Large-scale Shaking Table Model Research Articles

Large scale shaking table model test and analysis on seismic response of utility tunnel in non-homogeneous soil

Underground utility tunnels are the most fundamental and reliable lifeline network in urban cities, and are widely constructed throughout the world. In urban areas, most utility tunnels usually encounter the non-homogeneity of subsoil condition due to various construction effects. Studies have shown that the damage mechanism of shallow underground structures mainly depends on the inhomogeneity of the subsoil conditions. This would become a considerable factor for the stability of the underground utility tunnel structures. However, this type of research still needs to establish the vulnerable seismic design. In this study, a series of shaking table tests were conducted on non-homogenous soils to investigate the performance of seismic interaction between utility tunnels, surrounding soils and interior pipelines. The dynamic responses measured from the test account for the boundary condition of non-homogeneous soils, the internal forces, displacement of tunnel joints, the dynamic characteristics on interior pipelines and the reasonable spring stiffness with damping in the seismically isolated gas pipeline model inside the tunnel. The vulnerability of underground utility tunnel in non-homogeneous soil zone and the mechanism of the stability of interior facilities are the main topics discussed in this paper.

Study on Dynamic Response of Pressure Type Anchor and Lattice Beam System Under Seismic Loadings

In order to investigate dynamic response of anchoring landslide under seismic loadings with different loading magnitudes, a large scale shaking table model test was carried out, and the acceleration response of anchoring landslide, mechanical characteristics of anchors and lattice beams were studied respectively. The test results indicate that (1) under lower loading magnitude 0.05–0.2 g, the PGA amplification factors of different soil layers in landslide, and the dynamic response in different layers of anchors and lattice beams all have little differences. (2) Under 0.2–0.4 g, the PGA amplification factors of different soil layers and the anchoring force of different layers of anchors continue to increase. The strain of the top anchors and the bending strains of the top crossbeams are slightly greater than that in other layers. (3) Under high loading magnitude 0.4–0.6 g, the strain of the upper anchors continues to increase and it is much greater than that in other layers, and the bending strain of the top crossbeam increases sharply and generates obvious tension-bend deformation.

Dynamic Responses of Bridge–Tunnel Overlapping Structure for High-Speed Railway Under Different Seismic Excitations

There are many bridges and tunnels been built overlapping or close to each other during railway constructions in west or south China recent years. For bridge–tunnel overlapping structures on high-speed railway, serious damage or even complete destruction could be caused when powerful earthquake occurred in complex topography or poor geological areas. However, there is still little research yet on this kind of complex system taking interactions of bridge–tunnel–rock into account, especially for seismic damage or dynamic response mechanism. For purposes of dynamic response analysis and reasonable anti-seismic measures for complex bridge–tunnel overlapping structures, large scale shaking table model tests have been carried out. In shaking table model test, EL-Centro wave (EL) and the Wenchuan wave (WC) were adopted as loading wave in X, Y, Z-direction (perpendicular to the tunnel axis, horizontal along the tunnel axis, and vertical). Test results demonstrated significant differences existing on dynamic responses or variation laws especially in different seismic excitation cases, and fateful consequences could be caused. It also indicated that several sensitive and fragile parts (e.g., the arch vault and arch foot at enlarged section of the tunnel, at the end of the beam and the top of the abutment inside the tunnel portal, and the soil above the tunnel roof etc.) should be strengthened or required special treatment for structural security or overall stability. Simultaneously, seismic excitation combination analysis is important for such overlapping structures in weak surrounding rocks or soils. And the influence caused by the tunnel longitudinal direction should not be ignored for seismic response analysis for such structures. Bidirectional or multi-directional seismic excitation method is proposed for the rationality and accuracy on seismic tests or anti-seismic analysis for same or similar structures.