Passive Earth Resistance Research Articles

Evaluation of Passive Earth Resistance Using an Improved Limit Equilibrium Method of Slices

Abstract The present study proposes a new approach to solve passive earth pressure problems using the method of slices, coupled with the limit equilibrium (LE) technique. Unlike existing LE studies...

Passive resistance of unsaturated backfill under steady state flow conditions

ABSTRACT This paper presents a unified semi-analytical solution to investigate the passive earth resistance of unsaturated soils retained by a rigid wall in the framework of limit-equilibrium approach based on a rotational log-spiral failure mechanism. Coupled influences of unit weight and suction stress changes in unsaturated soils under different steady vertical flow conditions have been considered to provide a more realistic solution. The impact of different parameters such as effective internal friction angle soil, inclination of backfill surface and wall back face, surcharge pressure, height of wall, location of water table, and soil–wall interface friction has been explored by performing a parametric study. It has been found that the changes in the suction stress and unit weight of unsaturated soils under different input parameters have a greater effect on modifying the critical slip surface, and magnitude and point of application of passive earth resistance on the retaining walls. The results obtained from the present study compare reasonably well with the solutions in the literature.

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 passive earth resistance using modified pseudo-dynamic method

In earthquake prone areas, understanding of the seismic passive earth resistance is very important for the design of different geotechnical earth retaining structures. In this study, the limit equilibrium method is used for estimation of critical seismic passive earth resistance for an inclined wall supporting horizontal cohesionless backfill. A composite failure surface is considered in the present analysis. Seismic forces are computed assuming the backfill soil as a viscoelastic material overlying a rigid stratum and the rigid stratum is subjected to a harmonic shaking. The present method satisfies the boundary conditions. The amplification of acceleration depends on the properties of the backfill soil and on the characteristics of the input motion. The acceleration distribution along the depth of the backfill is found to be nonlinear in nature. The present study shows that the horizontal and vertical acceleration distribution in the backfill soil is not always in-phase for the critical value of the seismic passive earth pressure coefficient. The effect of different parameters on the seismic passive earth pressure is studied in detail. A comparison of the present method with other theories is also presented, which shows the merits of the present study.

Seismic passive earth resistance in submerged soils using modified pseudo-dynamic method with curved rupture surface

ABSTRACTThe sparsity of examination of seismic passive earth pressure acting on retaining wall holding soil backfill with full submergence, which is more common in waterfront areas, can be noticed from the literature. In the current study, a closed-form solution to compute the seismic passive earth pressure on nonvertical rigid retaining wall retaining a backfill with full submergence is proposed using the modified pseudo-dynamic approach. A nonlinear rupture surface (logarithmic spiral + straight line) in a submerged backfill of viscoelastic nature has been assumed. The presented modified pseudo-dynamic method overcomes the limitations of the existing pseudo-dynamic method for submerged soils. The proposed methodology has been thoroughly validated with the available literature. The influences of seismic acceleration coefficients, excess pore water pressure ratio, wall inclination, and soil and wall friction angles have been studied. It has been noticed that the consideration of excess pore pressure ratio leads to significant decrease in seismic passive resistance of the soil which in turn lead to extra hydraulic pressure acting on the wall in submerged backfill. There is a 57% decrease in seismic passive earth pressure coefficient as the wall inclination changes from −15° to 15°.

Influence of non-breaking wave force on seismic stability of seawall for passive condition

Proper design of seawall in earthquake prone region is one of the major concerns in geotechnical earthquake engineering. This paper presents the stability analysis of seawall under the combined action of earthquake forces, non-breaking wave force, hydrostatic and hydrodynamic forces and uplift force. Stability of seawall is assessed in terms of its factor of safety against landward sliding and landward overturning modes of failures. Seismic passive earth resistance has been calculated using pseudo-static approach. A detailed parametric study has been conducted to study the effect of non-breaking wave height, depth of water on seaward and land ward sides, soil and wall friction angles, and horizontal and vertical seismic accelerations. The factor of safety against overturning mode of failure decreases by about 52%, for a change in the ratio of non-breaking wave height to the depth of water on seaward side from 0 to 0.60. Present study shows that the seismic stability of seawall is more sensitive to non-breaking wave height, soil friction angle, wall friction angle and horizontal seismic acceleration. Proposed closed-form solutions and design charts can be used for the seismic design of seawall for passive case under the combined action of earthquake and non-breaking wave forces.

Reply to discussion of “Pseudodynamic approach for computation of seismic passive earth resistance including seepage” by Syed Mohd Ahmad [Ocean Engineering 63 (2013) 63–71

Reply to discussion of “Pseudodynamic approach for computation of seismic passive earth resistance including seepage” by Syed Mohd Ahmad [Ocean Engineering 63 (2013) 63–71

Discussion on “Pseudodynamic approach for computation of seismic passive earth resistance including seepage” by Syed Mohd Ahmad [Ocean Engineering 63 (2013) 63–71

Discussion on “Pseudodynamic approach for computation of seismic passive earth resistance including seepage” by Syed Mohd Ahmad [Ocean Engineering 63 (2013) 63–71

Pseudodynamic approach for computation of seismic passive earth resistance including seepage

The present paper highlights the importance of seepage force on the seismic passive earth resistance when the backfill is saturated. Simple limit equilibrium analysis has been carried out. The seismic passive earth resistance has been calculated by using the pseudodynamic approach. For seepage two individual cases of the movement of water within the backfill have initially been considered and then based on the analysis a critical combination has been ascertained. Simple and easy to follow equations for modified seismic passive earth pressure coefficients have been developed. To study the effect of various parameters, a detailed parametric study has been carried out and critical recommendations have been made with regards to each one of these. To demonstrate the applicability of the developed methodology, results in the form of graphs and tables have been presented. These graphs, combined with the developed simple equations, can provide a cue to the design engineers about how the seepage force affects the seismic passive earth resistance.

Finite Element Limit Analysis of Passive Earth Resistance in Cohesionless Soils

This note examines the classic passive earth resistance of cohesionless soil by using two newly developed numerical procedures based on finite element formulations of the bound theorems of limit analysis and non-linear programming techniques. Solutions using upper and lower bounds are presented to complement the previous studies of this problem. The parameters studied are soil-wall interface friction, wall inclination, backfill surface configuration and the wall's weight.

Lower-bound approach for seismic passive earth resistance

Current practice for computing earth pressure on earthretaining structures in the presence of seismic action relies on an extension of the Coulomb solution, due to Okabe and Mononobe & Matsuo, and referred to in the literature as the Mononobe-Okabe approach. This paper is intended to contribute to this problem by deriving an analytical solution for passive earth resistance coefficients in the presence of seismic actions, based on the lower-bound theorem of plasticity. The novelty of the present contribution lies in a transformation of axes that allows the problem of seismic passive resistance to be solved using the same stress field equations as the usual static case

Seismic passive earth pressure coefficients using the method of characteristics

The method of characteristics was used to generate passive earth pressure coefficients for an inclined wall retaining cohesionless backfill material in the presence of pseudostatic horizontal earthquake body forces. The variation of the passive earth pressure coefficients Kpqand Kpγwith changes in horizontal earthquake acceleration coefficient due to the components of soil unit weight and surcharge pressure, respectively, has been obtained; a closed-form solution for Kpqis also provided. The passive earth resistance has been found to decrease sharply with an increase in the magnitude of horizontal earthquake acceleration. The computed passive earth pressure coefficients were found to be the lowest when compared to all of the previous solutions available in the literature.Key words: earth pressures, earthquakes, method of characteristics, retaining walls, sands.

Seismic passive earth pressure coefficients for sands

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.

Anchored Bulkheads with Sloping Dredge Lines

Tests were conducted to determine the effect of a sloping dredge line on passive earth resistance in front of a bulkhead and bending moments in sheet piling. Results are interpreted relative to moment reduction procedures in current use.

Lateral forces on steered tyres in loose soil

In the introduction several samples were given to show under what circumstances lateral forces can occur on steered pneumatic tyres in agricultural soil. With the aid of a test setup developed for this purpose the lateral forces and rolling resistances, together with wheel sinkage and the negative wheelslip occurring on the steered front wheels of tractors and on tyres of agricultural machinery, were measured in the soil tank of the Institute for Agricultural Machinery of the Technische Hochschule Munich. The rolling resistance coefficients, which are already very high at zero slip angle on loosely cultivated soil ( ϱ=0·2), are doubled, however, at a slip angle of 20°. For a 28° slip angle, maximum rolling resistances of 70 per cent of the wheel load result! The lateral force coefficients increase less steeply than on a rigid track, but they attain higher values at larger slip angles. With increasing diameter the rolling resistance coefficients, as is to be expected, become smaller, and the lateral force coefficients larger. With incresing tyre width both the lateral force coefficients and the rolling resistance coefficients decrease. For this kind of loose soil the inflation pressure of the tyre brings about only a small reduction in the rolling resistance coefficients. The rut depth and the amount of negative wheelslip increase with the slip angles. Hence for a large slip angles a wide and deep rut results. Furthermore, attempts were made to establish a theory of lateral forces on a yielding soil. With the aid of an analytically representable simple pressure distribution within the contact area, and by analogy with lateral force theories for a rigid track, an equation for the lateral shear stress distribution in the bearing area could be found. To this, the lateral pressure exerted on the wheel segment that has penetrated into the soil during an inclined travel direction has to be added as another lateral force component. Again a relationship could be determined for this, analogous to the passive earth resistance. The agreement between measurement and calculation, despite the assumptions and simplifications, is satisfactory.