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07-Str-A3: May 2016

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

  1. Question 1 Five statements, each to be justified
  2. Question 2 At-rest, active and passive lateral earth pressure
  3. Question 3 Settlement of a structure founded on peat
  4. Question 4 Increase in vertical stress below the corner of a condominium raft
  5. Question 5 Flow net and effective stress at a cut-off wall
  6. Question 6 Angle of shearing resistance from a drained triaxial series

Start with Question 1 →

Paper format. Engineers Canada / PEO National Examinations, May 2016 — 07-Str-A3 Geotechnical Materials and Analysis. Closed book, three hours, 100 marks, one approved Casio or Sharp calculator, drawing instruments required. All six questions are compulsory and are weighted 20 / 10 / 10 / 20 / 20 / 20. The paper carries its own appendix (pages 8–11): a formula sheet, the rectangular-loading m–n influence chart and a Newmark influence chart whose influence value is printed on the formula sheet as $\sigma_z = 0.005\,N q$, i.e. $I_N = 0.005$ over 200 elements. Values quoted below are taken from those sheets.

Reference texts.

  • B. M. Das & K. Sobhan, Principles of Geotechnical Engineering, 9th ed. — Ch. 2–3 (grain size, phase relations), Ch. 6 (compaction), Ch. 7–8 (permeability and seepage), Ch. 9 (stresses in a soil mass), Ch. 11 (consolidation), Ch. 12 (shear strength), Ch. 13 (lateral earth pressure).
  • R. F. Craig / J. A. Knappett, Craig’s Soil Mechanics, 8th ed. — Ch. 2 (seepage and flow nets), Ch. 3 (effective stress), Ch. 4 (consolidation, $C_\alpha$), Ch. 5 (shear strength and the choice of test), Ch. 6 (stress distribution), Ch. 7 (lateral earth pressure).
  • M. E. Harr, Groundwater and Seepage — Ch. 4 (the conformal solution for a single sheet pile in a stratum of finite depth, used here to audit the drawn flow net).
  • Canadian Geotechnical Society, Canadian Foundation Engineering Manual (CFEM), 4th ed. — Ch. 4 (site investigation), Ch. 10 (settlement of organic soils and peat), Ch. 27–28 (lateral earth pressure and support systems). The Canadian reference for practice, sampling classes and terminology.
  • K. Terzaghi, R. B. Peck & G. Mesri, Soil Mechanics in Engineering Practice, 3rd ed. — Art. 16–17 (seepage, piping and the exit prism), Art. 19–20 (shear strength), Art. 25 (secondary compression and $C_\alpha/C_c$).

Check — three readings of the printed paper, carried as stated.

(1) Question 1 is headed “(4 x 5 = 20 marks)” but prints five lettered parts (i)–(v). All five are answered and the header total of 20 marks is kept as printed; the mismatch is a printing slip in the source, not a missing part.

(2) Figure 1 (part (ii)) prints no dimension for the depth of the permeable stratum. The dam base is dimensioned $L = 15$ m and the section is drawn to a single horizontal scale, so the stratum has been scaled off the drawing at $T \approx 5.6$ m ($T/L = 0.37$). The answer to (ii) does not depend on that number — it is read from the printed flow net — but the independent numerical check below does, and the sensitivity is stated where it is used.

(3) In Figure 4 the stem of Question 5(b) says point $A$ is at the “back of the piling”, while the dot is drawn on the upstream (headwater) face of the sheet pile, 1 m below ground. The drawn face is answered, and the value on the downstream face at the same elevation is reported alongside it.