Behavior of vertical and lateral load on T-Shape barrette and bored piles

The large diameter long bored piles are commonly used as foundation for high-rise buildings and bridges in Bangkok, Thailand. However, in case of high loading capacity requirement in the limited area, the use of barrette pile foundations would make a better alternative to bored piles. Generally, the main load component of pile foundation is vertical loading. For some structures, piled-foundation might be designed to resist the high lateral loading. The T-shape barrette pile is, therefore, proposed to be an alternative deep foundation not only to support vertical loading but also to resist high lateral loading. The pile under vertical and lateral loading is the soil-pile interaction problem which concern to many parameters in both structure and soil properties. Therefore, the selected parameters for analysis and design pile size, pile length and number of piles in footing must be considered with allowable load, allowable settlement and movement of soil and piles. In this research, The full scale static pile load tests were conducted to verify the vertical and lateral load capacities of T-shape barrette and bored piles with pile tip founded in the second dense silty sand layer about 55 m depth below ground surface. The analyses were performed using PLAXIS 3D Foundations, the 3D Finite Element Method (FEM) Program. The test results show that the shear plane is not positioned along the T-shape barrette shaft perimeter under vertical loading. For piles under lateral loading, apparently, possible concrete cracking in the FEM analysis of the pile significantly affects the calculated results of both T-shape barrette and bored piles. If concrete cracking effect is neglected in the numerical analysis, the results tend to overestimate the pile capacity. For the design approach, the back analysis suggests that input soil stiffness for T-shape barrette should be about 3 times of empirically calculated value for bored pile to predict deflection values before concrete cracking. Besides, that the flexural stiffness of T-shape barrette should be decreased by approximately 70% to obtain the lateral movement after concrete cracking.