An integrative approach for preliminary environmental engineering investigations amidst reclaiming desert-land: a case study at East Nile Delta, Egypt

Scientific interest within the desert-lands lies on mapping the near-surface clayey soils being made environmental engineering problems, e.g., water logging and cracked pavements. As a starting point used for urban rational development, boreholes, direct current resistivity (DCR) soundings and electrical resistivity tomography surveys and preliminary geotechnical studies are employed in an integrative approach for mapping and characterizing the foundation soil. This study is carried out at one of the main urban reclamation projects amidst desert fringes of East Nile Delta, Egypt, as a case study, where the in situ soil properties are variable even within a short distance and, consequently, difficult to be predicted. Conventional and non-conventional inversion approaches are applied for solving the inverse problems of DCR data. The results are calibrated with the drilled borehole lithology. Two main geoelectrical resistivity layers are distinguished: the upper medium to high-resistivity soils corresponding to surface poorly graded sand with gravels underlain by low-resistivity layer attributing to clayey sand with calcareous materials. The inversion results show the sequential joint use efficiency of the two approaches in mapping the near-surface layer boundaries providing realistic soil heterogeneities tomography. In respect of such results and from an engineering point of view, the exaggerated clayey soils are highly saturated in some places representing (1) medium plasticity, moderate-to-high swelling and (2) low compressive strength. It is conceivable that such soils can exhibit geotechnical problems, especially under wetting conditions. Consequently, the integrative approach is cost-effective and opens the way for engineers on where prioritized interventions are required to the urban expansion.