Finite Element Analysis Of Super-Long Bored Piles

With the development of super-long buildings, it is necessary to massly use super-long piles because of their high bearing capacity. Though a large number of super-long piles have been used, its load-transfer mechanism is not distinct. By now, its design method still adopts that of the ordinary piles, which disagrees with practical situation. The design method of super-long pile in the applicable codes and standards is not based on the mechanism of load-bearing and deformation. Therefore, the research on the load-bearing properties and the reasonable design method of the super-long piles is important to meet the requirements of the theory and the reality.Therefore, in this paper, based on the other research works, the three-dimensional non-linear finite element calculation technology is adopted to study the load-transfer mechanism of super-long piles and find out the different properties between super-long piles and ordinary piles. Furthermore, with a project example,by the ANSYS, the three-dimensional simulation model have been founded. The influence of the modulus of piles, pile-length and pile-diameter on the load-bearing properties, including the relation of settlement and load, the characters lateral friction resistance, axial force, and pile compression, are analyzed.Based on the result of the non-linear finite element analysis, some conclusions and suggestions are also proposed. Results indicate:1. The lateral friction resistance and the bottom resistance of pile displays asynchronously, and the former displays at the first. The lateral friction resistance displays asynchronously in different soil layers, and the upside soil layers achieve ultimate bearing capacity at the first , then the lower gradually achieve ultimate bearing capacity under the increasing load.2. The scene test pile material and the value simulation analysis indicate that the strengthened effect of side resistance displays near the pile toe when the pile-length hasn't surpassed certain length .3. For the super-long pile, the bottom resistance of pile can't display entirely because the settlement of the pile toe is very small when the settlement of the pile top attains control value. It indicates that supporting capacity of the super-long pile determined according to traditional methods isn't accurate because the bottom resistance of pile can't display entirely under ultimate load.4. When designing a super-long pile, supporting capacity of the super-long pile can't be enhanced effectively by increasing purely pile-length when the pile-length has surpassed certain length because the settlement of the pile top has already possibly met control value.5. For the super-long pile, pile-diameter should be determined suitably for playing its role fully. But with the pile-diameter increasing, the amount of the concrete and the construction cost can increase obviously. Therefore, to the super-long pile, we should consider each kind of factors and choose the appropriate pile-diameter and the pile-length reasonably.