Geometric design of rural roads Design Brief: Design speed: 80 km/h Terrain: typically clay with some localised sandstone Horizontal curve radii: Curve 1 (chainage 60 to 200) 260 metres Curve 2 (chainage 420 to 600) 240 metres Curve 3 (chainage 870 to 1100) 230 metres Drainage structures: Chainage 90 – 1 x 900 mm diameter pipe Chainage 562 – 2 x 1200 mm diameter pipes Chainage 1000 – 1 x 900 mm diameter pipe Maximum depth of fill = 6.5 metres Maximum depth of cut = 5 metres Minimum cover over drainage pipes = 1.25 metres Design standard: Austroads Guide to Road Design Part 3 -Geometric Design 2016 and the relevant Roads and Maritime Services NSW Supplements Cross section: Pavement width 7.0 m (2 x 3.5 m lanes) Shoulder width 1.5 m Verge 1m in fill (allowing for safety barrier) 2.0 m in cut (includes table drain) Table drain 2.0 m wide, 1:4 slope Batter slopes 1:1 in cut 2 (h): 1 (v) embankment Maximum grade 7% Minimum grade 1% Maximum superelevation 7% Minimum superelevation 3% Crossfall on straights 3% Assignment requirements: 1. Horizontal Design a. Design the superelevation required for the three horizontal curves. b. Design the superelevation development (using rate of rotation criterion), the plan transition and the shift (if needed) for the 230 metre curve (870-1100). c. Draw the cross sections at chainages 900 and 940 using the attached cross section sheet. The cross sections show the natural surface levels. At chainage 900, the assumed design level at the centreline is 289.48. At Chainage 940, the assumed design level is 291.10. On the cross sections show the dimensions of the lanes, the shoulders, verge and shift. 2. Vertical Design a. The attached PDF shows the plan of the road and the long section of the natural surface. What are the control points, what are the target levels at the control points and why? b. What are the k values for the crests and the sags. c. Select trial grades between the control points and select vertical curves which meet the k value criteria. Show how the grades and the length of vertical curves meet the requirements for minimum k values. Note that the start and finish the design levels at the existing levels at chainages 00 and 1180. The only drawing required is for the two cross sections. Marks will be deducted for sloppy, untidy and unprofessional work. Students must prepare their own original designs. Identical grading designs are not to be submitted. Take note : As long as the realignment design is there, that is all that is needed
