Review and prospect of model test system for tunnel engineering structure

Abstract

In recent years, tunnel engineering is developing towards super-long and deep, multi-field and multi-phase coupling, thus, which easily induce the structural instability during tunnel construction and operation. Aiming at the mountain tunnel, underwater tunnel and urban tunnel, this paper expounds the research status of structural model test system, and points out the existing issues. The results show that: mountain tunnel model test takes into account passing through the adverse geological rock, and the loading conditions such as high ground stress, high karst hydraulic pressure and high seismic intensity. However, it’s hard to simulate the high stress of surrounding rock due to the size limitation of the apparatus. The model test of mountain tunnel is mainly based on plane strain model, which lacks the simulation of active fault with various dislocation forms under large-scale true three-dimensional stress condition. The model test of underwater tunnel has achieved stable high water pressure loading, but it is still unable to simulate the true three-dimensional underwater environment of the coupled stress field and seepage field. Additionally, the visibility of the chamber is poor, the seepage of the tunnel is only be characterized by the water inflow at the entrance, which makes it difficult to obtain the deformation law of the surrounding rock. Urban tunnel is affected by train dynamic load, pavement load and adjacent construction disturbance. At present, the model test usually considers the vibration response of the tunnel under a single load, and often ignores the structural characteristics such as segment joints and cracks. Thus, it is necessary to design novel and efficient local loading device to analyze the ultimate deformation characteristics of weak parts of segment to ensure the safety of subway operation. Finally, the bottleneck issues of tunnel engineering model test are summarized, and the internal visualization of the apparatus needs to be improved based on transparent similar materials. Aiming at the adverse geological conditions under high geostress conditions, a three-dimensional static-dynamic coupled model test system with expandable size is developed. Combining with the micro low-power wireless monitoring sensors and 3D visualization results display platform, a tunnel engineering structure model test system suitable for complex environment is established.