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Geotechnical Engineering Exam 1
Water content, w - correct answer Ww/Ws (0 to 200%) Degree of Saturation, S - correct answer Vw/Vv (0 to 100%) Unit Weight, gamma - correct answer W/V (62.4 pcf or 9. kN/m3 for water) Mass Density, rho - correct answer M/V = gamma/gravity (1000 kg/m3 for water) Total (wet) Unit Weight - correct answer Wt/Vt = (Ws + Ww)/(Vs + Vv) = (1+w)*(dry unit weight) =Gs(1+w)(unit weight of water)/(1+e) Dry Unit Weight, gamma d - correct answer Ws/V (60 to 125 pcf) Saturated Unit Weight, gamma sat - correct answer (Ws + Ww)/V , Vair = 0 (90 to 140 pcf) ((Gs + e)/(1+e)) (Unit Weight of water) Specific Gravity of Solids, Gs - correct answer Ws/Vs * 1/unit weight of water (2.6 to 2.8) Void Ratio, e - correct answer Vv/Vs (0.2 to 5.0) n/(1-n) = (Gs(unit weight water) / Unit Weight dry) -
Porosity, n - correct answer Vv/V (0.2 to 0.9) e/(1+e) Gsw = - correct answer Se Fines - correct answer Smaller than the #4 sieve Coarse - correct answer Everything retained on the #4 sieve % finer than d2 = - correct answer 100 * (wpan + w4 + w3)/Wt Best shape of soils for good strength? - correct answer Angular!! Roughest, sharpest, best shear strength Terminal Velocity, vs - correct answer Effective depth / elapsed time Gradation curve - correct answer Grain size (x axis), percent passing or percent finer (y) Well-graded soil - correct answer Linear gradation curve, slight s shape, good amount of every size of soil. Most ideal soil Uniform/poorly graded soil - correct answer Majority if the soil is in a narrow range of size. Creates a vertical part of the curve Gap-graded soil - correct answer Sample is missing a range of soil size, creates a horizontal part of the curve. Can have lots of fines and lots of gravel, but not a lot of medium size. Easy for the fines to get swept away Plasticity - correct answer Ability of soil to undergo unrecoverable deformations at a constant volume without cracking or crumbling
O - correct answer Organic H - correct answer High Plasticity L - correct answer Low Plasticity Coefficient of Uniformity, Cu - correct answer Cu = D60/D Coefficient of Curvature, Cc - correct answer Cc = (D30^2)/D60*D Hand Augers - correct answer Low cost, portable, can only go so deep Test Pits - correct answer Need space, very expensive, easy to do and not much time required Standard Penetration Test, SPT - correct answer Slow, lots of equipment, relatively expensive, collects real samples, produces lots of information, not repeatable Cone Penetration Test, CPT - correct answer Fast, less equipment, repeatable data, needs interpretation, does not produce real samples, not good in gravel Vane Shear Test - correct answer Used only for soft clays, measures shear strength Dilatometer - correct answer Has to be measured in the field, measure of pressure/force it takes to dilate the knife thing
Bernoulli' Theorem - correct answer Total head, h = elevation head + pressure head + velocity head (velocity head is negligible Total head = - correct answer Z + U/(unit weight of water) Open standpipe piezometer - correct answer High compliance, good for sands Pressure transducer peizometer - correct answer Low compliance, good for clays Q - correct answer Flow rate m3/s Discharge velocity, V - correct answer Flow rate / area of cross section = Q/A Hydraulic Gradient, i - correct answer Change in head / distance between points = (delta h)/L V = - correct answer -ki (Darcy's law) Seepage velocity, Vs - correct answer Discharge velocity / porosity = V/n K - correct answer Hydraulic conductivity Constant Head HC Test - correct answer K =Q(delta L) / A(delta h) Falling Head HC Test - correct answer K = al*(ln(ho/h1)) / At Teton Dam - correct answer Failure caused by:
Soil Consolidation - correct answer Removal of water (saturated conditions), time dependent (not instantaneous) fast for sand, slow for clay Purposes of soil compaction - correct answer Increased shear strength Improved quality control Increased stiffness Improved erosion resistance Decreased hydraulic conductivity Decreased liquefaction potential Lower void ratio - correct answer Denser soil Dry unit weight calculation - correct answer Gamma d = gamma t / (1 + w)
