Field study on the reinforcement of collapsible loess using dynamic compaction

The dynamic compaction (DC) method is an effective ground treatment technique that is widely used for a variety of soil types and conditions, particularly in loess areas. However, DC is rarely applied to ground where thick collapsible loess is present. The conventional DC method exerts an energy level of no more than 5000 kN·m. Although the DC for collapsible loess treatment is increasing, the use of higher energy inputs for similar soil conditions is quite limited. In this paper, dynamic compaction with a maximum energy level of 12,000 kN·m was applied to a collapsible loess site in the city of Qingyang in the Gansu Province in northwestern China. Field tests were conducted to determine the optimum DC operational parameters. The field studies included deformation tests, standard penetration tests (SPT), static penetration tests and plate load tests. The deformation tests included the crater depth per drop and the whole test zone elevations before and after DC. The standard and static penetration tests and plate load tests were performed to evaluate the final effect of DC. The collapsibility was also measured before and after DC. The allowable ground-bearing capacity and the depth of improvement at the site after treatment achieved no less than 250 kPa and 10 m, respectively, and the collapsibility was greatly reduced or was completely eliminated.