非均质土层中单桩水平简谐动力响应特性的数值分析

运用土动力学和结构动力学原理,基于改进的Winkler地基梁模型,同时考虑桩侧土的弱化效应和地基土层的成层非均质性,采用数理方程方法分别求解土与桩的振动方程,建立了水平荷载作用下单桩侧向简谐动力响应特性分析的计算力学模型和方法,并将所得结果与有限元计算结果进行对比分析,验证了所提出的计算方法的合理性。通过对影响单桩水平简谐动力响应特性的各相关参数进行变动参数分析,总结出了各影响参数对单桩水平简谐动力响应特性的一般影响规律。

Numerical Analysis on Lateral Dynamic Response of Single Pile Embedded in Layered Non-Homogeneous Subsoil to Harmonic Loading

Because of its high strength, great bearing capacity and fine durability, pile foundation has been widely used in civil construction engineering such as high buildings, large workshops, water and electricity hinges, railways, highroads, bridges, offshore platforms and nuclear power plants. The study on lateral dynamic response characteristics of pile can be sorted into three classes such as elastic continuum methods, beam-on-Winkler foundation methods and numerical methods. Also Tajimi and Novak have reviewed the research advancement of pile dynamics and proposed many questions to be solved. In this paper, a computational method and mechanical model for evaluating lateral dynamic response of single pile embedded in non-homogeneous soil layers to harmonic excitation are established based on a certain assumptions and the improved dynamic model of beam-on-Winkler foundation by using the principle of soil dynamics and structural dynamics. Both non-homogeneity of soil strata and softening effect of soil layer around pile during vibration are simultaneously taken into account in the proposed computational model. Then the comparative study on a numerical example is carried out and the research results indicate that the numerical results of dynamic response of single pile computed by the proposed method are rather rational and can well agree with the numerical solutions gained from the well-known software of finite element method. Finally the parametric studies are conducted for a varied range of main parameters and the following effects of relevant factors on lateral dynamic response characteristics of single pile embedded in non-homogeneous layered soils to harmonic loading with different exciting frequencies are discussed. 1.The lateral displacement of single pile is increasing gradually along with the enhancement of the softening area and the softening degree of soils around pile. 2.The lateral displacement of single pile is influenced by the conditions of soil layers and the influence of upper soil layer is greater than that of the bottom soil layer. So much attention must be paid to the engineering characteristics of upper soil layer in the design and analysis of the lateral dynamic response of pile. 3.The lateral displacement of single pile is not always reduced monotonously along with the increase of slenderness ratio of pile and there is an optimal slenderness ratio. In the illustrated example, the optimal slenderness ratio is 20. 4.The lateral dynamic response of single pile takes on the trend of increase along with the increase of the pile-soil stiffness ratio.In conclusion, the computational method and mechanical model proposed in this paper for evaluating the lateral dynamic response of single pile is rather rational and can be used in the analysis of pile dynamics.