Stress release of the surrounding soil is the fundamental reason for many accidents in tunnel engineering. There have been a great number of numerical simulations and analytical solutions that study the tunneling-induced ground stress. This paper conducts a series of physical model tests to measure the stress state evolution of the surrounding soil during the tunnel advancing process. The ground compactness, as the most critical factor that determines the mechanical properties of sand, is the control variable in different groups of tests. The measurement results show that at the tunnel crown, the minor principal stress sigma 3, which is along the vertical direction, decreases to 0 kPa when the relative density (Dr) of the ground is 35% or 55%. Therefore, we can deduce that the sand above the crown collapses. When Dr = 80%, sigma 3 does not reach 0 kPa but its variation gradient is very fast. At the shoulder, the direction angles of three principal stresses are calculated to confirm the existence of the principal stress rotation during tunnel excavation. As the ground becomes denser, the degree of the principal stress rotation gradually decreases. According to the limited variation of the normal stress components and short stress paths at the springline, the loosened region is found to be concentrated near the excavation section, especially in dense ground. As a result, different measures should be taken to deal with the tunnel excavation problem in the ground with different compactness.

Proper consideration of variations in soil properties and their effects is necessary to enhance the seismic safety of structures. In this study, the effect of spatial variations in the cyclic resistance ratio on seismic ground behavior was investigated. Initially, dynamic centrifuge model tests were conducted on sandy ground featuring a 20% mixture of weak zones with low relative density and on homogeneous sandy ground with no mixture of weak zones. Subsequently, an effective stress analysis was performed by modeling the distribution of weak zones in the centrifuge model tests. Finally, after confirming the validity of the parameter settings, several analytical models with different weak-zone distributions were generated and numerically analyzed using random field theory. The results indicate that a local mixing of approximately 20% weak zones has only a limited effect on overall ground behavior. However, differences were observed in the rate of increase and dissipation of the excess pore water pressure ratio and in the residual horizontal displacement.