3-D FEM Analysis On The Settlement Characteristics Of Inclined Piles Under Inclined Loadings

With the rapid development of China’s infrastructure, there appears more and more large, special buildings, such as arch structures, bridge structures, offshore oil platform, TV tower and transmission lines, etc., whose foundations need to suffer larger inclined loadings. Therefore, the pile foundation is usually set as inclined piles so as to endure larger inclined loadings. At the same time, due to various reasons, a large number of inclined piles are produced during the construction of pile foundation. Because of more complicated working characteristics and bearing mechanism of the inclined piles than that of the vertical piles when subjected to loadings, it is incomplete to understand the working mechanism of the inclined piles and still lacks the reliable and practical analysis and calculation methods, which limits the application of inclined foundations and the dispose of the engineering accidents in many situations.In order to further understand the working characteristics of inclined pile under inclined loading, this dissertation analyzed the working characteristics and settlement influence factors of the inclined single pile and battered pile foundation using finite element method. The main contents and conclusions are as follows:(1) A brief introduction on the research status and main results of inclined piles at home and abroad, the basic ideas of finite element and problems needed to be paid attention during the numerical modeling analysis of the pile-soil interactions, etc., are discussed.(2) The settlement characteristics and its influence factors of the inclined single pile are simulated and analyzed under inclined loadings using finite element software Adina8.4. The calculation results indicate that:①At given parameters, such as pile materials, pile length, etc., the effect of pile inclination on the settlement is smaller than that of the vertical pile in a certain range of inclination angle.②Under inclined loadings, it is not better for larger inclination angle and the top settlement of the pile is not minimal when the angle of loading agrees with that of the pile.③Under vertical loadings, the location of the equilibrium point of the horizontal stress of the inclined pile is related with the factors such as the value of the loading, the inclination angle of the pile, etc. If other conditions remain unchanged, to strengthen the equilibrium point of the pile body can effectively improve the bearing capacity of inclined pile.④The pile body of the inclined pile will produce reverse bending deformation when subjected to inclined loadings. If the inclination angle of the loading agrees with that of the pile body, the reverse bending deformation is minimal.⑤The factors, such as pile length, pile diameter, material property of pile and soil around pile, etc., have much effect on the pile top settlement, of which the effect extent is related with the value of loading.(3) The effect of inclination angle of load and pile body, pile length and pile diameter, etc., on the pile top displacement in the multilayered soil is analyzed using finite element software. The numerical results indicate that:①When the inclination angle of the loading is much smaller (for example,5°), the pile top displacement increases with the increase of inclination angle of pile body in certain range of inclination angle of loading. When the inclination angle of pile body agrees with that of the loading, the pile top displacement is minimal.②When the inclination angle of loading is10°, the top pile displacement is not minimal if the inclination angle of loading agrees with that of the pile body. As for what value of the inclination angle of the pile body to assure the minimal value of the pile top displacement, it depends on the factors of typical engineering geology and loading value, etc..③When the inclination angle of the loading is15°, the displacement is not smallest when the inclination angle of the loading is in accordance with that of the pile body, but when the inclination angle of the pile body is slightly smaller than that of the loading.④When the inclination angle of the loading is much smaller, the inclined pile can be set with its inclination angle consistent with that of the loading. If the inclination angle of the loading is much bigger, the pile top displacement is the smallest if the inclination angle of the pile body is slightly smaller than that of the loading, of which the optimal inclination angle of the pile body needs to be further confirmed based on other conditions.⑤When the inclined loading acting on the inclined pile, it is better to resist the loading and correspondingly to reduce the pile top displacement by changing the length of the pile than changing the pile diameter if the soil of the pile bottom is better.(4) The effect of the battered pile set in the pile group on the bearing capacity and settlement characteristics under inclined loadings is analyzed using finite element methods. The results indicate that:①The pile rigidity, soil properties, the number of inclined pile, pile length and its inclination, etc., are the main factors that affect the inclined pile group settlement under the inclined loading.②In range of30°of the angle of inclined pile, the bigger the inclination angle of the pile is, the smaller the center settlement of the cushion cap is when the inclination angle of the inclined loading is30°.③The center settlement of the cushion cap changes obviously when the angle of inclined pile is between10°and20°but if the inclination angle is bigger than20°, the effect of the inclination angle on the settlement is relatively smaller.④The bigger the pile stiffness and the better the soil are, the smaller the top settlement of the cushion cap is. Affected by the injection depth of pile in the bearing stratum, the effect of soil modulus of bearing stratum on the settlement is smaller, while the modulus of the soil around the pile has much effect on the settlement.⑤Under the inclined loadings, the longer the inclined pile length is, the smaller the center settlement of the cushion cap is. But with the increase of the pile length, the settlement of the inclined pile group changes little.