Feasibility study for the southern extension of Mila town (northeast of Algeria) for urbanization purposes: a geotechnical and hydrogeophysical approach

The population of Mila is increasing and local authorities are looking for new lands to develop the town and provide housing. However, the soil of these lands is unstable and requires detailed studies to serve as a foundation. This work presents the geotechnical and the geophysical characteristics of the Marechau soils, which forms the southeast extension of the Mila town. To provide an idea about the soil condition, to choose the type of adequate constructions and to make decision for building it, we adopted a geotechnical approach, where we analysed the soils by carrying out core drilling tests, dynamic penetration tests and the laboratory tests. We also, employed the geophysical approach in determining the electrical resistivity so as to map the depth of bedrock roof. Furthermore, we conducted a comprehensive hydrogeological study, monitoring precipitation and the piezometric level of the aquifer over a period of 200 days, and determined the flow direction. The core drilling test results indicate a clayey soil with limestone blocks. The dynamic penetration test show two categories of soil. The laboratory tests show that the materials analysed are very plastic, over-consolidated and medium to very compressible. They have a medium to high swelling potential and medium amount of aggressiveness to concrete. Besides, the tomography results also showed a single layer land (clay) with massive rocks embedded in it. The piezometric monitoring reveals the presence of two aquifer systems. The first is superficial and the second is deep. They don’t recharge directly after the rain falls and the groundwater flows in the direction of the slope. All the results indicate that solutions must be found for soil movements in the area under study before urbanization takes place. The combination of these results with the location, land morphology, tectonic activity, and seismotectonic aspects suggest that the area presents a high risk, and its urbanization requires rigorous and mandatory precautionary measures.