Vol.:(0123456789) 1 3 Environmental Earth Sciences (2021) 80:413 https://doi.org/10.1007/s12665-021-09720-5 ORIGINAL ARTICLE Application of Kriging for development of SPT N value contour maps and USCS‑based soil type qualitative contour maps for Islamabad, Pakistan Muhammad Hamza Khalid 1  · Badee Alshameri 1  · Usama Abid 1 Received: 23 November 2020 / Accepted: 24 May 2021 / Published online: 31 May 2021 © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2021 Abstract Geotechnical maps provide preliminary knowledge of sub-surface parameters which help in hazard identifcation, plan- ning of detailed investigations, mitigation measures, and design for engineering projects. Maps consisting of zones with generalized stratigraphy for an entire area provide uncertain information which may lead to overlooking subsurface geo- technical hazards. In contrast, continuous contour plots consider spatial variation with depth. The purpose of this paper is to make efcient SPT N-value digital maps and soil type maps classifed using Unifed Soil Classifcation System (USCS) that indicate N value and soil type at unsampled locations in Islamabad, Pakistan. The geostatistical Kriging approach is unprecedently applied to Islamabad (Pakistan) to develop the contours. The proposed methodology involves integrat- ing geotechnical data with contouring software Surfer 18. Data from ffty geotechnical investigation reports were used to create contour plots of twelve soil types and SPT N values at 3, 5, 10, 15, 20, and 25 ft depth intervals. In addition, a map indicating the depth of groundwater was also developed. The geotechnical contour maps presented in this paper are the frst of their kind for Islamabad and lie consistent with geological generalizations of the region. A coefcient of correlation of 0.88 was found for SPT N-values. The output will serve as a supplement for site characterization and hazard identifcation for future projects. Keywords Geotechnical mapping · SPT N values · USCS soil classifcation · Kriging · Qualitative contours · Surfer 18 · Site characterization Introduction Subsurface conditions play a signifcant role in the design of geotechnical structures. The first step involved in executing a project is the identifcation of the geologic subsurface. This information can be extracted using con- ventional drilling techniques, geophysical methods, or a combination of both. However, the data is unorganized, not easily accessible, and heterogeneous. Moreover, the data obtained by drilling is costly and poorly archived (Bardet and Zand 2009). Geotechnical engineers address uncertainties by interpolating the limited data (Priya and Dodagoudar 2018). In response creating a readily available spatial geotechnical database is a requisite. Geographical Information and Global Positioning Sys- tems (GIS and GPS) have been revolutionizing the feld of engineering since their inception. GIS can integrate spatial data with graphic visualization, the result of which is a Geotechnical Map. This in turn is helpful in providing a quick and easy interpretation of spatial data. With access to preliminary information, detailed geotechnical investi- gations can be narrowed down to only sensitive projects. The preliminary judgement of soil types and parameters can help plan risk mitigation measures and enhance design capabilities by narrowing down the most suitable solutions based on examples of existing neighboring structures. * Badee Alshameri badee.alshameri@yahoo.com; b.alshameri@nice.nust.edu.pk Muhammad Hamza Khalid mhamzakhalid@hotmail.com; mkhalid.nice@nice.nust.edu.pk Usama Abid usama.abid1997@yahoo.com 1 Department of Geotechnical Engineering, NUST Institute of Civil Engineering (NICE), School of Civil & Environmental Engineering (SCEE), National University of Sciences and Technology (NUST), Islamabad, Pakistan