vertical seismic acceleration coefficient, and the effect of the seismic acceleration coefficient on surrounding rock pressure is significant. The study results can provide reference for the seismic safety evaluation and structural seismic design of shallow tunnels.

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