1923
Design, Construction and Monitoring of a Mixed Soil-Reinforced and Anchored
Retaining Wall in Expansive Soil
Conception, construction et surveillance d'un mur mixte de sol renforcé et ancré dans un sol
gonflant
Abramento M.
CEG Engenharia and Escola Politécnica da US
P
Fujii J.; Cogliati B., Assakura V.
Yamamichi and CEG Engenharia
ABSTRACT: Due to traffic volume increase a large strecth of a major highway linking São Paulo and Campinas City, Brazil, has
recently been widened. In order to achieve the construction of additional lanes, a construction of a mixed-type retaining wall became
necessary. This mixed-retaining structured consisted of a 5m high anchored wall at the bottom and a 5m high steel-reinforced
retaining wall at the top, totalling a 10m high retaining wall. The bottom wall was built in a cut slope in a stiff, highly expansive,
clayey soil. The steel-reinforced retaining wall was built over the lower anchored wall with both faces aligned. Anchor loads at the
bottom wall were applied in stages in order to account for the increasing loads during the construction of the top wall. In order to
correctly design the bottom anchored wall several undisturbed soil samples were obtained from the stiff clay. Laboratory tests
included complete caracterization, shear strength and expansion pressure determination. The retaining system was monitored during
all construction stages. This paper presents details on the laboratory tests results, design of the retaining walls, construction steps and
monitoring.
RÉSUMÉ : En raison du volume de trafic une portion d'une route importante reliant São Paulo et Campinas, au Brésil, a récemment
été élargie. Afin de réaliser la construction de voies supplémentaires, une construction d'un mur de type mixte devenait nécessaire.
Cette structure mixte consistait en un mur ancré de 5m de haut en partie basse et un mur en sol renforcé en partie haute, pour une
hauteur totale de 10m de soutènement. La paroi en partie basse a été construite dans une pente en déblai dans un sol argileux raide et
très expansif. Le mur en sol renforcé t a été construit sur la paroi inférieure ancrée avec les deux parements alignés. Les charges
d'ancrage de la paroi en partie basse ont été appliquées par paliers afin de tenir compte des charges croissantes au cours de la
construction de la paroi supérieure. Afin de concevoir correctement le mur ancré plusieurs échantillons de sol intacts ont été prélevés
sur l'argile raide. Les tests de laboratoire incluent la caractérisation complète, la résistance au cisaillement et à la détermination des
pressions de gonflement. Le système de soutènement a été suivi pendant toutes les étapes de la construction. Cet article présente des
détails des résultats des tests de laboratoire, la conception des murs de soutènement, la construction et le suivi des mesures.
KEYWORDS: Reinforced wall, anchored wall, expansive soil, monitoring
1 INTRODUCTION
Due to traffic volume increase a section of approximately 3km
of a major highway linking São Paulo and Campinas city,
Brazil, had to be widened. In order to achieve the construction
of additional lanes, and due to geometric constraints, a mixed-
type retaining wall became necessary. This mixed-retaining
structured is shown in Figure 1 and consists in a 5m high
anchored wall at the bottom and a 5m high steel-reinforced
retaining wall at the top, totalling a 10m high retaining wall.
This paper presents details on the laboratory tests results,
design of the retaining walls, construction steps and monitoring,
as well as a comparison of measured and predicted
displacements and loads at the top and bottom retaining walls.
2 SITE INVESTIGATION AND LABORATORY TESTS
SPT borings show that the local soil consists of a superficial
colluvial soil characterized as a soft porous silty clay 2 to 3m
thick and with blowcounts varying from 2 to 3, followed by a
medium, stiff and hard clay with blowcounts larger than 15 and
reaching up to 40. A picture of this last layer is shown in Figure
Figure 1. Typical cross-section of mixed reinforced fill-
anchored wall.
2. Figures 3 and 4 show typical SPT borings results for two of
the wall sections. This stiff clay layer receives the load from the
