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The search for and knowledge of the best conditions for anchoring the foundations of certain structures such as bridges, tunnels and quays in sedimentary estuaries is a challenge, for both scientists in general and engineers in particular. Indeed, wharves are structures that receive a lot of stresses and therefore require anchoring to avoid tilting and to guarantee their stability during service. This work, based on the analysis of data from seismic refraction methods, mechanical soundings and laboratory tests, characterises the terrain of the Wouri estuary in Central Africa. The objective is to determine and present the subsurface layers encountered as well as their characteristics, in order to define the best conditions for anchoring the foundations to ensure the stability of the quays to be built there. The seismic refraction campaign shows that the study area is relatively heterogeneous over the first 25 m, with velocities measured in the range 1520–1750 m/s; modulated in two distinct ranges, between 1520–1580 m/s characteristic of mud and loose sediments (alternating layers of clay, sand, loose silt) and the range 1580–1750 m/s corresponding to the signature of sandy-silty or compact clays. The mechanical tests show sedimentary soils, with alternating layers of sandy clay and clayey sand over the 42 m drilled, loose over the first 30 m in the bank area and over the first 15 m in the canal or dredge area, with a limit pressure of less than 1 MPa. Similarly, the soil samples taken and tested in the laboratory show that the soils are clayey over the first 30 metres, plastic and liquid with respect to their water content, respectively, below and above the liquidity limits, confirming their loose character. The results of seismic refraction, mechanical soundings and laboratory tests show that, in estuarine areas characterised by alternating sandy clay and clayey sand, there are not always hard formations in the first 25 metres of depth but, from a depth of 30 m, the soils become moderately compact and begin to form an anchoring layer sufficient to guarantee the stability of the quays against earth pressure forces. [ABSTRACT FROM AUTHOR]

• In this work we study the stability of 10 embankments on some main roads in central Africa. • We find that, in general, these embankments are not stable. • To improve this situation, we propose to plaster, slice or cut some of these slopes with angles lower than 10°. Analysis of slope stability has been a challenge for researchers and engineers since the 17th century with Hooke. This paper used geometric, kinematic and seismic methods to analyse the stability of selected slopes cut into the gneiss of important roads connecting Central Africa countries, subjected to particle and block falls. The selected slopes were also studied to verify the factor on which engineers base their design. The results show that the angles are sharp and that the selected slopes are unstable, made in gneiss with a diptic state and a particle acceleration of 1.57 km/s2, confirming that the slopes are sensitive to falling particles. This study also shows that, in a moderately active seismic zone in Central Africa, slopes cut into fractured gneiss are generally unstable and engineers must also consider FS. To make these slopes more stable, they can be plastered, trenched or cut at angles <10°. [ABSTRACT FROM AUTHOR]