Workmanship and quality control on collapsible loess construction

This paper summaries the construction workmanship of collapsible loess section under Taotong Expressway in Ningxia. Highway subgrade is normally damaged seriously due to deformation caused by collapsible loess resulting from water intrusion. Therefore, it is very important for highways constructed in such kind of topographic area to reduce their collapsibility and void ratio in order to improve the strength and stability of subgrade. Impact compaction method is adopted, which utilizes impact roller with running speed of 12-15km/hour to pass the kinetic energy produced from the running to the ground. With this method, the effective compaction depth can be achieved 1 meter to further reduce the settlement volume and void ratio of soil during the construction and quicken the consolidated settlement. As a result, the settlement of subgrade after its construction is finished in advance and the potential quality defects of traffic are eliminated. First, from the testing data, the paper identifies that the subgrade soil of Taotong Expressway is non weight collapsible loess based on the theoretical analysis on collapsible loess. Then, the paper proposes the improved construction workmanship according to its characteristics and summarizes quite a lot of testing data based on practical experiences and conduct analyses. It proves that it is feasible to adopt impact compaction method to deal with collapsible loess, which would quicken the consolidation and settlement of subgrade earth filling, reduce void ratio and minimize settlement after its construction, and it would provide solid foundation for subgrade, pavement construction and traffic movement in later days.