Question

In a valley curve, a descending gradient of 1 in 60 is meeting an ascending gradient of 1 in 75. The total length of valley curve is ________ m. Assume design speed as 75 kmph and rate of change of centrifugal accleration is 0.6$m/s^3$

• A. 42.52

Answer 1

The correct option is A 42.52
Given, Design Speed, V = 75 kmph

= $\frac{75}{3.6}m/s$

= $20.83m/s$

Deflection angle, $N=|n_1-n_2|=|\frac{-1}{60}-\left(\frac{1}{75}\right)|$

= $|-0.03|=0.03$

Rate of change of acceleration for valley curve,

$C=0.6m/s^3$

Hence, length of valley curve

$L_V=2\sqrt{\frac{N{V}^3}{C}}=2\sqrt{\frac{0.03\times {20.83}^3}{0.6}}$

= 42.52 m