Question

The buttresses of a free deck buttress dam are provided at ‘x’ m clear spacing and buttress thickness is proposed to be ‘t’ m. The buttress section can then be designed like the section of a concrete gravity dam by considering the effective unit weight of water = Surcharge factor (S) x actual unit weight of water. The value of this surcharge factor is given as _____________

(a) S = (x + t)/x

(b) S = (x + t)/t

(c) S = (x + t)/(x + 1)

(d) S = (x + t)/(t + 1)

This question was addressed to me by my college professor while I was bunking the class.

My question is based upon Buttress Dam in division Arch and Buttress Dams of Irrigation Engineering

Answer 1

Right answer is (b) S = (x + t)/t

To explain I would say: Surcharge factor (S) is the ratio of the dam length (x + t) to the buttress thickness (t).

S = (x + t)/t

The resultant impact can be considered by increasing the unit weight of water by multiplying the actual value by a surcharge factor.