Transportation Engineering (Mar 2022)
Performance of labor-intensive base course for gravel roads with application of Do-nou
Abstract
Community participation in road construction and repair is necessary in improving rural roads in developing countries, more than 50% of which are in poor condition caused by less involvement by the government due to budget constraints. To promote community participation, constructing base course with do-nou, the Japanese term for soil bag, which does not require the use of compaction equipment, has been proposed as a practical method. To extend the application of this method, the method must be adopted by stakeholders and its performance must be clearly understood. In this study, to compare the performance of the base course constructed with do-nou with that of the conventional structures constructed with equipment based on the existing manual for low-volume roads, a series of full-size model driving tests were conducted. Silty sand with gravel was selected as the base course material that is locally available and can be practically used in rural areas of developing countries. The deformation of the base course reinforced with do-nou under traffic loading was 14.0%. By contrast, the deformation for the base course compacted with equipment was 4.9% and that for the base course compacted manually without reinforcement with do-nou was 20.9%. The results of a dynamic cone penetration survey revealed that encapsulating the base course material in do-nou bags efficiently converted the traffic load into compaction energy and thus developed a balanced strength profile. Base course reinforced with do-nou behaved as an aggregate of distinct elements of do-nou and transferred a smaller load to the subgrade when subjected to traffic loading compared with nonreinforced base courses compacted manually and with equipment. The base course with do-nou and manual compaction did not perform as well as the base course compacted with equipment; however, it demonstrated intermediate performance with surface settlement of less than the maximum allowable level of 50.8 mm. The thickness of the base course reinforced with do-nou can be determined according to the existing design manual. The degree of compaction of base course constructed labor-intensively is initially insufficient. Therefore, once the road is opened to traffic, traffic should pass over the entire width of the road in dry conditions to accelerate compaction and improve road performance.
