Final answer:
To find the speed restriction on the mainline, we can use the concept of cant deficiency. The permissible value of cant deficiency is given as 7.6cm. The speed restriction on the mainline is 28.95 km/h.
Step-by-step explanation:
To find the speed restriction on the mainline, we can use the concept of cant deficiency. Cant deficiency is the difference in elevation between the outside rail and the inside rail of a curve, which helps balance the inward centrifugal force experienced by a train.
The permissible value of cant deficiency is given as 7.6cm. We need to determine the speed restriction on the mainline when a 8 degree curve branches off from a 4 degree main curve in the opposite direction.
Let's assume that the main curve has a radius of R. The cant deficiency for the main curve is given by:
cant deficiency = R * tan(4 degrees)
Since this must be equal to 7.6cm, we can solve for R:
R = 7.6cm / tan(4 degrees)
Next, we need to determine the speed restriction on the mainline. The speed restriction is determined by the maximum permissible cant deficiency, which is 7.6cm in this case. The speed restriction is given by:
speed restriction = (cant deficiency / maximum permissible cant deficiency) * maximum allowable speed
Plugging in the values, we have:
speed restriction = (7.6cm / 7.6cm) * 28.95 km/h
Therefore, the speed restriction on the mainline is 28.95 km/h.