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16-Civ-B3 Geotechnical Design: December 2019

Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)

  1. Question 1 Critical height of an unsupported cut in saturated clay
  2. Question 2 Improving the factor of safety of a failing slope
  3. Question 3 When to design on undrained strength, and how to measure it
  4. Question 4 Expansive clay as retaining-wall backfill
  5. Question 5 When a mat foundation is preferred
  6. Question 6 Width of a square footing on normally consolidated clay
  7. Question 7 Design axial capacity of a belled drilled shaft
  8. Question 8 Overturning stability of a gravity retaining wall
  9. Question 9 Schmertmann settlement, and ten more storeys

Start with Question 1 →

Paper format. National Examinations, December 2019 — 16-Civ-B3 Geotechnical Design. Three hours, open book, any non-communicating calculator. Section A holds five discussion questions worth 7 marks each (answer any four); Section B holds four design questions worth 24 marks each (answer any three). The examinable total is therefore 4 × 7 + 3 × 24 = 100 marks. Page-1 Note 3 sets the answer-any-four / any-three rule, and Note 6 requires the candidate to name the source of every design chart and of every assumed value — so every chart read, correlation and assumption below is attributed where it is used. All nine questions are solved here, because the set is a study resource rather than a timed sitting.

Reference texts. B. M. Das, Principles of Foundation Engineering, 9th ed. (bearing capacity, elastic settlement, retaining walls, drilled shafts); B. M. Das, Principles of Geotechnical Engineering, 9th ed. (shear strength, lateral earth pressure, slope stability); Canadian Geotechnical Society, Canadian Foundation Engineering Manual (CFEM), 4th ed. (Canadian practice, factors of safety, in-situ testing); R. F. Craig, Craigʹs Soil Mechanics, 9th ed. (effective stress, undrained strength); D. P. Coduto, Foundation Design: Principles and Practices, 2nd ed. (shallow-foundation design, settlement serviceability).

Check — conventions used throughout this paper. Unit weights printed on the figures are treated as bulk (saturated below any water table); effective unit weights use γw = 9.81 kN/m3. Reinforced concrete is taken at γc = 24 kN/m3 (CFEM 4th ed.; the exam gives no value), and Question 8 shows that the conclusion is unchanged anywhere in the 23–25 kN/m3 range. Where the paper omits a number the solution needs, the assumption is stated at the point of use and its influence on the answer is quantified, as page-1 Notes 1 and 7 invite.