3-D soil-resistance maps in the presence of a strong vertical trend

Knowledge of the distribution of soil types and the behavior of the corresponding geotechnical properties is relevant for various civil engineering applications. This information is needed, among others, for city planning, environmental management, determination of slope stability, and foundation design. Considering the importance of geotechnical parameters for any civil engineering project, mapping this information is crucial. The Standard Penetration Test (SPT) is widely used as a geotechnical field test to characterize the soil profile. As the SPT provides information related to a specific point, it is necessary to extend this information to a large area, by filling the voids between sampling points. Civil engineers often carry out this interpolation using inappropriate practices, and the result is hence not always satisfactory. Therefore, methods that combine SPT and geostatistics are proposed for the generation of estimation maps that provide adequate tools for the decision-maker. The dataset used herein is composed of 141 SPTs carried out in an urban area spread over 5 km2. The data obtained show a strong vertical trend, as expected. Soil resistance is estimated from 50 × 25 × 1-m grid blocks, and the corresponding variance is derived. The estimation is carried out using Kriging in the presence of a trend, also known as Universal Kriging. Results from soil resistance (NSPT) show the usefulness of this methodology for mapping geotechnical attributes, and consequently, a significant improvement in the quality of projects can be foreseen.