PIV Analysis of the Ground Behavior at Pile Tip by Vertical Load Test of Model Piles with and Without Expanded Bottom as a Variable.

In evaluating the vertical bearing capacity of cast-in-place concrete piles, there are many findings for straight piles, but few for expanded bottom piles. Since the group pile effect is a phenomenon in which adjacent piles interact with each other through the ground, it is important to understand the behavior of the ground during loading, which may be affected by the pile geometry near the pile tip. In this study, the behavior of the ground at the pile tip during vertical loading tests of a single pile and two piles in a group was investigated based on the results of PIV analysis using a pressurized tank test apparatus that can observe the ground behavior, with the parameters of the overburden pressure and pile shape. The results showed that the distribution of vertical and horizontal displacement of the ground between the piles varied depending on the overburden pressure, pile geometry, and pile spacing because oblique downward ground displacement occurred from the corner of the pile tip surface regardless of the pile geometry, and the ground inside the group pile interfered with each other.