Two large diameter steel cased drilled shafts (TS-1 and TS-2) were installed and load-tested with the maximum load of 2000 ton at the Kwang-An grand bridge. One of test shafts (TS-1) was socketed into the fresh rock and the other test shaft (TS-2) was socketed into the weathered rock. Most loads were carried by the weathered rock layer at the maximum applied load for the test shafts. In additions, numerical studies were performed using PENTAGON 3D and ROCKET. Based on this study, the weathered rock layer provided excellent side resistances and possibility of an alternative embedded layer if weathered rocks are deeply layered over fresh rock, which caused difficulties and cost in construction.
Usages of large diameter drilled shafts with socketed in rock are being increased due to their ability for resisting large superstructures. The selection of foundation for the Kwang-An grand bridge was also a large diameter rock socketed drilled shaft. The geological formation of the Kwang-An grand bridge has wide depth range of weathered rock over-layered fresh rock layers. The original design concept of the large diameter rock socketed drilled shaft was socketed and embedded on the fresh rock. However, the design was modified to socketed and embed on the weathered rock due to difficulties of construction penetrating through deep weathered rock layer. In order to verify the axial behavior of rock socketed large diameter drilled shafts embedded into the weathered and fresh rocks at the Kwang-An grand bridge, small scaled test shafts were constructed.
Total of two test shafts were installed at the Kwang-An grand bridge. One of test shafts (TS-1) was socketed into the fresh rock and the other test shaft (TS-2) was socketed into the weathered rock.