Illustrative educational model with chosen dimensions and materials, not an engineering design, capacity certification, code-compliance check or safety recommendation. Uniform centered contact on sandy gravel, whose presumptive allowable bearing pressure is 3,000 psf (143.6 kPa) in IBC 2021 Table 1806.2. Above that pressure the model treats the footing as settled; it does not predict how far. No groundwater or reinforcement design.