Spatial mapping of the limit pressure in the lowland soils of the Yaounde region (Cameroon)

The aim of this study is to produce a spatial map of limit pressure values in the soils of a lowland site in Yaoundé (Cameroon). It is based on conventional static and spatial analyses of limit pressure values obtained through a series of Menard pressuremeter tests. Descriptive statistical analyses are used to characterise the level of dispersion between the data. The Pearson correlation matrix constructed using Python 3.7 software highlights the level of correlation between the pressuremeter test points. Empirical Bayesian Kriging interpolation in ArcGIS 10.8 enables the modelling of variograms, the creation of maps, and the evaluation of their performance and geotechnical implications. The descriptive statistical analysis highlights a standard deviation ranging from 0 to 2 for coefficients of variation ˃35%, skewness values ranging from 0 to 2, and kurtosis values ranging from 1 to 7. This confirms the prevalence of extreme values and the high dispersion of the data, which has an asymmetric distribution. Weak correlations (˂ 0.4) predominate among the eighteen survey points. The variograms show nuggets of virtually zero and the absence of a pure nugget effect in all layers. The Pl values shown on the map scale are close to the actual field survey results. The RMSSE is predominantly within the range [0.9 – 1.1]. The interpolation maps produced using the exponential model with log-empirical transformation thus show good accuracy in the majority of layers. It is possible to make foundation recommendations based on the Pl value classes, which are distinguished by different colours on the map. These include light yellow areas (Pl ≤ 0.6 MPa) where the soil lacks the necessary strength to support a structure, dark yellow areas (0.6 ˂ Pl ≤ 1.4 MPa) suitable for strip footings or raft foundations for light structures, and brown areas (Pl ˃ 1.4 MPa) capable of supporting isolated footings or piles for heavy structures.