comparison of effects of polymer material on physical properties of forest road soils

stabilization, alter and improvement of engineering properties of soil are for providing predetermined goals. the most important aim of soil stabilization is increasing long term soil strength, but in very wet and loos lands the other aim of soil stabilization, is to decrease plasticity characteristic of soil, which are tested by atterberg limits tests. since the road soils of namkhane district of kheyrud forest, have fine grained texture, with high clay content and high plasticity, it's necessary to attempt to improve the mechanical properties and stabilize the soil, before road construction work starts. nowadays with new technologies, polymer materials have been released. in the present study, compaction and atterberg limits tests on samples of natural soil and treatment soils with different percentages of 2 types of polymer material cbrplus and rpp were studied. also due to determine the effect of time on performance of  these polymer material, samples treated with 0.05% cbrplus  and 0.03% rpp prepared, stored for 7 and 14 days and then atterberg limits  tests were conducted on these samples. result showed that with the addition of difference percentage of cbrplus to soil, liquid limit was changed between  3.27 and  22.05 and plastic limit was changed between 0.94 and 6.97. the plasticity index decreased between 4.8 and 32.5. adding rpp decreased the liquid limit between 4.93 and 14.27, plastic limit between 3.14 and 8.57 and plasticity index between 13.22 and 24.03.the results of atterberg limits indicate that add this material causes improvement of plasticity properties of soil, and treatment time technical has no significant influence on plasticity properties of soils. also results of compaction test indicate that add cbrplus to soil, increase maximum dry density between 1.58 and 9.85 and optimum moisture between 3.57 and 23.21. adding rpp, somewhat (0.75 and 1.58%) improve the maximum dry density of soil. it has no effect on optimum moisture. generally according to achieved results, add this material to soil cause relative improvement of soil characteristics.