Geotechnical Engineering Expert

Before Starting

1. Foundation design or slope stability?
2. Shallow or deep foundation?
3. Sand or clay soil behavior?

Core Expertise Areas

Soil Classification

USCS: unified soil classification system, grain size and plasticity-based. Grain size: gravel, sand, silt, clay based on particle size distribution. Atterberg limits: liquid limit, plastic limit, plasticity index for fine soils. Relative density: measure of sand compactness, Dr = e_max minus e over e_max minus e_min. Compaction: Proctor test determines optimal moisture content for maximum dry density.

Shear Strength

Mohr-Coulomb: tau_f = c plus sigma prime tan phi, cohesion plus friction. Drained vs undrained: sand drains fast, clay drains slow under load. Effective stress: sigma prime = sigma minus u, pore pressure reduces effective stress. Triaxial test: measure shear strength at different confining pressures. SPT and CPT: in-situ tests correlate to strength and stiffness parameters.

Consolidation

Primary consolidation: volume change from pore pressure dissipation in clay. Terzaghi theory: cv dU over dz2 = dU over dt, diffusion of excess pore pressure. Settlement calculation: delta = Cc times H over 1 plus e0 times log sigma_f over sigma_0. Time rate: T_v = cv times t over H2, use time factor chart. Secondary compression: creep settlement after primary consolidation complete.

Foundation Design

Bearing capacity: Terzaghi and Meyerhof equations for shallow foundations. Net bearing pressure: gross minus overburden pressure. Pile capacity: end bearing plus skin friction, static and dynamic methods. Group effects: pile group efficiency, settlement of pile groups. Mat foundation: uniform pressure distribution, used on weak or variable soils.

Best Practices

• Always conduct adequate site investigation before foundation design
• Use conservative soil parameters given natural variability
• Check both bearing capacity and settlement for shallow foundations
• Consider groundwater effects on effective stress and stability

Common Pitfalls

Pitfall	Fix
Ignoring differential settlement	Check settlement variation across structure footprint
Wrong drainage condition for clay	Use undrained strength for short term, drained for long term
Underestimating secondary compression	Account for creep in organic soils and soft clays
Missing groundwater in slope stability	Pore pressure dramatically reduces factor of safety

Related Skills

• structural-engineering-expert
• hydraulics-expert
• geology-expert