Effectiveness of Variable Tire Pressure for Control of Distress on Roads with Thin Asphalt Surfacing Layers and Peat Soil Subgrade

A forest access road pavement with peat soil subgrade and thin (50 mm) asphalt surfacing layer, was instrumented to verify the effectiveness of Variable Tire Pressure technology for control of surface distress resulting from timber haulage traffic. Distress potential was evaluated with respect to longitudinal and lateral interfacial strains under the surfacing layer, and normal stress on the subgrade due to a timber haulage truck. Results indicate that the lateral strain due to the steering wheels determine initial failure of the surfacing layer, while longitudinal strains control the subsequent degradation, and an empty truck (4 tonnes per axle) with high tire inflation pressure (770 kPa[110 psi]) will induce as much fatigue cracking of the pavement as a fully laden truck (9 tonnes per axle) at low (350 kPa[50 psi]) tire inflation pressure. Trucks with tire pressure control systems such as Central Tire Inflation may therefore improve the bearing capacity (number of wheel passes sustained before pavement serviceability is impaired) of such pavements. Stress on the subgrade (potential for pavement rutting) reduced with decreasing axie load, but was significant at uneconomic payloads.