Soil Mechanical Potential Mapping in Construction of Forest Roads Using GIS

Forest roads play a vital role in management, conservation and restoration of forests in mountainous regions. Despite of their costs, forest roads are essential for forest resource management. Recognition of soil properties has a critical role in finding the potential of the ground as base for road construction. Due to expenses of soil analysis, reducing soil samples to its minimum are of great importance in assessment of soil mechanics in forest roads. In this research, based on properties such as soil, slope, aspect, altitude, etc., zonation of study area was done into homogenous units based on landform using GIS. After preparing landform map, one soil sample and totally 32 samples were taken in units from which road passes. Then soil physical properties such as normal moisture (%), bulk density and soil texture were analyzed. According to the soil zonation map, 10 zones were obtained. One sample was taken in each zone and soil mechanic experiments and soil Classification carried out according to USCS method. Results show only 30% of the samples are coarse soil and the others are fine soil. 40% of fine soil have clay fine soil. Hence, in the parts of the road which have Liquidity Index more than one soils have to be drained before road construction and in the parts that soils have high Plasticity Index the road Bed have to be stabilized with lime after excavation. For decreasing costs of road construction and maintenance it is preferable that road cross from areas that are stable and have sustainable soils. To achieve this goal soil mechanical potential mapping has been done.