Base de aterros sobre solos moles com inclusões rígidas, estudo do caso: baixa do Rio Maputo em Salamanga

Abstract

When the foundation soil consists of large thicknesses of soft soils, hard inclusions have been used to transfer embankment loads to the more resistant layers. Although soft soils are poorly suited to embankment construction, it is not always possible to avoid them. In fact, soft soils have low bearing capacity, making them unsuitable for resisting embankment loads. In fact, the use of rigid inclusions associated with geogrids is an alternative, whereby the embankment load is transferred through the rigid inclusions to the resistant soil layer. Although comparatively expensive, the benefits of this alternative are rapid construction and reduced maintenance over the lifetime of the project. This study aims to analyse the behaviour of the embankment base on soft soils, using analytical methods (Hewlett and Randolph -1988; Low et al -1994 and Abusharar et al - 2009) and the finite element method (PLAXIS 2D v8.6 software). Stability analysis is also performed using the software Slide 2 v.6. The case study of the lower Maputo River in Salamanga demonstrated the effectiveness of this alternative in solving the problem of excessive settlement, as well as the problem of stability. It was also demonstrated that the efficiency of the system (embankment-foundation) increased with the introduction of geogrid reinforcement (membrane effect), as well as with an increase in the height of the embankment. On the other hand, the increase of the spacing between the rigid inclusions evidenced the reduction of the efficiency. At last, it is noted that the introduction of the geosynthetic does not contribute to the reduction of settlements, however it improves the stability of the embankment. The camber effect improves with increasing embankment height