Question

A trapezoidal masonry dam with vertical upstream face is 4.6 m high, 0.5m wide at the top and 3m wide at the base. Hydrostatic uplift varies from full hydrostatic pressure at the heel to zero at the toe. Find the depth of water if the pressure at the toe is twice the average pressure at the base. Wt. of masonry is 2,400 kg/m3 Find the height of water that could rise behind a rectangular masonry wall 2m thick and 5m high without causing an intensity of pressure at the toe greater than twice the average pressure of the base. Assume sp. gr. of masonry as 2.4. USA 3 لادنا = النا14 A trapezoidal dam having a top width of 0.60m and a bottom width of 1.2m is 1.8 m high. The depth of water on the vertical side of the dam is 2.4 m. Determine the max and min pressure at the bottom of the dam. Neglect the effect of water on the inclined sides.

Answer 1

40.6m 4.6m. P W2 1/3 rwn Given; wt. of mastory Masonry = 2400 kg/m3. = 23.5 kN/m² Now, weight W, = rxv = 23.5 x 4x(3-06)X 46 X1 Weight W₂ = 129. 72 KN. rxv 0.6x4.6618 23.5 64.86 KN. twice the average Now, given pressure at toe = pressure at base Average pressure at Base= uplift pressure 47 upto which water U VwHXB : stored. 2 Total uplift acts at Bl, Sw- 9.810 kN/m3. → e = 2 B ł 2 1.5 -1 = e = 0.5m.

Now, pressure at toe = p = Ev (it be Ev= Wit W₂ - U So, EV 2xU B According to given condition pressure at toe 2x Average pressure (+) (it be -u ( 1+ 6x05) = WitW₂-u 2u B 2U V 129.72 + 64.86 - U 3 7 194.58-U E U 4U= 194.58 3 끼 U= 48.645 Now, putting the value of u; VWBH 48.645 7 9.810X BOXH 48.645 2 → H - 48. 64582 9.8183 3.3058 m Ans.