Abstract
A 1/5-scale model test was used to analyze and compare the mechanical responses of engineered cementitious composite (ECC) lining and traditional concrete lining under vertically concentrated loading. Test results indicate that the major failure mode of the lining cross section is controlled by tensile stress. ECC linings express better cracking control capability and deformation performance than the traditional concrete tunnel linings. On this basis, the effects of loading direction, material tensile properties, soil stiffness, and model size on the mechanical behavior of ECC and R/ECC linings were analyzed by numerical calculation. Parametric analysis shows that the failure modes of ECC and R/ECC linings along different load directions are caused by the loss of bearing capacity due to the formation of three plastic hinges. Lining damage under horizontal loading is more concentrated than those under vertical and oblique loading. Improving the tensile properties of ECC materials can help enhance the load capacity and deformability of linings. Soil stiffness obviously affects the postpeak deformation behavior of ECC linings, as shown by the sharp increase of the load-displacement curve with the increase of soil stiffness. The peak load and corresponding displacement of linings demonstrate nonlinear increase with the increase in model size.
Highlights
A 1/5-scale model test was used to analyze and compare the mechanical responses of engineered cementitious composite (ECC) lining and traditional concrete lining under vertically concentrated loading
E failure modes of the ECC and reinforced ECC (R/ECC) linings were similar along different load directions (Figures 13 and 16), and they were characterised by the formation of three plastic hinges that led to the loss of load capacity of the lining structure. e R/ECC lining exhibited more distributed cracks than the ECC lining. is finding indicates that steel bars can help reduce stress concentration and subsequently lead to better crack control capability
When the peak tensile stress of ECC increased from 3.1 MPa to 3.6 MPa, the bearing capacities of the ECC and R/ECC linings increased by 5.9% and 2.1% and ductility increased by 13.0% and 10.8%, respectively. e ultimate bearing capacity and ductility factor of the R/ECC lining were higher than those of the ECC lining, which indicates that adding steel bars can improve the mechanical performance of ECC linings
Summary
The model of testing setup includes a reaction steel support frame, electrohydraulic loading jacks, and equivalent subgrade setup. E reaction frame was assembled by M30 bolts with nine H-shaped steel members in 3950 mm (width) × 2610 mm (height) × 300 mm (thickness) dimension. Compressive stiffness was 3.38 MN/m when compression deformation was lower than 20 mm, and it reached 4.87 MN/m when compression deformation exceeded 20 mm Both the results of the numerical simulation and prototype-loading tests showed that the deformation of the lining ring was lower than 20 mm. Erefore, prototype materials were used to construct the lining models in this test.
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