Question

3) (a) Plot the vertical effective stress with depth along section A-B Figure 2. (b) If the river level were to rise by 2 ft, would the vertical effective stress distribution change? Explain your answer. (c) If the river level were to drop by 2 ft, how much would the vertical effective stress at B change? River 8tt iver bed Soft clay 20ft | T 105-pcf Sand Yat 110 pctf

Answer 1

Total stress sigma = r_w times 8 = 62.4 times 8 = 499.2 Psf (pound per sq.ft) Pore pressure mu = 62.4 times 8 = 499.2 Psf effective stress sigma^bar = 499.2 - 499.2 = 0 At intermediate point (interface sand and clay) Total stress sigma = 62.4 times 8 + 1.5 times 20 = 599.2 Psf Pore Pressure mu = 62.4 times 28 = 1747.2 PsF effective stress sigma^bar = 2599.2 - 1747.2 = 852 Psf At Point B Total stress sigma = 62.4 times 8 + 105 times 20 + 110 times 18 = 4579.2 Psf Pore Pressure mu = 62.4 times 46 = 2870.4 Psf effective stress sigma^bar = sigma - mu = 4579.2 - 2870.4 = 1708.8 Psf \r\n The distribution of effective stress is as. If water level rises by 2 ft then river bed is at 10 ft from top. At A, sigma = 10 times 62.4 = 624 psf mu = 10 times 62.4 = 624 psf