Conceptual Model on the Effect of Axial Load on Shallow Isolated Footings Resting on Clay Soil

This study investigates the geotechnical behavior and bearing capacity of clay soils at the Polo Ground in Maiduguri, Nigeria, with a focus on their suitability for building and shallow structural foundation design. Laboratory tests were conducted on soil samples collected at a depth of 2.0 meters to determine key index properties such as moisture content, specific gravity, Atterberg limits, grain size distribution and shear strength parameters. The results indicated high plasticity indices (PI > 17), classifying the soils as highly plastic clays (CL and CH) under the Unified Soil Classification System (USCS). Specific gravity values ranged from 1.32 to 2.60, suggesting the presence of organic material and further raising concerns regarding the soil's load-bearing capability. The computed safe bearing capacities for the soil samples ranged from 136.9 to 166.4 kN/m2, with an average design value of 152 kN/m2. These results reflect moderate bearing strength, typical of soft clay soils, which necessitate careful foundation design. The settlement analysis conducted for samples A, B, and C revealed settlement values of 196 mm, 291 mm, and 186 mm, respectively. These values are considered significantly high and may pose serious risks to the structural integrity of buildings supported by isolated footings. Excessive settlement of this magnitude can lead to differential movement, cracking, and potential failure of foundation elements, particularly in structures with limited load redistribution capacity. To validate the structural performance on such soils, STAAD Pro Connect software was used to model and analyze isolated footing system under various load conditions. The analysis confirmed that the footing design complies with BS 8110-97 standards, offering adequate load distribution and structural stability under the evaluated geotechnical conditions. This integrated geotechnical and structural analysis approach provides a reliable framework for safe and optimized foundation design in clay-rich soils.