Geotechnical Engineering Exam 1Questions With All Complete Answers And Verified Solutions.

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 9.81 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) -1 Porosity, n - correct answer Vv/V (0.2 to 0.9) e/(1+e) Gs*w = - correct answer S*e 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 Liquid Limit, LL - correct answer Limit in between plastic and liquid. Liquid is too soft. Water content at 25 blows Plastic limit, PL - correct answer Limit in between semi-solid and plastic. Plastic is good. Water content where the soil crumbles Shrinkage limit - correct answer Limit in between solid and semi-solid. Solid is chalky and too dry Atterberg limits - correct answer Do not change with the water content Plasticity Index, PI - correct answer PI = LL - PL Liquidity Index, LI - correct answer LI = (w - PL)/(LL - PL) Activity - correct answer Activity = PI/(percent finer than 0.002 mm), basically clay size G - correct answer Gravel S - correct answer Sand W - correct answer Well graded P - correct answer Poorly Graded C - correct answer Clayey M - correct answer Silty O - correct answer Organic H - correct answer High Plasticity L - correct answer Low Plasticity Coefficient of Uniformity, Cu - correct answer Cu = D60/D10 Coefficient of Curvature, Cc - correct answer Cc = (D30^2)/D60*D10 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: Dam backfill was too dry Fractured bedrock abutments Piping erosion by seeping water Total Vertical Stress, sigma v - correct answer Sigma v = effective stress + pore water pressure = sigma'v + U Pore water pressure, U - correct answer U = Hp * unit weight of water Buoyant Unit Weight, Gamma b - correct answer Gamma b = gamma sat - gamma water Effective vertical stress, sigma'v - correct answer Sigma'v = sigma v - U If pore water pressure exceeds vertical stress, sigma v ( sigma'v 0) - correct answer FAILURE: liquefaction, quick sand, soil particles not in contact with each other Critical hydraulic gradient, i crit - correct answer I crit = buoyant unit weight / unit weight of water I i crit - correct answer Failure!! (Quick condition) Capillarity, hc - correct answer Hc = 4*Ts*cos(alpha) / d*(Unit Weight of water) Ts - correct answer Surface Tension Soil Compaction - correct answer Densification by removal of air, which occurs instantaneously!! 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)