6 The vertical total stress σ v = 19.99kN/m 3 × 0.4245m = 8.486kPa. Hence the vertical effective stress ' v = v- u = 8.486kPa - 4.164kPa ⇒ ' v = 4.322kPa (c) In the dense, saturated state, the weights of water and soil grains above the base do not change. Hence the pore water pressure and the total stress are the same as before, and so also is the effective stress: u = 4.164 kPa; ' v = 4.322kPa (d) The water level in the column does not change: as the sand is densified, it settles through the water. The new sample height h' is given by its volume, 1130cm 3 , divided by the cross-sectional area of the measuring cylinder, 28.27cm 2 , giving h' = 39.972cm. The depth of water above the new sample surface is therefore (42.448cm - 39.972cm) = 2.476cm. The pore water pressure at the new soil surface is 9.81kN/m 3 0.02476m u = 0.243kPa The effective stress at the sand surface is zero. Particle size analysis and soil filters Q1.6 A sieve analysis on a sample of initial total mass 294g gave the following results:
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