Soil Mechanics-Based Geotechnical Mapping of the Rae Bareli Area for Urban Foundation Planning

A comprehensive geotechnical map of the Rae Bareilly region in the Middle Ganga Plain was developed through systematic soil mechanics investigations to assess subsurface characteristics and foundation suitability. Soil sampling was conducted yielding a total of 90 samples, including 15 undisturbed and 75 disturbed samples. Laboratory analyses of in situ samples comprised determination of natural moisture content (NMC), bulk density, specific gravity, grain size distribution, sedimentation characteristics, direct shear strength parameters, free swell index, Atterberg limits, shrinkage limit, and pH. Disturbed samples were tested for specific gravity, grain size distribution, sedimentation, free swell index, Atterberg limits, shrinkage limit, and pH. Based on these parameters, twelve thematic geotechnical maps were generated to represent the spatial variability of soil engineering properties. Soil classification was performed using gradation curves for coarse-grained soils and the liquid limit–plasticity index chart for fine-grained soils, supported by triangular textural classification. The results indicate predominantly high natural moisture content and moderate density across the region. Textural analysis reveals dominance of silt and silt loam soils, with minor occurrences of sandy and clayey facies. Plasticity assessments classify most soils as low-plasticity clays and silts (CL, ML, and CL–ML), while clay activity analysis indicates largely inactive soils with localized medium to high activity zones. Shear strength parameters show cohesion values between 0.03 and 0.45 kg/cm² and internal friction angles from 10° to 37°. The study concludes that well-graded sandy soils are favorable for foundation construction, whereas expansive clayey soils require careful engineering consideration due to swelling potential.