Analysis Of Rotary Vibration Of Rigid Friction Pile And Its Extension In Analysis Of Torsion Vibration Of End-bearing Pile

The response of the pile under dynamic loads is an important subject in pile foundation research. The rotary movement of superstructure that the dynamic loads leaded to will cause the torsion of end-bearing pile and the rotation of the rigid friction pile. The description of the rigid friction pile’s rotation problem can be built established the unsaturated soil dynamics model based on the mixture theory, and researched from the points of view of seeing soil as multiphase medium and developing elastic general solution. Parts of the research can also be generalized to torsion theory. Based on the complex theoretical analysis, the following results have been got:1) Based on the field equations of mixture theory, the governing equation of rigid friction pile’s rotary vibration in unsaturated soil has been established, in which the solid pile has been extended to the tubular pile. A detailed analysis of dynamic stiffness and other issues can be established by the solution of the equation. Four different forms of degradation can be given because of the enormous of this problem: for saturated soil, for single-phase elastic medium, for solid pile and for the static problem. And for degradation of a single-phase elastic medium, three different ways have been established.2) The general solution of generalized axially symmetric plane elasticity problem containing the body force has been given based on the elasticity general solution theory. For this general solution, two different solving methods can be established, and there are two forms of solution: integral type and series type. Three theorems of decoupling, completeness and convergence have been proved. Integral solution is more general, but the convergence of series solution is good, and the stress solution will converge as long as the partial sum of the body force expansion is bounded(even maybe not converged). Even a special case can be constructed in which the body force expansion is bounded but the stress expansion is converged.3) The general solution of generalized axially symmetric plane elasticity which was established in this article can be applied to rigid friction pile’s rotary vibration problem to analyze the stress. According to the results, when a dimensionless quantity’s value(frequency, multiplied by radius, and divided by wave velocity) is large, the radius of the pile should not be regarded as a straight line. This situation can be occurred by the soft medium, or the high frequency, or the large radius. The torsion theory of pile can refer to it in a certain extent. In addition, those pile which the rotary vibration might happen to and the pile-soil surface might be damage should be deducted when the vertical bearing capacity be calculated if there is possibility that the seismic oscillation might cause the rotary of superstructure.4) Parts of the research results of the rigid friction pile’s rotary problem can be extended to the end bearing pile’s torsion problem and make the stress analysis. Also, a simplified algorithm of the displacement of the torsional vibration has been given in the conditions that the restraint of soil around pile can be ignored. The stringency of method in principle has been emphasized in the solution process.