Reference no: EM13867288

Objectives

This assessment item relates to the course learning outcomes 1, 3 and 4. It develops students' ability to design road geometric elements including roadside drainage.

Details/Questions

On the contour plan shown in attached map, a two-lane two-way road is to be designed for 70km/hr speed joining Pub Road at Point A (CH0+000) and Fun Road at Point B alongside the pond . The design covers route location, horizontal and vertical alignments, cross-sectional elements, earthworks and road drainage design to achieve the most safety and economical outcome. The following are the requirements:

• At Point A, the reduced level of the road is to be RL675.
• At Point B, the reduced level of the road is to be RL675.
• There will be only one horizontal curve and only one vertical curve.
• The truck traffic is negligible. Hence consider only cars for design.
• Radius of horizontal curve [R= LN(student ID)×8.4] is upward rounded to 5m.
• Length of vertical curve [L= (student ID)1/4] is rounded to nearest 5m.
• Side slope of cut is 1:1, fill is 1:2. Shrinkage factor = 10%.
• Uniform ground slope at a particular chainage can be assumed. It can be obtained from contour map by joining two points at two sides of the road centreline, each at 20m distance perpendicular to the road centreline.
• Lane width= 3.3m, sealed shoulder width= 1.2m.
• Normal crossfall is -3% for lanes and -5% of sealed shoulder.
• Rainfall intensity is 60mm/hr ( 1 year ARI) and 120mm/hr (10 year ARI)

Within the constraints described above, design should include the following design elements (note: you cannot finalise these elements in sequence and iterative process is required):

1. Sketch two alternative alignments. Choose one alignment for your design. Justify.

2. Locate your alignment considering both vertical and horizontal controls. Coordinate both horizontal and vertical alignments.

3. Design horizontal alignment (tangents and circular curve- also transition curves if required). Develop a horizontal alignment design table.

4. Design vertical alignment (grades and parabola) in detail. Develop vertical alignment design table.

5. Design superelevation for your road.

6. Design side drain for your road for the runoff accumulated from road surfaces only.

7. Draw an appropriate longitudinal section showing both horizontal and vertical curves.

8. Determine and tabulate the cross section levels (left end of the shoulder, left end of lane, centreline, right end of lane and right end of shoulder) at 20m interval.

9. Draw cross-sections at 40m interval including the side drain.

10. Calculate earthwork quantities using 40m cross-sections over the length of the road (pavement depth can be neglected). Draw mass-haul diagram and discuss the properties of your mass-haul diagram.

11. Check stopping sight distance on horizontal and vertical curves.

12. Check road-ponding/aquaplaning safety