三次元均質等方弾性体の基本解とその応用 : 二種類の内部点加振解に基づく水平加振時の杭の動的性状に関する一考察-その6

Abstract

The purpose of this paper is to investigate the basic dynamic behavior of soil-pile interaction by an analytical method based on rigorous solutions. In this method, two kinds of complete solution of an elastic half-space and an elastic stratum overlying a rigid bedrock subjected to a harmonic point load in the interior are employed. These solutions, corresponding to generalized dynamic Mindlin' solution, have been derived from wave-propagation theory of a three-dimensional homogeneous isotropic elastic solid by the authors in previous papers. There have been few papers discussed the dynamic properties of soil-pile interaction based on three-dimensional wave-propagation theory compared with the numerous efforts on soil-foundation interaction problem. Therefore, this paper clarifies the characteristics of three different kinds of single soil-pile system subjected to a horizontally harmonic point load at the pile top in the following cases (a)〜(c). case (a) Floating pile in an elastic half-space. case (b) Floating pile in an elastic stratum overlying a rigid bedrock. case (c) Supporting pile in an elastic stratum overlying a rigid bedrock. Before studies on the nature of different soil-pile systems, the dynamic behaviors of soil subjected to a horizontally harmonic point load in the interior of a half-space and the stratum are discussed with a comparison of two solutions for the above elastic solids. These observations contribute much to understand the results of the response in soil-pile interaction. The analytical procedure to obtain the unknown displacement or traction on the soil-pile interface is similar to that of soil-foundation analysis using the solution in half-space subjected to a harmonic point load on the surface. The method in this paper is developed from the static pile studies of Poulos,^<6)> which contributed much to soil-pile interaction studies because the rigorous solution of three-dimensional elastic theory was used. The behavior of the three kinds of soil-pile system is investigated with parameter of pile flexibility factor K_R at the selected frequency. There is a considerable difference between the complex stiffness of the floating and supporting piles within the range of large K_R and the difference decreases with decreasing K_R. The different condition of soil-pile system has a greater effect on the imaginary part of the stiffness than on the real part. While the responses of a stiff pile are much influenced by the results of deep loading in the half-space and the stratum, the responses of a slender pile are strongly influenced by the corresponding shallow loading. It appears that there are slight differences between the two kinds of floating pile in the half-space and the stratum under this condition. Furthermore, the result of the pile responses shows the appropriate tendency, because the obtained relative relation of the stiffness between the floating and supporting piles is similar to Poulos' analysis.