Spatial Rotations of Principal Stress Axes in Infrastructures on High-Speed Railway

The rotations of principal stress axes are special phenomenon induced by moving loads and deep excavations. It plays a significant role in the deformation calculation. The characteristics of the rotations of principal stress axes in semi-infinite foundation caused by a moving constant pressure are studied and the influences of surface wave on the characteristics are analyzed. The three dimensional elaborately numerical model for infrastructures including embankment, embankment-bridge transition zone and tunnel on high-speed railway are developed. The nonlinear factors such as material nonlinearity, generated geometry nonlinearity and contact nonlinearity are incorporated in the adopted models. The elastic recovery and radiation damping of infinite domain are reflected using three dimensional viscoelastic static-dynamic unified artificial boundaries. The dynamic behaviors of the infrastructures on high-speed railway under moving impulse pressures are investigated. The results indicate that the principal stress axes rotate in XY, XZ and YZ plane synchronously and continuously, the rotation in YZ plane predominate for embankment, embankment-bridge transition zone and tunnel. The rotations of principal stress axes at lower depth are greatly affected by surface waves generated by the interactions of P-wave and S-wave, the influence of surface wave on soil elements decreases with the increasing of depth. Stress concentrations occur near the transition zone due to the existing of large free surfaces. The rotation modes in infrastructures on high-speed railway are much more complicated than those in semi-infinite foundation. The rotations of principal stress axes can only be correctly obtained through wave motion analyses.