Soil Wall Friction Angle Research Articles

Seismic active earth pressure for 3D earth retaining structure following a nonlinear failure criterion

Stability analysis for three-dimensional (3D) earth retaining structures (ERSs) is a pivotal problem in geotechnical engineering, particularly for seismically active areas. In this work, the 3D ERSs in soil are assessed for seismic stability following a nonlinear strength criterion. The power-law strength criterion and seismic forces are introduced into the 3D ERS stability analysis via a multi-cone failure mechanism. The coefficient of active soil pressure Ka is derived by exploiting the energy balance equation. The upper bound solutions, that is the maximum results of the Ka are captured with the help of a genetic algorithm. The validity of the current study is verified by a comparative analysis, and the effects of soil strength nonlinearity, the seismic forces, the soil-wall friction angle, the height, the inclined angle and the 3D geometric traits of ERSs on the Ka solutions and the stability of ERSs are investigated. It is indicated that the height and the 3D geometric characteristics of the ERSs will not only determine the Ka solutions directly, but also influence the impact of soil strength nonlinearity on the stability of ERSs. Strength criteria should be chosen combining the geometric characteristics of ERSs to derive more critical estimates on the stability of 3D ERSs. Additionally, a range of seismic and static stability charts used for preliminary design are put forward as well.

Impact of wall movements on the location of passive Earth thrust

Abstract The general assumption of linear variation of earth pressures with depth on retaining structures is still controversial; investigations are yet required to determine those distributions of the passive earth pressure (PEP) accurately and deduce the corresponding centroid location. In particular, for rigid retaining walls, the calculation of PEP is strongly dependent on the type of wall movement. This paper presents a numerical analysis for studying the influence of wall movement on the PEP distribution on a rigid retaining wall and the passive earth thrust location. The numerical predictions are remarkably similar to existing experimental works as recorded on scaled test models and full-scale retaining walls. It is observed that the PEP varies linearly with depth for the horizontal translation, but it is nonlinear when the movement is rotational about the top of the retaining wall. When rotation is around the top of the wall, the resultant of PEP is located at a depth that varies between 0.164 and 0.259H of the wall height measured from the base of the wall, which is lesser than 1/3 of the wall height. The passive earth thrust location is highly affected by the soil–wall friction angle, especially when the friction angle of the backfill material increases. Despite the herein presented results, further experiments are recommended to assess the corresponding numerical predictions.

Effect of Soil–Wall Friction Angle on Behaviour of Sheet Pile Wall Under Surcharge Loading

In this study, a solution is derived in the framework of the limit equilibrium approach for the design of cantilever sheet pile walls under both static and seismic conditions in cohesionless soil with uniform surcharge load located at the top of the wall. The proposed method satisfies the horizontal force equilibrium and moment equilibrium about toe simultaneously. From the results of the study, it is highlighted that the application of surcharge load increases the magnitude of bending moment along the depth of the sheet pile wall and deflection at the top of the wall. Further, the increase in plastic zone due to mobilisation of earth pressure is also observed. A parametric study is done by varying the soil–wall friction angle and magnitude of uniform surcharge load acting on the backfill of the cantilever sheet pile walls. From the results, it is observed that as the soil–wall friction angle increases, the maximum bending moment, deflection, depth of plastic zone and settlement adjacent to sheet pile wall decrease. Further, the increase in the magnitude of uniform surcharge increases the maximum bending moment, deflection, depth of plastic zone and settlement adjacent to sheet pile wall.

Ground Settlement and Deflection Response of Cantilever Sheet Pile Wall Subjected to Surcharge Loading

Sheet pile walls are used to support moderate height of excavation. If bracing system or anchors are not provided, it gets stability mainly from passive earth resistance below the dredge line. Non-availability of large open space in metro cities gives the perception to engineers to go deeper in the earth and use sheet pile walls for supporting various types of works like parking space and housing utilities. To avoid the damage to surrounding structure, proper analysis of settlement and deflection of the wall should be carried out. The deflection and settlement of wall depend on soil properties, depth of excavation and wall properties. In the present study, cantilever sheet pile walls are analyzed under surcharge loading for settlement and deflection through pseudo-static approach using finite difference-based program FLAC2D. A parametric study is carried out assuming an elastic–perfectly plastic Mohr–Coulomb model with non-associated flow rule by varying the seismic coefficients, embedded depth, soil–wall friction angle, type of soil, magnitude of surcharge and distance from the top of the wall. The results show that by increasing the coefficient of horizontal seismic acceleration, the deflection and settlement of cantilever sheet pile walls increase. It is also observed that with an increase in distance of surcharge from top of the wall, both settlement and deflection decrease.

Seismic active earth pressure on bilinear retaining walls using a modified pseudo-dynamic method

BackgroundProper understanding of seismic behavior of retaining structures is crucial during a strong earthquake event. In particular, response of retaining walls with bilinear backface, where a sudden change in the inclination along its depth make the problem more complex. This study focuses on estimating the seismic earth pressure coefficients of a retaining wall with bilinear backface using a modified pseudo-dynamic method.MethodsIn this method, the backfill soil is modeled as a visco-elastic Kelvin–Voigt material. A frequency-dependant amplification function is derived for the waves traveling along the backfill using well-established one-dimensional ground response analysis theory. A rigorous parametric study has been carried out to understand the effect of various parameters such as amplitude of base acceleration, direction of vertical acceleration, soil shear resistance angle, soil-wall friction angle, wall inclination, frequency ratio, and damping ratio on the seismic active earth pressure.ResultsIt has been observed that the damping ratio of the backfill soil plays an important role, particularly when the frequency of wave is close to the natural frequency of the backfill. Further, the seismic active thrust is found to increase in both upper and lower segments of the wall when the frequency of the primary wave is greater than that of the shear wave. Comparison of results with the previous studies indicates that the conventional pseudo-dynamic methods significantly underestimate the seismic coefficients and seismic pressures, particularly for the high-intensity motions.ConclusionsThe results of the study show that the natural frequency and damping of the backfill soil have significant effect on the seismic active earth pressure coefficients. Comparison with conventional pseudo-static and pseudo-dynamic methods indicates that the previous methods largely underestimate seismic coefficients and seismic pressures (as much as 48%). This under-estimation is more prominent for higher-intensity motions and less-damped soil, where the soil amplification effects pose most importance. This modified pseudo-dynamic approach can further be used for design of bilinear retaining structures.

Seismic Active Earth Pressure on Walls Using a New Pseudo-Dynamic Approach

Seismic active soil thrust, soil pressure distribution and overturning moment are obtained in closed form using a new pseudo-dynamic approach based on standing shear and primary waves propagating on a visco-elastic backfill overlying rigid bedrock subjected to both harmonic horizontal and vertical acceleration. Seismic waves respect the zero stress boundary condition at the soil surface, backfill is modeled as a Kelvin–Voigt medium and a planar failure surface is assumed in the analysis. Effects of a wide range of parameters such as amplitude of base accelerations, soil shear resistance angle, soil wall friction angle, damping ratio are discussed. Results of the parametric study indicate that amplitude of the horizontal base acceleration and soil shear resistance angle are the factors most influencing active pressure distribution whereas the presence of the vertical acceleration always results in a quite small increase in seismic active thrust. Damping ratio is important mainly close to the fundamental frequency of shear wave where seismic active thrust is maximum. Unlike the original pseudo-dynamic approach the effect of a different frequency for S-wave and P-wave is considered in the analysis. Seismic active thrust is found to increase when the frequency of P-wave is greater than that of S-wave. The results obtained by the proposed approach are found to be in agreement with previous studies, provided that the seismic input is adapted to include amplification effects.

Active earth pressure of retaining wall considering wall movement

The coulomb’s limit equilibrium theory is employed for the active earth pressure calculation of retaining wall considering translational wall movement. It is considered that the earth pressure against the back of the wall is due to the thrust exerted by a wedge of soil between the wall and a plane passing through the heel of the wall. The soil–wall friction angle and internal soil friction angle are obtained via the simulation of the unloading triaxial test. The basic equations are established by considering the force equilibrium of a partial soil wedge. The lateral earth pressure coefficient is achieved through the moment equilibrium of the whole soil wedge. Comparisons illustrating the accuracy of the proposed approach are made with solutions available in the literature.

Rankine pseudo-static earth pressure for c–ϕ soils

This study provides an analytical solution for calculation of seismic active earth pressure on the back of a rigid wall retaining cohesional–frictional (c–φ) soil. The proposed formulation is based on the conjugate stress concept, without employing any additional assumptions, similar to Rankine's original earth pressure formulation. The effects of sloping backfill and wall inclination are considered. In addition, a closed form solution has been derived for the soil–wall friction angle as a function of inertial forces and problem geometry for any given pseudo-static acceleration, as opposed to the constant value commonly employed in practice. The net seismic active force calculated based on the proposed formulations is found to be comparable with those obtained from previously published methods.

Passive earth pressure against retaining wall using log-spiral arc

Passive earth pressure against retaining wall depends on a number of factors such as, soil friction angle φ, soil wall friction angle δ, backfill angle (ground surface inclination behind wall β), inclination of wall face on horizontal α, and surface of rupture. Several theories have been developed to overcome this problem, i. e., determination of the coefficient of passive earth pressure using the plane surface of rupture. One of the important parameter which affect the coefficient of the passive earth pressure is the surface of rupture. In the present paper, formulation is proposed for calculating coefficient of passive earth pressure on a rigid retaining wall undergoing horizontal translation based on surface of rupture consisting of log-spiral and linear segments assisted by computer program (MATLAB program). The present study is compared with coulomb’s results. The comparisons of that the present study predicted values of earth pressure are much less than those of coulomb’s values specially if δ≥ 0.3 φ. These results agree well with another research. In order to facilitate the calculation of coefficient of passive earth pressure, using the proposed equations, a modified coefficient of passive earth pressure is provided. It is a function of (φ, δ, β, α).

Passive earth pressure against retaining wall using log-spiral arc

Abstract Passive earth pressure against retaining wall depends on a number of factors such as, soil friction angle ϕ, soil wall friction angle δ, backfill angle (ground surface inclination behind wall β, inclination of wall face on horizontal α, and surface of rupture. Several theory have been developed to over come this problem, i. e., determine the coefficient of passive earth pressure using the plane surface of rupture. One of the important parameter which effect on the coefficient of the passive earth pressure surface of rupture. In the present paper , formulation is proposed for calculating coefficient of passive earth pressure on a rigid retaining wall undergoing horizontal translation base on surface of rupture consisting log-spiral and linear segments assisted by computer program (MATLAB program used). The present study is compared with coulomb’s results. The comparison between present study and coulomb’s values shows the present study predict values of earth pressure much less than those of coulomb’s values specially if δ≥ 0.3 ϕ. Those results agree with anthers researches In order facilitate calculation coefficient of passive earth pressure, using the proposed equations, a modified coefficient of passive earth pressure is provided. It is function of (ϕ, δ, β, α).