Determination of the most Important Factors of Pavement Demolition of Forest Roads in Azar Roud Watershed

Road construction operation in the forest is one of the most important cost factors in the field of forest management. The most important part of the construction of a road is its pavement, and the highest cost in the section of road completion and restoration is related to the cost of pavement. Therefore, the focus of management studies and planning is more in this sector. The aim of this study is identified of the effective factors in the destruction of forest road pavement in order to reduce the costs of forest road repair and maintenance in Azarrood sub-basin located in Savadkoh city in Mazandaran province.

For this purpose, 139 samples (with dimensions of 10.5 * 5.5 meters) were selected from the first-class forest roads in the series, then the physiographic variables of the area, the geometric shape of the forest roads and the grading of pavement materials were measured in each sample. In order to measure the pavement deterioration, the parameters of the volume of potholes, the volume of longitudinal grooves, the amount of stone protrusion surface and the volume of transverse grooves or shutters were measured. The relative importance of each of the pavement failure parameters was determined based on the process of hierarchical analysis and using experts' opinions. To model and determine the effect of each of the independent variables, two methods of multiple linear regression and random forest model were used.

The modeling results showed that the random forest method with an explanation factor of 89% compared to the linear regression method with an explanation factor of 28.4% had better results in modeling and analyzing the effects of variables on forest road pavement damage. Also, the results showed that in both modeling methods, the longitudinal slope of the road and the percentage of clay and granularity of road pavement materials are the most important factors in the damage of the entire road pavement.

In general, the results showed that the damage of the whole road was directly related to the increase in the size of the aggregates and the increase in the length of the tangent. Therefore, it is suggested to select the type of materials more carefully during the road construction operation and consider them in the road design.