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Rigid retaining walls with polyline backs are possibly used in filling engineering, and some types of these walls may have better stability than ordinary gravity walls with planar backs. Aiming at the active earth pressure on polyline-back walls under the translation mode, an analytical method within the frame of limit equilibrium is provided according to the potential two slip surfaces intersected in the retained backfill. The proposed method focuses on the minimum slide-resisting factor of safety of the polyline-back wall to be the objective function, and it can be performed easily using the nonlinear programming approach. Analysis results of some examples show that the proposed earth pressure is close to those obtained using the test and numerical methods with an average error of about 15%. The platform width and the ratio of the upper to lower wall height in the counterweight wall have more obvious influences on earth pressure than the slip surfaces. The overall and local critical slip surfaces are considerably influenced by the lower-back and backfill surface inclinations, respectively. The counterweight wall is the optimum configuration for the overall sliding stability among the compared five polyline-back walls due to its outward-extending platform and positively inclined lower back. Practical Applications: This work provides a calculation method for the active earth pressure on rigid walls with polyline backs under wall translation, which holds practical significance for geotechnical engineers or practitioners in filling engineering such as embankments. The proposed method can analytically solve the active earth pressure on different segments of the polyline back of gravity walls and the two critical slip surfaces intersected in the retained soil. As a result, the slide-resisting stability of the wall can be analyzed in the design. The proposed method can be used further to compare possible different types of polyline backs of a wall and then for the quick optimization design of the gravity wall. Analysis results of an example show that the counterweight wall is the optimum configuration for overall sliding stability due to its outward-extending platform and positively inclined lower back. In brief, this work can provide a significant reference for the practical design of rigid walls with polyline backs, such as counterweight walls and hunchbacked walls, based on the easily operated limit equilibrium methods. [ABSTRACT FROM AUTHOR]

This paper introduces a new retaining structure, multi-step cantilever retaining walls pulled locally with geogrids, which has advantages of light weight, quick installation and good applicability for high fill earthworks. Considering log-spiral rotation failure mechanism passing by the heel of the lowest wall members as well as pull-out failure and tensile rupture of the flexible reinforcements, an analytical procedure for seismic overall stability of the retained embankment is proposed based on the upper-bound limit analysis method combined with pseudo static approach. Analysis results of a practical example show that the proposed safety factor and critical slip surface are identical with those by numerical simulation method via FLAC3D. The safety factor increases approximately linearly with the ultimate tension force and the number of reinforcements and nonlinearly with the length of reinforcements within a certain range. Horizontal seismic force has noticeable effect on the slope stability, and vertical seismic effect becomes significant under high horizontal acceleration coefficient. The safety factor is decreasing and the critical slip surface develops obviously towards the embankment exterior as the total number of vertical wall members increases. Besides, the distribution width and setback distance from the walls of the strip surcharge have certain effects on the retained slope stability. [ABSTRACT FROM AUTHOR]

The factor of safety of a slope ([F.sub.s]) is invariably assessed using methods underpinned by moment, force, and (or) Shear strength equilibrium concerning slip surfaces. Each method inherently embeds some form of limitations, despite being popularly adopted in practice. In this paper, a new [F.sub.s] is devised using the ratio of ultimate energy ([e.sub.u], upon sliding) over accumulated 'elastic' energy. The [F.sub.s] is then reduced to a simple expression of the power to shear stress and shear strength, by taking soil as an elastic-plastic material obeying the Mohr-Coulomb failure criterion. This expression empowers significant efficacy in gaining the factor of safety (without involving energy or directions of shear stresses). The [F.sub.s] values were calculated for three typical slopes concerning various mechanical properties (dilation, Poisson's ratio, and shear modulus) and effective computational strategies. All of the [F.sub.s] values (to a congruous accuracy of available methods) were obtained in less than 1% the time of conventional numerical analyses. The proposed [F.sub.s], equally applicable to limit equilibrium methods, may be utilized in practice to expedite slope design. Key words: slope, stability analysis, deformation energy, factor of safety, slip surface. Le facteur de securite d'une pente ([F.sub.s]) est evalue a l'aide de methodes invariablement soutenues par moment, force, et (ou) d'equilibre de la resistance au cisaillement sur des surfaces de glissement. Chaque methode integre intrinsequement une certaine forme de limites, en depit d'etre communement adoptee dans la pratique. Dans cet article, une nouvelle [F.sub.s] est mise au point en utilisant le rapport d'energie finale ([e.sub.u], sur glissement) sur une energie accumulee elastique. Le [F.sub.s] est alors reduit a une simple expression de la puissance a une contrainte de cisaillement et la resistance au cisaillement, en prenant le sol comme un materiau elastoplastique obeissant aux criteres de rupture de Mohr-Coulomb. Cette expression donne efficacite significative pour obtenir le coefficient de securite (sans impliquer l'energie ou de directions de tensions de cisaillement). Les valeurs [F.sub.s] ont ete calculees pour trois pistes typiques concernant diverses proprietes mecaniques (dilatation, coefficient de Poisson, et le module de cisaillement) et des strategies de calcul efficaces. Toutes les val[e.sub.u]rs [F.sub.s] (pour une precision discontinue de methodes disponibles) ont ete obtenues en moins de 1 % du temps d'analyses numeriques classiques. Le [F.sub.s] suggere, egalement applicable aux methodes d'equilibre de limite, peut etre accorde dans la pratique pour accelerer notre conception de la pente. [Traduit par la Redaction] Mots-cles : pente, analyse de stabilite, energie de deformation, coefficient de securite, surface de glissement., Introduction Slope stability is largely evaluated in light of the limit equilibrium method (LEM) (Fellenius 1936; Bishop 1955; Janbu 1973; Morgenstern and Price 1965; Spencer 1967; Chen and Morgenstern 1983; [...]

When the pseudo-static method is used to calculate the seismic active earth pressure on rigid retaining walls, the applied seismic inertia forces can be assumed as two modes, namely, the dispersed action in the slide mass and the concentrated action at the centroid of the slide wedge. In order to determine the difference of calculation results between the two modes for the seismic active earth pressure under general conditions including wall back inclination, layered backfill and surface strip load, an oblique slice method with each slice parallel to the soil surface is adopted to obtain recursive calculation formulas of the earth pressure in the dispersed and concentrated action modes based on limit equilibrium conditions. The proposed method can attain the magnitude and distribution mode of the seismic active earth pressure. Case analysis shows that the proposed results are consistent with those using shake table test and numerical simulation method. The values of the resultant force of seismic active earth pressure in the two modes are equal, but there are obvious differences in the distribution mode and the position of application point of the resultant. The application point via the concentrated mode is higher than that via the dispersed one. The difference between them first increases and then decreases with the increase of horizontal seismic coefficient from zero. If the horizontal seismic coefficient is assumed as 0.2, the ratio of the height of application point of the active earth pressure over the wall height is about 0.7 and 0.48~0.56 respectively in concentrated and dispersed modes, and the corresponding difference between the two modes reaches the maximum. As for the wall stability and bearing capacity of the foundation, calculation results in the concentrated mode are both safer than those in the dispersed mode. [ABSTRACT FROM AUTHOR]