刚性摩擦桩回转振动分析及其在端承桩扭转振动中的推广

发布时间：2019-04-01 13:29

【摘要】：桩在动力荷载作用下的响应是桩基础研究的重要课题。动力荷载造成的上部结构的转动对于端承桩会导致扭转,而对于刚性摩擦桩则会导致回转。对于刚性摩擦桩的回转问题,可以根据基于混合物理论的非饱和土动力学模型而建立起问题的描述,从土体为多相介质以及发展弹性通解等角度进行研究,还可以将部分研究工作向扭转理论进行推广。基于复杂的理论分析,得到了以下成果:1)利用基于混合物理论的场方程,给出刚性摩擦桩在非饱和土中的回转振动的控制方程,同时将实心桩扩展到空心桩。对方程进行求解,根据所得到的解答对动力刚度等问题进行详细的分析。同时由于本问题的广泛性,给出了四种不同形式的退化:对于饱和土的退化、对于单相介质的退化、对于实心桩的退化和对于静力问题的退化。其中对于单相介质的退化有三种不同的方式。2)基于弹性通解理论,给出了含有体积力的广义轴对称平面弹性问题的通解。对于这一通解可建立两种不同的求解方式,并且将所得到的解答整理为积分型和级数型两种形式。关于解答的性质,证明了其解耦性、完备性和收敛性等。积分型解答较为通用,但级数型解答的收敛性较好,只要体力展开式的部分和有界(可以不收敛),应力解即收敛。甚至还构造出一个体力展开式部分和无界的情况下应力展开式收敛的特例。3)将本文所建立的广义轴对称平面弹性问题的通解应用于刚性摩擦桩的回转振动问题,并进行应力分析。根据分析的结果可知,当某一无量纲量(频率乘以半径再除以波速)值较大时,桩的半径不宜再视作直线。这一结果所对应的情况可以包括介质较软、频率较高以及半径较大等等。桩的扭转理论一定程度上也可参考这一点。此外,如果地震动有可能导致上部结构发生转动,则当计算竖向承载力时,应扣除所有可能发生回转运动并在运动中桩土交界面可能发生破坏的桩。4)将刚性摩擦桩的回转问题的部分研究成果推广至端承桩的扭转问题中,对扭转问题进行了应力分析,还在忽略桩周土的约束作用的条件下给出了扭转振动位移的简化算法。并且在求解过程中强调了方法的在原理上的严格性。
[Abstract]:The response of pile under dynamic load is an important subject in pile foundation research. The rotation of superstructure caused by dynamic load results in torsion for end-bearing pile and rotation for rigid friction pile. According to the dynamic model of unsaturated soil based on mixture theory, the problem of rotation of rigid friction pile can be described from the point of view of multi-phase soil mass and the development of elastic general solution, and so on, and the dynamic model of unsaturated soil based on mixture theory can be used to describe the problem. Some of the research work can be extended to torsion theory. Based on the complex theoretical analysis, the following results are obtained: 1) using the field equation based on the mixture theory, the governing equation of the rotary vibration of the rigid friction pile in unsaturated soil is given, and the solid pile is extended to the hollow pile at the same time. The equation is solved and the dynamic stiffness is analyzed in detail according to the obtained solution. At the same time, due to the generality of the problem, four different forms of degradation are given: for the degradation of saturated soil, for the degradation of single-phase medium, for the degradation of solid piles and for the degradation of static problems. There are three different ways for the degradation of single-phase media. 2) based on the elastic general solution theory, the general solution of the generalized axisymmetric plane elastic problem with volume forces is given. For this general solution, two different solutions can be established, and the solution can be classified into two forms: integral type and series type. On the properties of the solution, the decoupling, completeness and convergence of the solution are proved. The integral type solution is more general, but the series type solution converges better. As long as the partial sum of the physical expansion is bounded (which may not converge), the stress solution converges. Furthermore, a special case of the convergence of the stress expansion in the case of partial and unbounded physical expansion is constructed. 3) the general solution of the generalized axisymmetric plane elastic problem established in this paper is applied to the rotational vibration of rigid friction piles, and the general solution of the generalized axisymmetric plane elastic problem is applied to the rotational vibration of rigid friction piles. Stress analysis was carried out. According to the results of the analysis, when a dimensionless value (frequency multiplied by radius and divided by wave velocity) is larger, the radius of pile is no longer considered as a straight line. The corresponding conditions of this result may include softer medium, higher frequency and larger radius, etc. The torsion theory of pile can also refer to this point to some extent. In addition, if the ground motion is likely to cause the upper structure to rotate, then when the vertical bearing capacity is calculated, All piles that may be subject to rotational motion and possible destruction of the interface between the pile and soil in motion shall be deducted. 4) some of the results of the study on the rotation of rigid friction piles shall be extended to the torsional problems of end-bearing piles. The stress analysis of torsion problem is carried out, and the simplified algorithm of torsional vibration displacement is given under the condition of neglecting the constraint action of soil around the pile. In the process of solving, the strict principle of the method is emphasized.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TU473.1

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