Vegetation Tests of Geocell-Reinforced Unpaved Shoulders

To accommodate heavy truck loads, geosynthetic has been used as reinforcement to stabilize unpaved shoulders. However, while the geosynthetic changes the strength of the shoulder, it may also influence the vegetation that is planted on the shoulder. To study the effect of geosynthetic reinforcement on vegetation, outdoor vegetation tests were conducted. The primary method was to compare the growth of vegetation, mainly perennial ryegrass and tall fescue, on different mixes of soil at the same thickness with and without geosynthetic reinforcement. Geocell reinforcement was used in this study. Different base course and topsoil combinations were investigated, including: 50-mm-thick turf soil over 100-mm-thick aggregate; 50-mm-thick turf soil over 100-mm-thick soil-aggregate mixture (50% aggregate); 50-mm-thick turf soil over 100-mm-thick soil-aggregate mixture (65% aggregate), and 150-mm-thick soil-aggregate mixture (50% aggregate). Each test section was 1.5 meters long and 1.5 meters wide. During the test, soil moisture content, soil temperature, and precipitation were measured. To evaluate the vegetation growth, grass blade height, number of flowers and number of blades were recorded periodically. The effect of geocell inclusion on the vegetation was evaluated as compared with the vegetation without geocell.