Abstract
The presence of symmetric and asymmetric voids directly affects the mechanical behaviors of tunnel linings and further induces tunnel diseases among influence factors. In this paper, 1:5-scale model tests were carried out to study the mechanical behaviors of reinforced concrete (RC) linings considering the voids located at the crown and at the spandrel. Based on the experimental results and concrete plastic damage (CDP) model, the effects of void (i.e., location and size), subgrade stiffness, and lining size on bearing capacity of RC lining were investigated using numerical simulation. The results of model test and parametric analysis showed that the existence of voids significantly affected the mechanical behavior of the lining during inelastic deformation period. The lining with a larger void size corresponded to low bearing capacity and larger deformation around the void, thus increasing the damage possibility of linings. The influence of voids on the bearing capacity of linings varied with the void location, load direction (especially under horizontal symmetrical loads), and subgrade stiffness. High soil stiffness corresponded to a great influence of the void size on the lining bearing capacity. In addition, the lining strength increased inconsistently with the increase of model size. On the basis of parameter sensitivity analysis, the Levenberg–Marquardt (L-M) optimization algorithm and Logistic model were used to establish the equation of lining bearing capacity loss rate considering the void effect.
Highlights
With the rapid development of traffic construction in China, the number of operational tunnels is increasing rapidly
Concrete was modeled using the concrete plastic damage model (CDP model) in ABAQUS, which was proposed by Lee and Fenves and is suitable for simulating the mechanical behaviors of which was proposed by Lee and Fenves and is suitable for simulating the mechanical behaviors of concrete under monotonic and cyclic loading [28,29]
A comparison of the calculation results of the reinforced concrete (RC) lining with no void under mesh sizes of 5, 10, and 20 mm found that the load–displacement curves and peak loads under the three mesh sizes and 20 mm found that the load–displacement curves and peak loads under the three mesh sizes were were close, indicating that the simulation results of lining under different mesh sizes converged
Summary
With the rapid development of traffic construction in China, the number of operational tunnels is increasing rapidly. Most tunnels have defects such as voids behind the lining, insufficient lining thickness, low concrete strength, tunnel leakage, lining crack and corrosion, which can directly affect the safety and durability of the structures These have become problems that plague domestic and foreign traffic operation management departments, attracting widespread attention [4,5,6,7,8]. Defining the loss rate of the lining load carrying capacity and using the Levenberg–Marquardt optimization algorithm obtains the quantitative evaluation equation of the bearing capacity of the lining considering the effect of void This equation can provide a theoretical basis for the safety evaluation and strengthening design of defective lining
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