roadwaydesign.com

Unpaved Roads with Geogrid Reinforcement - Design Calculator

 
Problem Statement
This calculator utilizes design methods proposed by Giroud - Noiray (1981), and Giroud - Ah-Line-Bonaparte (1985), in conjunction with the properties of geogrids.  This interactive calculator is developed allowing one to compute the required aggregate thickness of all unpaved roads with a geogrid reinforcement.  The use of geogrid reinforcement in unpaved road applications can result in a reduction in the aggregate thickness, and for extreme soft subgrade, geogrids make it feasible to build the initial construction platform.

Unpaved Cross Section

The design procedure of unpaved roads is calculated in the following five steps:

  1. Calculate the required aggregate thickness, h'0 for the unreinforced road with traffic.
  2. Calculate the required aggregate thickness, h0 for the unreinforced road with a single passage of traffic using a quasi-static analysis.
  3. Calculate the required aggregate thickness, h for the reinforced road with a single passage of traffic using a quasi-static analysis.  An iteration scheme is necessary in order to solve h.
  4. Calculate the reduction of aggregate thickness, Dh due to the inclusion of geogrids.
  5. Calculate the required aggregate thickness, h' for the reinforced road with traffic.

where

Symbol Description Unit
e distance between midpoints of two sets of wheels m
N number of traffic passages (max=10,000)
P single axle load kN
r allowed rut depth m
Cu undrained shear strength of the soft subgrade kPa
Pc tire inflation pressure kPa
k tensile modulus of geogrid kN/m

 
Input Values
          
Distance between midpoints of two sets of wheels (e) m           
Number of traffic passages (N) N           
Single axle load (P) kN           
Allowed Rut depth (r) m           
Undrained Shear Strength (Cu) kPa           
Tire Inflation Pressure (Pc) kPa           
Tensile Modulus of Geogrid (k) kN/m           
Type of trucks           


          

References
Giroud, J.P. and Noiray, L. (1981) "Geotextile-reinforced unpaved road design", Journal of Geotechnical Engineering, ASCE, 107, 1233-1254.

Giroud, J.P., Ah-Line, C. and Bonaparte, R. (1985) "Design of unpaved roads and trafficked areas with geogrids", Proc. Symp. on Polymer Grid Reinforcement in Civil Engineering, pp. 9-12, London

Hausmann, M.R. (1987) "Geotextiles for unpaved roads - A review of design procedures", Journal of Geotextiles and Geomembranes, 5, 201-233.

Holtz, R.D. and Sivakugan, N. (1987) "Design charts for roads with geotextiles", Journal of Geotextiles and Geomembranes, 5, 191-199. 

Copyright 2001 Advanced Geotech Systems.  All rights reserved.