Paper format. Professional Engineers Ontario /
Engineers Canada National Examinations, May 2015 — 98-Civ-B3 Geotechnical Design.
Three hours, OPEN BOOK, any non-communicating calculator. Section A carries five
discussion questions of 7 marks each (answer any four); Section B carries four design
questions of 24 marks each (answer any three); the examinable total is
4 × 7 + 3 × 24 = 100 marks. All nine questions are worked below, because
the set is a study resource rather than a timed attempt.
Reference texts (98-Civ-B3 / 16-Civ-B3 Geotechnical Design).
- B. M. Das, Principles of Foundation Engineering, 9th ed. — bearing
capacity (Ch. 3), stress increase in a soil mass (Ch. 6), retaining walls (Ch. 8), pile
foundations (Ch. 11), subsurface exploration (Ch. 2).
- B. M. Das, Principles of Geotechnical Engineering, 9th ed. —
consolidation (Ch. 11), shear strength (Ch. 12), lateral earth pressure (Ch. 13).
- Canadian Geotechnical Society, Canadian Foundation Engineering Manual
(CFEM), 4th ed. — the governing Canadian practice document for site investigation,
bearing resistance, deep foundations and earth-retaining structures.
- R. F. Craig, Craig's Soil Mechanics, 9th ed. — earth pressure theory,
effective stress and slope stability.
- D. P. Coduto, Foundation Design: Principles and Practices, 3rd ed. —
in-situ testing, settlement of shallow and deep foundations.
- M. J. Tomlinson & J. Woodward, Pile Design and Construction Practice,
6th ed. — shaft adhesion in clay, pile-group behaviour, load testing.
Sources of design charts and assumed values (page-1 Note 6). Note 6 of
this paper requires the candidate to identify the source of every design chart used and
of every value assumed in the absence of data. They are named where used and collected
here:
- Q6 — bearing capacity factors $N_c$, $N_q$, $N_{\gamma}$ from
Das, Principles of Foundation Engineering, Table 3.3 (Prandtl–Reissner
$N_q$, Vesic $N_{\gamma}=2(N_q+1)\tan\phi'$); shape factors after De Beer (1970) and
depth factors after Hansen (1970), Das Table 3.4. Assumed: unit weight of water
$\gamma_w = 9.81$ kN/m$^3$; general shear failure; the sand extends at least $2B$ below
the base.
- Q7 — adhesion factor $\alpha = 1.0$ for soft clay
($c_u \le 50$ kPa) from NAVFAC DM-7.2 Fig. 1 and Tomlinson & Woodward Table 4.6;
$\lambda = 0.24$ at an embedded length of 12 m from Vijayvergiya & Focht (1972) as
tabulated by Das, Table 11.7; bearing factor $N_c^{*}=9$ for $L/D \ge 4$ (Skempton).
Assumed: pile spacing $s = 3d = 1.5$ m centre to centre, driven closed-end concrete
piles, clay $\gamma_{sat} = 17$ kN/m$^3$ with the water table at ground level.
- Q8 — compression index from the Skempton correlation
$C_c = 0.009\,(LL-10)$, Das Principles of Geotechnical Engineering Eq. (11.42);
$2{:}1$ stress distribution, Das Eq. (6.31); Boussinesq rectangular influence factor
(Das Table 6.6) used as the cross-check.
- Q9 — Coulomb active pressure coefficient, Das
Principles of Foundation Engineering Eq. (8.13) with the wall friction angle
prescribed by the question, $\delta = 0.6\phi' = 18^{\circ}$. Assumed: unit weight of
reinforced concrete $\gamma_c = 24$ kN/m$^3$ (CSA A23.3 nominal); passive resistance in
front of the toe neglected; the backfill surface is horizontal and carries no surcharge.
