Nonlinear Parameters of Vibrating Foundations

A critical review of theories considering vibrating footings on the elastic half-space, and the comparison of their results with the simple damped oscillator show a principal insufficiency of a large group of theories frequently applied to the problem. The more exact theories yield nonlinear, i.e., frequency-dependent co-efficients for mass and damping of the system with a frequency-independent spring coefficient. Experimental results demonstrate the qualitative correctness of these results, but reveal quantitative deficiencies, and show an additional sublinearity of the spring coefficient, i.e., the shear modulus of soil, dependent on the amplitude of the dynamic stress-strain rate. The principal difference between the effects of dynamic and static load on soil is emphasized, and possible solutions for the nature of nonlinear elastic moduli of soil are discussed.