Comparison Between 3D FEM Analysis with Static Load Test Data of Downhole Dynamic Compaction: A Case Study of Ground Improvement Works on Volcanic Soils, East Java, Indonesia

The first ground improvement using DDC method in Indonesia was carried at Dhoho Kediri Airport project where the soil at the area is volcanic rocks which consists of volcanic breccia. It is difficult to determine DDC pile parameters based on laboratory tests due to the oversized materials of DDC. Static load test takes a role to ensure that the performance of the DDC pile is satisfactory and back analysis based on static load test can determine DDC pile parameters in design. Back analysis on DDC pile is commonly done by employing finite element method under axisymmetric condition (assuming a unit cell model). However, the unit cell model is it assumed that the DDC no other DDC pile surrounding the tested DDC pile. Such condition is not always applicable. In this paper, 3D finite element model is carried in order to evaluate the effect of using unit cell model on non-uniform arrangement of trial test. The result shows that unit cell model provides very conservative DDC parameters compared to 3D model.