Stability of Shallow Foundations in Dynamic Sites through Geotechnical Optimization Using the Piezocone (CPTu): The Case of Cotonou Airport’s Site in the Republic of Benin

Kassa Issifou Mounou Sambieni^{1, 2,}

¹Materials and Structures Laboratory (LAMS), Cotonou, Benin

²National Public Works Testing and Research Company (SNERTP), Cotonou, Benin

Cite this paper:
Kassa Issifou Mounou Sambieni. Stability of Shallow Foundations in Dynamic Sites through Geotechnical Optimization Using the Piezocone (CPTu): The Case of Cotonou Airport’s Site in the Republic of Benin. American Journal of Civil Engineering and Architecture. 2026; 14(5):202-209. doi: 10.12691/ajcea-14-5-3

Abstract

The stability of airport infrastructure is critical to preventing structural cracks, preserving high-precision equipment, and maintaining air traffic under heavy, repetitive loads. In this context, an in-situ geotechnical characterization and shallow foundation design study was conducted for a building at Cotonou Airport. The geotechnical investigations were based on three piezocone tests (CPTu) carried out to refusal depths of 8.0 to 9.0 meters. The measurements indicate a water table located 3.50 meters below the natural ground level. The site's stratigraphy consists of a 1.3- to 1.5-meter-thick surface horizon of sandy-silty fill, overlying a substratum of moderately clean, fine sands. The results of the core strength profiles reveal average surface compaction down to a depth of 2.5 or 3.0 meters, followed by very high compaction (highly densified) in the sandy bedrock beyond 3.0 meters. The foundation design and verification were carried out in accordance with standard NF P94-261 (application of Eurocode 7). For an anchorage at -2.5 m, the design stress is limited to 300 kPa at the serviceability limit state (SLS) (approximately 492 kPa at the ultimate limit state). The minimum required embedment depth is set at 0.8 m for Area 1 and at 2.5 m for Areas 2 and 3. Absolute settlements of less than 10 mm will be instantaneous during construction due to the sandy soil. Finally, a rigorous quality assurance protocol will validate the conformity of the backfill, concrete, and inclusions. The methodological application and technical optimization, combining high-precision piezocone tests (CPTu) and numerical modeling via FOXTA software, made it possible to define custom anchors and demonstrate instantaneous settlements of less than 10 mm, guaranteeing the stability of the infrastructure.

Keywords:
Stability shallow foundations piezocone CPTu settlements sandy soil FOXTA

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