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Analytical Chem Soil HW Solutions 35

# Analytical Chem Soil HW Solutions 35 - indicate a reducing...

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35 Q3.5 Solution The hydraulic gradient is calculated as the head difference between the manometer tappings Δ h (mm) divided by the distance between them (l = 120 mm). The processed data are given in Table Q3.5 and plotted in Figure Q3.5. Flowrate q, mm 3 /sec 2000 3000 4000 5000 6000 Head difference Δ h, mm 18.8 31.0 45.1 60.0 75.0 Hydraulic gradient i 0.157 0.258 0.376 0.500 0.625 Table Q3.5: Processed permeameter test data Figure Q3.5: Flowrate q against hydraulic gradient i The graph of flowrate against hydraulic gradient is curved convex upward, indicating a permeability that decreases as the flowrate is increased (the gradient of the graph is A.k and, as the cross sectional area of the sample A is a constant, the gradually reducing slope must
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Unformatted text preview: indicate a reducing permeability). This is because as the downward flowrate is increased the sample is compacted (evidenced by the reducing sample height), decreasing both the void ratio and the permeability. The maximum permeability is with the sample in its loosest state, with the sample height z = 180 mm and the flowrate q = 2000 mm 3 /sec. Then k = q/Ai = 2000 mm 3 /sec ÷ (8000 mm 2 × 0.157) ⇒ k ~ 1.6 mm/s The minimum permeability is with the sample in its densest state, with the sample height z = 160 mm and the flowrate q = 6000 mm 3 /sec. Then k = q/Ai = 6000 mm 3 /sec (8000 mm 2 0.625) k ~ 1.2 mm/s...
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