Research Progress On The Project Behavior Of Pile Under Oblique Pullout Loads

The pile with branches and plates is the recent development of a new type of pile. The pile with branches and plates has a high carrying capacity , good solid embedded and more economical characteristics ,so it has a wide range of applications. According to comparative test Single-plate pile bearing uplift capacity is 2.5 times the pile straight, and its more than 15 percent of the amount of concrete, we can see that pile of sticks is a very substantial economic benefits,while the amount of concrete is more than 15%. This shows that the economic benefits of pile is very impressive.Much research has been done about the performance of compression strength of piles presently, while little is about the oblique uplift resistant performance of piles. This paper introduces the pile with the characteristics of the construction process and through the loading angle were 0°(vertical up), 30°, 60°of such diameter piles, pile supported single plate (plate located in the pile body, bottom), double disk branch pile model tests research the status quo,model testing and ABUQUS finite element analysis software in the oblique pile loads bearing capacity and the load transfer mechanism.The results showed that the diameter piles with tilt angle increases will decreases its pullout capacity as the key of diameter of pullout capacity is to provide friction pile, with the load inclination increase just increases the horizontal load will lead to pile side of the trend of pile-soil separation, so that the side of the pile-soil friction reduction or loss, although the other side of the pile-soil contact surface pressure will increase friction, but some of the increase in friction is very limited.For the branch pile, although the load angle will reduce the pullout capacity, but compared to the diameter pile the loss will much smaller, while experimental results show that the pile is not the load the greater the inclination pullout capacity of the smaller, such as the 60°angle when the pullout capacity rather than the 30°angle , which meant pile pullout capacity is the capacity of the disk from the control function. The results also proved that the oblique uplift resistant capacity of branch pile is far higher than the corresponding diameter piles.As to diameter piles, the pile-soil effect is main from uplift frictinon and lateral pressure under oblique loads, pile-soil load transfer is relatively simple. In addition to the branch pile friction and lateral pressure are set to pass the proliferation of surrounding soil pressure, soil around the piles to increase the loading area, compare to diameter of pile ,branch can provide much bearing capacity, which is also an important reason that branch pile capacity can be improved. At the same time the oblique loading to branch at the horizontal and vertical directions around pile soil generate two different loading and unloading,so the pressure changes of soil (the load transfer) has become more complicated.