Etude des caractéristiques résiduelles des sols du site instable de Bouchegouf (Algerie)

Résumé

Cet article présente une étude comparative des caractéristiques résiduelles obtenues à l'aide de l'appareil de cisaillement annulaire et de la boite de cisaillement alterné. Les échantillons de sols étudiés proviennent du site instable de Bouchegouf (Algérie). Des corrélations entre les différents paramètres pouvant influer sur ces caractéristiques résiduelles ont été faites. Il a été, notamment, montré que les résultats obtenus à l'aide de l'appareil de Bromhead sur des échantillons remaniés sont très voisins de ceux obtenus à l'aide du cisaillement alterné sur des échantillons intacts quand la fraction argileuse est importante.

Abstract

 The site of Bouchegouf has been the subject of several slope instabilities in the past. In 1990, the reactivation of a major slip has led to the closure of the main road link between two large cities located in the eastern part of Algeria. This paper presents a comparative study on the residual shear strength characteristics of the soils from this particular site. The soils were sampled from two different locations close to the slip plane. A continuous rotational shear device and a modified direct shear device have been used to obtain the residual shear strength parameters. All shear tests have been carried out on remoulded samples (for the rotational shear) and undisturbed samples (for the direct shear) under normal stresses varying between 50 kPa and 200 kPa. The salient observations which can be drawn from the present work are:

1. Mineralogy is an important factor for the characteristics of the residual parameters. It was found that soils which had an important illite/kaolinite content had a higher residual resistance than soils with a high montmorillonite content.

2. If the clay content is very important (>70%) the results obtained from the alternating shear device are close to the those obtained from the rotational shear device.

3. An inverse relationship exists between the Atterberg limits and the calcite content. However, the calcite content found on the Bouchegouf site did not influence the residual parameters.