07-Bld-A6 Geotechnical Materials and Analysis — National Exam, December 2017. Closed book, 3 hours; drawing instruments and either a Casio or Sharp approved calculator required; the formula sheet and influence charts printed at the back of the exam are reproduced/used inline where needed. Section A (Questions 1–3, 40 marks, answer all) and Section B (Questions 4–7, 20 marks each, the paper asks for any three of four) — all seven questions are answered below.
Reference texts: B. M. Das, Principles of Geotechnical Engineering, 9th ed. (phase relations, seepage/flow nets, stress distribution, consolidation, shear strength); R. F. Craig / J. Knappett, Craig's Soil Mechanics, 9th ed. (flow nets, effective-stress strength parameters); Canadian Foundation Engineering Manual (CFEM), 4th ed.
Check — assumptions and source notes for this paper. (1) Question 4's flow net (Nf = 5 flow channels, Nd = 14 equipotential drops, point A read as three drops upstream of the downstream exit, exit-field length ≈ 2 m) is used with a soil total unit weight of 20 kN/m³. (2) Question 5(ii)'s "approximate" method is extended from the formula sheet's centre-of-rectangle formula to a corner point (point A here is not centred on the loaded area) using the standard mirror/quartering superposition trick, valid because the approximate formula is linear in load exactly like the exact one. (3) Question 6's least-squares fit through the three effective-stress points gives an intercept of −0.7 kPa — not distinguishable from zero with only three data points — so c′ is taken as 0, consistent with the expected behaviour of a normally consolidated clay. (4) Question 7's figure shows three distinct layer thicknesses — H1 = 1.5 m (sand above the water table), H2 = 1.5 m (sand below the water table), H3 = 2 m (the clay layer, void ratio e = 0.75) — and all three values are used below.
