PASSABILITY CRITERIA FOR UNPAVED ROADS ( The experience of an operational road engineer guided by research findings ) PRESENTATION BY MARTIN HMENSA DEPARTMENT OF FEEDER ROADS, GHANA. OUTLINE OF PRESENTATION. Assumed degree of engineering of unpaved roads. - PowerPoint PPT Presentation
Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.
PASSABILITY CRITERIA FOR UNPAVED ROADS(The experience of an operational road engineer guided by research findings)PRESENTATION BY MARTIN HMENSADEPARTMENT OF FEEDER ROADS, GHANA
CBR ≤ 10% (?)
CBR >10% (?)
CBR > 35% (Ghanaian specification)
Materials with 10% < CBR< 35% - Underestimated strength.
C2 = 0.0138 (N 0.175 )(P 0.580 )(Q0.490 )
C2 = soaked CBR of roadbed soil, in percent
N = the number of passages to failure
P = equivalent single wheel load, KN
Q = tyre inflation pressure, KPa
Failure criterion : 75mm rut depth.
Education of heavy truck drivers required:
I. To check deterioration
ii. To reduce road maintenance cost
iii.To avoid blockage of roads
32% reduction in tyre pressure of heavy trucks can increase the life of an earth road by 3 times.
SFCBR ≥ 8.25 + 3.75 * log (ADT)
SFCBR = the soaked CBR at standard Proctor Laboratory compaction (600KJ/M3) in percent
ADT = the average daily vehicular traffic in
both directions, in vehicles per day
Log is logarithm to base 10
Log HG = 1.40 + 12.3 CI –0.466 C2– 0.142 NE 0.124 RDC – 0.5
Replace the co-efficient 12.3 by 0.856 P 0. 235Q0.285 where the wheel load P and the tyre pressure Q are significantly different.
L = Length of road improved or maintained in km
C = the cost of an activity in appropriate currency.
T = Time period over which the road remains improved or satisfies a minimum specified criterion.
20% <CBR< 40% do not require gravelling