34 the pore water presure acting on the base (A. γ w .[z+h crit ]) begins to exceed the weight of the block of soil (A. .z): A . w .[z+h crit ] = A. .z z ( γ - w ) = w .h crit or i crit = h crit /z = (- w )/ w (main text Equation 3.33) In the present case, we will assume = 2 w giving i crit = 1. At a hydraulic gradient of 1 in upward flow, the flowrates are given by the relevant permeability × the cross sectional area of the sample, 112 mm 2 . For test 1, q crit = 6.3 10-3 mm/s 112 mm 2 = 79 mm 3 /sec (parallel to the laminations) For test 2, q crit = 2.6 10-4 mm/s 112 mm 2 = 3.3 mm 3 /sec (perpendicular to the laminations) (These answers are slightly different from those given in the main text). Q3.5 The following data were obtained from a constant head permeameter test in downward flow on a sample of medium sand. Measured flowrate q, cm 3 /s 2.0 3.0 4.0 5.0 6.0 Head difference between manometer tappings Δ h, mm 18.8 31.0
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This note was uploaded on 12/28/2011 for the course CHM 4302 taught by Professor Stuartchalk during the Fall '11 term at UNF.