Soil Bearing Capacity Analysis Quick Reference Guide

Soil bearing capacity quantifies the ultimate pressure a soil mass can sustain before catastrophic shear failure occurs, typically modeled using limit equilibrium theory and empirical correlations. The analysis distinguishes between ultimate bearing capacity (qu), the theoretical maximum load intensity at failure, and allowable bearing capacity (qa), which applies appropriate safety factors (typically 2.5–3.0 for general loading, higher for dynamic or uncertain conditions) to qu to account for uncertainties in soil parameters, modeling assumptions, and consequences of failure. Key influencing factors include soil type (cohesive vs. cohesionless), unit weight, shear strength parameters (c and φ), foundation dimensions (width B, depth Df), embedment level, shape and orientation of the foundation, and groundwater table position — all of which modify stress distribution and failure surface geometry. Standard analytical methods include Terzaghi’s original bearing capacity equations for strip, square, and circular footings; Meyerhof’s generalized method incorporating shape, depth, and inclination factors; and Vesic’s refinement accounting for soil compressibility and rigidity. Modern practice often supplements these with numerical modeling (e.g., finite element analysis) and in-situ testing (SPT, CPT, plate load tests) to calibrate input parameters and validate predictions.