The Comparative Eperimental Study On Mechanical Properties Of The Different Aspect Ratios Bored Piles With Post-Grouting To Bottom

Bored pile technology has many advantages, which can increase the carrying capacity and cut down the settlement and so on. It has been applied to high-rise buildings, large span bridges. At home and abroad, many researchers do many study on them, scientific research focuses on construction technology, mechanism of action and the carrying characteristic and so on. But there is few researchs about the carrying characteristic of different length-diameter ratio pile-end post-grouting pile. In the design and construction of post-grouting pile, we often encounter the problems about different pile length and different pile diameter, it is a importance scientific problem that how to choose the suitable pile type. And we should think about that if it impact on the project cost and the construction period. So we should study on different length-diameter ratio pile-end post-grouting pile which has importance practical utility and scientific significance.Aim at these problem, this article relies on the experiment of the pile foundation project of Zhengzhou City 107 cars quick engineering. We should study on the displacement, the carrying capacity, pile lateral friction, tip resistance and the bearing ratio of them, and the pile-soil relative displacement. We also analyze the carrying properties of the different length-diameter ratio pile-end post-grouting pile by utilizing the numerical simulation, and dissect the influence factor such as pile length, pile diameter. The conclusions may be arrived through the research and analysis.(1)In comparison with the pile with big length-diameter ratio, the pile with small length-diameter ratio can get command of the settlement better under the same load, bear more loads in the same settlement, and have more flexible working space. We can find that the pile axial force with small length-diameter ratio change moderately along the depth, and the distribution form of axial force is relatively stable, the vertical transfer ability is stronger. It explain that the load-carrying property of the pile with small length-diameter ratio is much stronger.(2) When the relative displacement reaches a certain degree for pile and soil, the upper pile-side fiction resistance of the pile with small length-diameter ratio increases progressively smaller and tends to be stable. If the relative displacement rises up, the lower pile-side friction resistance increases with it, and the growth trend presents sclerosis type. The pile with big length-diameter ratio gives full play to the upper pile-side friction resistance, but the exerting degree of the lower pile-side friction resistance is much smaller than the pile with small length-diameter ratio. It appears a softening phenomenon that happen to the pile with big length-diameter ratio, and it can make a dent in the carrying property.(3)The tip resistance of the pile with small length-diameter ratio can play more under the same load. At the beginning of the load, it plays faster. There is a delay phenomenon about the tip resistance of the pile with big length-diameter ratio. When the displacement rises up in the end, the tip resistance increases with it. And the growth trend presents sclerosis type.(4)If we add the pile diameter, the pile will fortify the carrying capacity. However it exist the most suitable pile diameter, when pile diameter is greater than optimal pile diameter, the growth of the limited bearing capacity will slow down.(5)If we add the pile length, the pile will fortify the carrying capacity. However it exist the most suitable pile length, when pile length is greater than optimal pile length, the growth of the limited bearing capacity will slow down. Compared with the change of pile length, changing pile diameter has a more significant influence.