Question

Question 5 The sketch below shows a right-angle grade-separated intersection of a high-speed railway system and a cambered 2-lane rural road. The over road bridge has a soffit elevation of 604.090m and its centreline (CL) is positioned to correspond with the PVI of sag curve. PVC chainage = 1374.486 PVC elevation = 600 m Curve length (L) - 182 m CL a G1 = -4% G2 = + 6% 5.6 m PVT PVC Not to scale PVi (4) (11) (3) (2) 5.1 Determine the chainages and elevations of PVI and PVT. 5.2 Calculate the available vertical clearance for the rural road (Hint: check the vertical clearance at points a and b). 5.3 Determine the chainage where the storm water catch pit must be provided. 5.4 Determine if 80 km/h is an appropriate speed for this road section. 5.5 Compute the Stopping Sight Distance (SSD) for this underpass section (assume drivers' eye height = 1.8 m and dangerous object height is 0.15 m). (2) [22 Marks] [Total Mark = 100]

Answer 1

solution: Given data chamage of puc = 1374-486m Elevation of puc (Epuc) = 600m Length of curve (2) curve (2) -. 1827 9,= -4%. 92=67. Elevation of briche soffit = 604.090m - 6.1) Chainage of puI = chainage of puc +4/2: 13743486 + 182/2 ::Chainage of PUZ 1465.486m Elevation of pu I = Elevation of pic + (91x 42) - 600+ ( X182 Elevation of PU I = 596.36m chainage of put = chainag e of pub + 42 1465.486 + 18/2 1556.486m :.. Chainage of put Elevation of put = Elevation of putt (92842] 596.36+ ( Elevation of put 있 6 100 182 2 601.82m

xx² 100 Similcurly, 29 = +5.6 (5.2) Elevation of vertical curve at any distance 'x' measured from puc is given as (92-91) Ex = Epuc t9ixt 24 (6-(-41) = 600-4 xx+ -(1) a for point la is given as, ;. Exá = 600 -0.04X85.4 + 100X2X182 Ex = 600-00042 + 0.05 182 x NOW, 182-5-6 L-5.6 Xa= 2 2 ka= 5.85.4m 0.05 182 (85.4)? Exa = 598.588m Clearance at a = 604.09-5981588 : clearance at a = 5.502m 182 2 +5.6 2.96.6m in Exb = 600-0.04x96.6 + 0:05 182 *96:62 Enb = 598.70m

i Clearance at 'b' = 604.09-598.70 Clearance at 'b' 5.39m (63) Storm water catch has to be provided at me lowest point for which distance from puc is given as a lowest : 9.1 91-92 XL --4 -4-6 X 182 allowest = 72.8m chainage of Cowest point - chainage of Pic + acow 13740486 +72.8 chainage of storm water catch 2.1447.286m (5.5) stopping sight distance is): Assume, SCL La As? (12h1 + 2hz)? 60-Grad where , Az 92-9, 6 2 A=001 h, 2 1:87 h2 = 0.15m

342.224 = 3.675 U + U2 .. from the above equation 182. 0.1 XS (1281-8 +V 2X0:15 51? s = 104:31m <i cok) Stopping sight distance = 104.31m U? (5.4) S = 1.470€ + 1.075 x where a = llo2 ft./su } assumed t = 2.5 sec 1 104.31x 1 = (1.47 XUX25] +1.675 x video 03048 10.4186 uz + 3-6750-342,224 10.4186 0 = 43.574 mph = 43.5614X1.609 kmph V = 70.1 kmph speed of 80 kmph is mõie man the design speed of 70.1 kmph. Hence it is not appropriate