Practical back-analysis methodology to predict underground train-induced building vibrations.

The vehicle-track interaction leads to the vibrating source for the prediction of train-induced building vibrations. To prevent modeling difficulties in the source part, this study proposes a practical back-analysis methodology for calculating underground train-induced building vibrations. The methodology combines the advantages of field measurements and numerical simulations. The fundamental concept of the hybrid methodology is to first create a virtualized moving source at the rail surface and subsequently modify it until the numerical predictions are consistent with the field measurements at the same locations. These locations are frequently selected at the ground surface or near the building foundation. Finally, this imaginary force can be used to predict the vibrations of buildings. The practicality of the hybrid methodology is verified by comparing the predicted vibrations of buildings with field test results. As an application of the proposed method, the transmission laws and characteristics of the vibrations in buildings are analyzed.

Stable response of axisymmetric two-phase water-saturated soil.

Biot's dynamic consolidation equations and Hankel transform were used to derive the integral solutions of stress and displacement for axisymmetric harmonic excitations in the two-phase saturated soil with subjacent rock-stratum. The influence of the coefficient of permeability and loading frequency on the soil displacement at the ground surface were studied. The results showed that higher loading frequency led to more dynamic characteristics; and that the effect of the soil permeability was more obvious at higher frequencies.

Dynamic properties of composite cemented clay.

In this work, the dynamic properties of composite cemented clay under a wide range of strains were studied considering the effect of different mixing ratio and the change of confining pressures through dynamic triaxial test. A simple and practical method to estimate the dynamic elastic modulus and damping ratio is proposed in this paper and a related empirical normalized formula is also presented. The results provide useful guidelines for preliminary estimation of cement requirements to improve the dynamic properties of clays.

Influence of water saturation on propagation of elastic waves in transversely isotropic nearly saturated soil.

Biot's two-phase theory for fluid-saturated porous media was applied in a study carried out to investigate the influence of water saturation on propagation of elastic wave in transversely isotropic nearly saturated soil. The characteristic equations for wave propagation were derived and solved analytically. The results showed that there are four waves: the first and second quasi-longitudinal waves (QP1 and QP2), the quasi-transverse wave (QSV) and the anti-plane transverse wave (SH). Numerical results are given to illustrate the influence of saturation on the velocity, dispersion and attenuation of the four body waves. Some typical numerical results are discussed and plotted. The results can be meaningful for soil dynamics and earthquake engineering.