| Current trend has shown that farms are getting fewer, but farm size is becoming larger and larger. As the farm size is getting larger, the farm equipment is simultaneously becoming larger to adapt the new state and federal regulations which encourage farmers to store manure as a liquid and apply it in a short time period. The sizes of farm as well as farm equipment are growing faster than both the pavement design technology and the state regulations. The effect of such an increase on pavements would be an accelerated rate of pavement deterioration. There is a concern that the heavy farm equipment can do significant damage to pavement and bridges.;Initiated in early 2007, this study used a comprehensive series of combinations of farm equipments, axle load, speed and traffic wanders to determine the pavement response under various types of farm equipments and to quantify the pavement damage due to various agricultural equipments. Two typical instrumented concrete testing pavement sections were used to measure the critical pavement responses and validate the theoretical pavement response model ISLAB 2005.;Through this research, it was determined that traffic wander, seasonal effect, pavement structure, and vehicle type/configuration have pronounced impact on pavement responses. However, traffic speed is not statistically significant with respect to pavement performance. Additionally, all agricultural vehicles tested generated higher pavement responses than a standard semi-truck when they are fully loaded. It is also found that if the rear axle of the agricultural vehicles is driven 18--24 inches (2 feet) away from the pavement shoulder, the pavement damage could be reduced to minimal even when they were fully loaded. The study also found that by increasing concrete pavement thickness by 2.5 inches, the pavement strain response will be reduced as much as 280%.;ISLAB2005, a finite element program, was utilized to perform the damage analysis for different pavement structures under various agricultural vehicles with and without slab curling behavior. The damage analysis results confirmed the field behavior that all agricultural vehicles introduce higher pavement responses than a standard semi-truck. The damage analysis also concluded that the damage due to slab curling coupled with heavy agricultural vehicle's loading could be devastating for the concrete pavement.;The findings of this study is expected to provide a better understanding of the interaction of farm equipment with the pavement structures which will facilitate more rational regulation of Spring load restrictions, additionally with respect to acceptance of new designs and innovations in vehicle configuration. The findings will help highway agencies to design roads that are more capable of resisting to damage related to heavy loading with complex gear configuration. |
