Chengshi guidao jiaotong yanjiu (Aug 2024)
Deformation and Crack Propagation Characteristics of Carbon Fiber Reinforced Concrete Shield Segments Based on Particle Discrete Element
Abstract
Objective The Xiaozhuang Station-Wanshou Station interval shield tunnel is located in a highly fractured rock layer with developed groundwater, facing extremely complex geological conditions and requiring relatively high crack resistance and compressive strength for prefabricated segments. However, ordinary concrete segments cannot meet structural crack resistance requirements. It is suggested to incorporate carbon fibers into the concrete and carry out in-depth study on the deformation and crack propagation characteristics of carbon fiber reinforced concrete shield segments. Method Based on particle discrete element theory, the microscopic strength parameters of the concrete material parallel bond contact model are determined through the stress-strain curve of a uniaxial DEM (discrete element method) test. A numerical model for the bending strength test of carbon fiber reinforced concrete segments is established to analyze the strength, failure characteristics, crack propagation mode, and deformation of the above segments. Result & Conclusion Numerical simulation results of the bending strength test show that under different loading conditions, the improvement effect of carbon fibers to concrete segment strength is limited. However, the carbon fiber structure has significant tensile strength, which notably enhances the deformation and fracture resistance of the segments. During the loading process, the carbon fiber reinforced concrete segments initially develop a vertical tensile crack at the bottom. As the loading continues, three vertical tensile cracks are generated at the bottom without crushing collapse phenomenon occurring yet, but when the loading reaches the ultimate compressive stress of the concrete, compressive cracks appear in segments. As the compressive cracks penetrate the tensile cracks, the segments will reach the ultimate strength failure state. Throughout the loading process, there exists a region with minimal deformation within the carbon fiber reinforced concrete segment. As the loading continues, this region gradually shifts from segment joint end to loading head position. It is observed that carbon fiber reinforced concrete segments can meet the safety and stability requirements of interval tunnels in fractured rock layer with developed groundwater.
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