Geotechnical Engineering and Foundations
Geotechnical questions emphasize site investigation, soil classification, and the selection of foundation type. Candidates must understand the phases of investigation (desk study, preliminary, detailed), the meaning of standard penetration and cone penetration tests, and how groundwater conditions affect design. Know the difference between total and effective stress, the principle of effective stress, and how pore pressure governs consolidation and bearing capacity.
For shallow foundations, understand bearing capacity theory, settlement (immediate and consolidation), and the distinction between allowable and ultimate bearing capacity with a factor of safety. For deep foundations, grasp pile capacity components (shaft and base resistance), group effects, and negative skin friction. Retaining structures require knowledge of earth pressure at rest, active, and passive states, and drainage details.
Traps
A frequent trap is applying total stress analysis where drained conditions govern, or vice versa. Another is ignoring the water table in bearing-capacity and slope-stability calculations. Questions about liquefaction test whether you recognize loose saturated sands under cyclic loading. Slope stability questions often hinge on recognizing the critical slip surface and the role of pore pressure.
Rule of thumb
Apply a factor of safety of about 3 on ultimate bearing capacity for shallow foundations under service loads, and always verify settlement separately-capacity alone does not guarantee serviceability. For piles, capacity is the sum of shaft friction and end bearing, reduced for group interaction.