Effect of the Soil under Retaining Wall Footings on the Resulted Earth Pressure

Hany F. Shehata

In the proceedings of: GeoRegina 2014: 67th Canadian Geotechnical Conference

Session: Earth Walls and Foundations

ABSTRACT: This paper presents the effect of the rigidity of soil under a retaining wall's base on the lateral earth pressure and the maximum bending moment. Usually, the earth pressure that is acting from the backfill on the cantilever retaining wall is active. The most common method used for the calculation of the earth pressure on the retaining wall is Rankine's Theory, which is mainly based on the wall movement. The wall needs to move for the soil to be considered active. This method cannot take into account the effect of the rigidity of the soil under footing on the earth pressure. In addition, it cannot take into account the width of the footing embedment inside the backfill. The earth pressure depends on the value of the wall displacement, the soil under the footing base, the wall rigidity, and the embedment width inside the backfill. In this paper, many retaining wall models with different rigidities that, resting on soils with different properties, were analyzed. There were significant effects of the rigidity of the soil under footing and footing embedment depth on the maximum bending moment and the lateral earth pressure distribution. Thus, Rankine's theory is satisfactory in most cases. RÉSUMÉ Cet article présente l'effet de la rigidité du sol sous la base d'un mur de soutènement de la pression latérale des terres et le moment de flexion maximal. Habituellement, la pression de la terre qui agit à partir du remblai sur le mur de soutènement cantilever est actif. La méthode la plus couramment utilisée pour le calcul de la pression de la terre sur le mur de soutènement est la théorie de Rankine, qui est principalement basé sur le mouvement de la paroi. Le mur doit se déplacer pour le sol pour être considéré comme actif. Cette méthode ne peut pas prendre en compte l'effet de la rigidité du sol sous un pied sur la pression de la terre. En outre, il ne peut pas tenir compte de la largeur de l'encastrement de pied à l'intérieur du remblai. La pression de la terre dépend de la valeur du déplacement de paroi, le sol sous la base de la semelle, la rigidité de la paroi, et la largeur de l'enfoncement à l'intérieur du remblai. Dans cet article, de nombreux modèles de mur de soutènement avec différentes rigidités qui, reposant sur des sols ayant des propriétés différentes, ont été analysés. Il y avait des effets significatifs de la rigidité du sol sous un pied et un pied de profondeur d'ancrage sur le moment de flexion maximale et la répartition de la pression latérale des terres. Ainsi, la théorie de Rankine est satisfaisant dans la plupart des cas. 1 INTRODUCTION In Terzaghi's (1934) classic experiments with a large-scale model retaining wall, it was found that only a small amount of movement, 0.25% of the wall height, was required to achieve the active condition and that a larger amount of movement, 1% of the wall height, was required to achieve the passive condition. Morgenstern and Eisenstein (1970) compared Rankine's theory, which assumes no wall friction, to several approaches that do account for wall friction and found that for the active condition, the other theories were all within approximately 10% of each other. To determine the earth pressure, Coyle et al. (1974) installed EPCs behind a 4.9 m -16 ft- high cantilever retaining wall resting on H piles. The soil translation was measured relative to a fixed point using an engineer's steel tape. The displacement of the stem from vertical was recorded using a plumb bob suspended from the top of the wall as a vertical reference line. The earth pressure compared well with the theoretical active pressure for the top 2.1 m -7 ft- of the wall but was between the active and at-rest values for the bottom of the wall. Coyle and Bartoskewitz (1976) presented results from instrumenting a 3 m -10 ft- high, 3.7 m -12 ft- wide precast panel retaining wall founded on drilled piers. The lateral earth pressure data were very similar to the data from Coyle et al. (1974) in that the earth pressure reduced to active levels at the top of the wall, but not at the bottom. Most wall movement during backfilling was in the form of translation, but some rotation and translation away from the backfill occurred for a few months after the backfilling ended. Several studies have used finite element analyses of concrete retaining walls, including gravity walls _Clough and Duncan (1971); Kulhawy (1974) and cantilever walls Horvath (1991); Goh (1993). Clough and Duncan (1971) examined the behavior of a wall founded on sand using increasing loads to simulate the placement of backfill Goodman and Brown (1963); Clough and Woodward (1967). Goh (1993) modeled the backfilling in a similar manner and found that a cantilever wall rotated into the

RÉSUMÉ: t of the Soil under Retaining Wall Footings

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Cite this article:
Hany F. Shehata (2014) Effect of the Soil under Retaining Wall Footings on the Resulted Earth Pressure in GEO2014. Ottawa, Ontario: Canadian Geotechnical Society.

@article{GeoRegina14Paper136,author = Hany F. Shehata,title = Effect of the Soil under Retaining Wall Footings on the Resulted Earth Pressure,year = 2014}