Numerical Simulation Of Load-bearing Characteristics Of Composite Pile Foundation With Vertical Loading

In the traditional design conception of pile foundation, piles bear all of the loads transferred from structure, soils between piles nearly do not bear any loads, so, the bearing characteristics of soil are neglected inconsciently. The safety of this conception has come to a certain demanded, but the design of pile are obviously conservative, and cause resource waste to some extent. Especially with the development of high building in the city, underground space has been utilized efficaciously, so the depth of composite pile foundation become much more deeper and the soil around foundation have some effect on it. Although some of the pile foundation design methods have began to consider the loading characteristics of foundation soil and came to make use of the loading capacity of soil between piles, the improvement of ultimate bearing capacity of soils caused by overload around foundation are not come into consideration. Consequently, the study on optimum designs of composite pile foundation are required expressly. In order to analyse the effects of all kinds of parameter for load-bearing characteristics of composite pile foundation, this paper expounds the theoretical research of capacity, settlement and load distribution in piles and soils, builds up numerical simulation models by FLAC3D finite-volume computer code, and analyses the load-bearing characteristics of composite pile foundation in details.(1)The paper changes the parameters properties of soils and piles, analyses the different parameters effects for foundation settlements, load distribution in piles and soils and piles bearing capacities.Under the vertical loading, the upper loads are undertook by piles in the foundation at the beginning, when the upper loads exceed the sum of ultimate capacity of singe pile, loads begin to be transferred to soils, from this moment, the capacity of soils start to take into effect, and then the interaction of pile-soil are realized veritably. And in process of loading, the loads on the top of piles transfer from corner piles and lateral piles to central piles continuously until all the loads of piles come into equilibrium.The changes of soils parameters in composite pile foundation have more influence on ultimate capacity of soils and on foundation settlement than the capacity of piles. Changes of piles parameters mainly influence capacity of piles and improve ultimate loading capacity of piles, especially the changes of pile length obviously influence settlement deformation, not the capacity of soils.(2)The paper simulates load-bearing characteristics of composite pile foundation on effect of overload around foundation and analyses different pile lengths and pile spaces effects for foundation settlement and loads distribution in piles and soils, then arrive at some conclusion:The overloads around foundation could improve ultimate capacity of soils between piles efficiently and reduce the settlement of foundation. With an increase of pile spaces, loads distribution of soils increase gradually. On a certain effect of upper overload, the increase of pile lengths can reduce foundation settlement obviously. The longer the pile lengths are, the lower settlement is. As long as the effects of upper overload, pile length and pile space are considered in the optimization of composite pile foundation, the settlement of foundation and engineering cost will be reduced to an extent, and a favorable economic benefits will come into an achievement.