高海拔多年冻土区桩基础选型及有限元分析
发布时间：2019-02-25 20:34
【摘要】：本文根据冻土区输电线路杆塔基础的设计原则和五道梁地区的冻土特性，选择了两种杆塔基础——锥柱基础和预制管桩基础进行现场真型试验。试验分为冻结期和融化期两个部分，每个时期分上拔和水平、下压和水平两种工况进行。通过对桩基础的位移、内力、土侧压力的观测，得到Q～s曲线图和分级荷载下不同断面的轴力图。经过研究分析，发现锥柱基础的承载性能良好，基础选型及设计合理，可用作青海～西藏直流输电线路工程的线路基础。而管桩基础截面规则，侧壁光滑，抗拔性能较差，不能用作上拔荷载较大的输电线路基础。通过试验和理论计算，推导出了适合在风荷载较大的多年冻土地区使用的桩基础极限承载力公式。 由于冻士参数不易从实验中获取，为了采用有限元模型计算，本文运用BP神经网络进行参数反演，得出摩尔库仑本构模型的冻土力学参数值。据此建立了锥柱基础在冻土中的三维有限元模型，得到了锥柱基础在冻土中的竖向和水平位移云图，并与真型试验得出的结论做对比，验证了模型的准确性和适用性。根据有限元模型分析得出：融土深度为2m时，对锥柱基础的下压极限承载力和竖向位移影响较小，，但对锥柱基础的上拔极限承载力和上拔位移影响较大。
[Abstract]:According to the design principle of transmission line tower foundation in frozen soil area and the frozen soil characteristics of Wudaoliang area, two kinds of tower foundation, cone-column foundation and prefabricated pipe-pile foundation, are selected for field test. The experiment is divided into two parts: freezing period and thawing period, each period is divided into two working conditions: up-drawing and horizontal, down-pressure and horizontal. Based on the observation of displacement, internal force and lateral pressure of pile foundation, the QS curves and axial diagrams of different sections under graded loads are obtained. Through the research and analysis, it is found that the cone column foundation has good bearing capacity, reasonable selection and design of the foundation, and can be used as the line foundation of Qinghai-Tibet HVDC transmission line engineering. The section of pipe pile foundation is regular, the side wall is smooth, and the pull-out resistance is poor, so it can not be used as the transmission line foundation with higher uplift load. Through experiment and theoretical calculation, the formula of ultimate bearing capacity of pile foundation is derived, which is suitable to be used in permafrost area with large wind load. In order to use the finite element model to calculate the parameters of frozen soil, BP neural network is used to inverse the parameters, and the mechanical parameters of frozen soil of Mohr-Coulomb constitutive model are obtained. Based on this, a three-dimensional finite element model of cone-column foundation in permafrost is established, and the vertical and horizontal displacement cloud images of cone-column foundation in frozen soil are obtained. The accuracy and applicability of the model are verified by comparing with the conclusion of true test. According to the analysis of finite element model, it is found that when the depth of melted soil is 2m, the influence on the ultimate bearing capacity and vertical displacement of cone column foundation is small, but it has great influence on the ultimate bearing capacity and uplift displacement of cone column foundation.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU445;TU473.1
本文编号：2430512
[Abstract]:According to the design principle of transmission line tower foundation in frozen soil area and the frozen soil characteristics of Wudaoliang area, two kinds of tower foundation, cone-column foundation and prefabricated pipe-pile foundation, are selected for field test. The experiment is divided into two parts: freezing period and thawing period, each period is divided into two working conditions: up-drawing and horizontal, down-pressure and horizontal. Based on the observation of displacement, internal force and lateral pressure of pile foundation, the QS curves and axial diagrams of different sections under graded loads are obtained. Through the research and analysis, it is found that the cone column foundation has good bearing capacity, reasonable selection and design of the foundation, and can be used as the line foundation of Qinghai-Tibet HVDC transmission line engineering. The section of pipe pile foundation is regular, the side wall is smooth, and the pull-out resistance is poor, so it can not be used as the transmission line foundation with higher uplift load. Through experiment and theoretical calculation, the formula of ultimate bearing capacity of pile foundation is derived, which is suitable to be used in permafrost area with large wind load. In order to use the finite element model to calculate the parameters of frozen soil, BP neural network is used to inverse the parameters, and the mechanical parameters of frozen soil of Mohr-Coulomb constitutive model are obtained. Based on this, a three-dimensional finite element model of cone-column foundation in permafrost is established, and the vertical and horizontal displacement cloud images of cone-column foundation in frozen soil are obtained. The accuracy and applicability of the model are verified by comparing with the conclusion of true test. According to the analysis of finite element model, it is found that when the depth of melted soil is 2m, the influence on the ultimate bearing capacity and vertical displacement of cone column foundation is small, but it has great influence on the ultimate bearing capacity and uplift displacement of cone column foundation.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU445;TU473.1
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