Soil Mechanics/Geotechnical Engineering

A: Governing principle: Ultimate end bearing in dense sand scales with bearing capacity factors times effective stress, not material strength. Applied here: dense sand toe resistance is often taken as a few MPa; pile area is ~0.28 m², giving low single-digit MN. Option B traps engineers who over-anchor on overburden stress alone and forget the bearing factor amplification.

A: Governing principle: Pumping needs free water plus repeated loading to mobilize fines. Applied here: rainfall, shoulder location, and traffic-induced deflection point to saturated subgrade with poor drainage. Option C catches engineers focused on structural capacity while missing the hydraulic trigger.

A: Governing principle: Compaction acceptance ties in-situ density and moisture to a defined lab reference at a controlled lift thickness. Applied here: thickness controls compaction energy effectiveness; testing after that check avoids false passes. Option D attracts engineers used to production metrics instead of acceptance criteria.

A: Governing principle: Immediate settlement in clay can be approximated with elastic solutions using footing width and modulus. Applied here: 150 kPa × 2 m / 8 MPa gives a few times 10 mm, not negligible. Option C traps those mixing time-dependent consolidation with immediate response.