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GATE 2016 CE (CE2) – Question 24

Irrigation · Canals, design of weirs on permeable foundation, cross drainage structures · 1 mark · Multiple choice

Profile of a weir on permeable foundation is shown in figure I and an elementary profile of 'upstream pile only case' according to Khosla's theory is shown in figure II. The uplift pressure heads at key points Q, R and S are 3.14 m, 2.75 m and 0 m, respectively (refer figure II). What is the uplift pressure head at point P downstream of the weir (junction of floor and pile as shown in the figure I)?

Diagram for GATE 2016 CE (CE2) question 24
  1. 2.75 m
  2. 1.25 m
  3. 0.8 m
  4. Data not sufficient

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Show answer and explanation

Correct answer: (B) 1.25 m

Explanation

Both elementary profiles have floor length40m, pile depth5m and total head4m. Reversing the upstream-pile case to the downstream-pile case complements corresponding head fractions. The given floor–pile junction R has head2.75m, so the corresponding downstream junction P has4−2.75=**1.25m, B**.