Study On Pile's Lateral Nonlinear Dynamic Response Under The Horizontal Seismic Action

Single pile's lateral non-linear dynamic responds under the horizontal earthquake action has been studied in the paper. First of all, we used finite element method software ANSYS, considering material nonlinearity of soil and the interface state nonlinearity of pile-soil, established a three-dimensional finite element model. The model has considered the pile and soil's finite element choice, the soil boundary simulation, the dimension of mesh, the method for input of the earthquake wave, and the gravity load of system, then statics and dynamics test having been in progress to the model, in order to prove the correctness of the geometry model. Secondly, we used this model, inputted earthquake motion, under two kinds of calculation patterns: the constant damp and the Rayleigh damp, calculated the lateral responds of free field and single pile-soil system. At last, with this finite element model, this dissertation gave a relatively complete analysis to the lateral seismic nonlinear dynamic responses of the single pile, and analyzed the pile head's response spectrum, earthquake Fourier's spectrum, then a test parametric sensitivity analysis was taken into consideration, including modulus ratio of pile to soil, soil material damping ratio, earthquake input level. At the same time, we established the finite element simplified program for the dynamic interaction of single pile-soil foundation, the p-y curve of single pile under monotonic loading was used as the skeleton curve, and then used the three dimensional finite element models to confirm the accuracy of simplified model. At last, we used this simplified model, calculated the pile head's response spectrum and time history under different input earthquake levels, and provided the reference for the actual project. Based on the analysis above, the main achievements are follows:1. The result analyzed in free field indicates soil layer could enlarges the acceleration which input from the bedrock, and compared with elastic soil, the plasticity soil is larger in the displacement, velocity and acceleration, this illustrate the material non-linear characteristic of soil has a certain influence to the earthquake of the free field.2. Considered soil's elastic-plasticity and whether the interface of the pile-soil are separated, the result of calculation showed material non-linear characteristic of soil body and state non-linear of pile-soil's interface haven a certain influence to the single pile's horizontal earthquake. Considered that this two nonlinearity factors, these could more accurate description to the single pile's lateral earthquake response. 3. Compared with free field, after setting up a pile body, the displacement, velocity, acceleration of pile head are obviously reduced, this proved that the existence of pile arrived the effect of reducing the earthquake effect.4. When the earthquake happening, the greatest dynamic response of pile appeared on the pile head or top part.5. The calculation results indicate that the pile soil stiffness ratio is the most sensitive one among pile-soil stiffness ratio,soil material damping ratio and earthquake design level.