Theoretical Evaluation of Guided Wave in Deep Foundations

摘要

A theoretical approach to non-destructive evaluation of deep foundations using guided waves has been formulated. Guided wave propagation is an infinitely long cylindrical pile embedded in soil is developed from dynamic equations of elasticity. Considering axisymmetric motion in the pile, the frequency equation of longitudinal modes is derived. The frequency equation represents a transcendental relationship between the non-dimensional frequency, and non-dimensional wave number. The solution to the frequency equation is satisfied by an infinite number of modes that form branches in non-dimensional frequency-non-dimensional wave number space. The first five branches of the longitudinal family of modes in a concrete pile embedded in soft/loose and hard/dense soils were numerically evaluated. Sensitivity analyses show that the real branches in the non-dimensional frequency-non-dimensional wave number plane are essentially independent of the shear modulus and density of the surrounding soil, and correspond closely to the branches of longitudinal modes in a free-standing pile.