Analytical Chem Soil HW Solutions 41

Analytical Chem Soil HW Solutions 41 - Westfield College]...

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41 The analysis would be invalid for drawdowns below the top of the aquifer (datum level) because the flow would become unconfined. The saturated thickness of the aquifer would no longer be constant, and flow would no longer be purely horizontal and could not be represented by a two-dimensional flownet in the horizontal plane. Unconfined flownet Q3.9 Figure 3.43 shows a cross section through a long canal embankment. Explaining carefully the conditions you are attempting to fulfill, estimate by means of a flownet the rate at which water must be pumped from the drainage ditch back into the canal, in litres per hour per metre length. Describe qualitatively what might happen if the drain beneath the toe of the embankment became blocked. [University of London 2nd year BEng (Civil Engineering) examination, Queen Mary and
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Unformatted text preview: Westfield College] Q3.9 Solution The conditions that must be fulfilled in drawing the flownet are equipotentials and flowlines cross at 90 elements in the flownet have the same breadth as length, forming curvilinear squares impermeable boundaries and the centreline are flowlines u = 0 on the top flowline, i.e. the x m equipotential intersects the top flowline at x m above the datum for the measurement of head (phreatic surface condition for an unconfined flownet) The flownet is sketched on Figure Q3.9. The phreatic surface condition is satisfied by trial and error, along with the rest of the conditions above. Note: capillary rise effects are neglected. Figure Q3.9...
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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.

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