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Segment reinforcement corrosion can cause bearing-capacity degradation of shield tunnel , which is unsafe for the metro operation. Therefore, a three-dimensional computational model was proposed in this paper to study the corrosion rate and rust expansion form of segment reinforcement by the combined action of soil loading, chloride ion and stray c...
Contexts in source publication
Context 1
... that the stray current may cause the segment steel bar corrosion, a four-layer resistance of the stray current distribution model, including the segment steer bar, was developed. Taking the train location as the boundary point, the power supply section is divided into two parts; the single-power model is shown in Figure 5. Sustainability 2021, 13, 3444 analysis the change rule of stray current, Ogunsola [30] set up a double-layer re model under single-train operation. ...
Context 2
... that the stray current may ca segment steel bar corrosion, a four-layer resistance of the stray current distr model, including the segment steer bar, was developed. Taking the train locatio boundary point, the power supply section is divided into two parts; the single model is shown in Figure 5. In Figure 5, RG, Rp, RG and RD are the longitudinal resistances of track, d network, structural steel bar and earth respectively, The h1, h2 and h3 are the tran conductance of track, drainage network, structural steel bar and earth, respectiv (x), UP (x) and UJ (x) are the voltages of the track, drainage network, structural s and earth, respectively. ...
Context 3
... the train locatio boundary point, the power supply section is divided into two parts; the single model is shown in Figure 5. In Figure 5, RG, Rp, RG and RD are the longitudinal resistances of track, d network, structural steel bar and earth respectively, The h1, h2 and h3 are the tran conductance of track, drainage network, structural steel bar and earth, respectiv (x), UP (x) and UJ (x) are the voltages of the track, drainage network, structural s and earth, respectively. IG (x), IP (x), IJ (x), ID (x) is the current of track, drain net, str reinforcement and earth, respectively. ...
Context 4
... simplification, Equations (1) and (2) can be expressed as In Figure 5, R G , R p , R G and R D are the longitudinal resistances of track, drainage network, structural steel bar and earth respectively, The h 1 , h 2 and h 3 are the transitional conductance of track, drainage network, structural steel bar and earth, respectively. U G (x), U P (x) and U J (x) are the voltages of the track, drainage network, structural steel bar and earth, respectively. ...
Citations
... Different calculation methods and model tests have been used to study the corrosion mechanism of rebars in underground structure [3][4][5][6][7]. Through several groups of model tests, Bertolini et al. [3] studied the corrosion rate of rebar in underground concrete under the action of a direct current (DC) and alternating current (AC). ...
... Based on real engineering examples and genetic programming, Gao et al. [6] proposed a calculation method for predicting the service life of tunnel structures subject to chloride-induced corrosion. Li et al. [7] established a corrosion calculation model of tunnel segment contained only a single row of main bars, research shows the 2D rust layer is distributed in an eccentric circle along the circumferential direction. ...
Track bed is the important support structure at the bottom of shield tunnel, during metro operation, the leakage of stray current will lead to corrosion of rebar in the track bed, which will affect the safe operation of metro. In this paper, the corrosion calculation model of track bed rebar under stray current is established, and the effects of stray current input mode and concrete resistivity on the corrosion rate of track bed rebar are studied. The result shows the corrosion rate of track bed rebar decreases nonlinearly with the increase of concrete resistivity, and the reduction gradient of corrosion rate in bilateral input mode is greater than that in unilateral input mode. With the decrease of concrete resistance, the corrosion area will cover the left half in unilateral input mode and cover both ends of track bed rebar in bilateral input mode. When the input point voltage increases by 40%, the corrosion current density in the middle of track bed will increase by about 61%.
... Considering that SWSSC contains a lot of chloride ions, shells, and other impurities [23,24], it is necessary to use rust prevention technology when combined with steel bars [25] or controls the content of chloride ions in concrete within a specific range. Otherwise, the structure's service life will be seriously affected [26][27][28][29]. However, the steel bar rust inhibitor and reducing chloride ion content cannot solve the durability problem of concrete structures in marine engineering. ...
The wide implementation of fiber reinforced polymer (FRP) in seawater sea-sand concrete (SWSSC) structures can help solve the durability problem of infrastructure in marine environments and reduce the excessive use of fresh water resources and river sand in construction. Besides, it is conducive to reducing carbon emissions and realizing the grand goal of greener construction. This paper comprehensively summarizes the degradation law of the mechanical properties of carbon (C), glass (G), and basalt (B) FRP bars in seawater (SW) and seawater sea-sand concrete (SWSSC) environments and the bond strength and overall bearing performance of FRP-SWSSC structure. The main factors causing the degradation of the mechanical properties of FRP bars are the erosion of the internal alkaline environment and the external seawater environment of SWSSC. The microscopic test revealed the microscopic degradation mechanism of FRP bars in the SWSSC environment. It is mainly manifested in the increased moisture absorption of FRP bars after exposure to the SWSSC environment, the emergence of new chemical functional groups in the infrared spectrum, and the digestion of resin matrix and corrosion of fiber in the SEM scanning image. In addition to a comprehensive summary and evaluation of the current research results, this study also analyzes the shortcomings of the current FRP-SWSSC research stage and puts forward some valuable suggestions for the future research direction of the FRP-SWSSC structure.
... Ordinary rebars are prone to corrosion and expansion. Therefore, concrete structures can be damaged, and building life is severely reduced when the volume increases beyond the elastic limit of concrete [5][6][7]. In addition, roads must be maintained, which has high costs. ...
The existing process for the preparation of cladded rebars is too complicated for large-scale industrial production. Therefore, this paper proposes a 55#/316L rebar preparation method based on vacuum hot rolling. The microstructure and mechanical properties of the composite interface of the rebar, along with the connecting technique, were studied using transmission electron microscopy, X-ray diffraction, and Vickers hardness testing. The obtained results showed that the minimum thickness of the 55#/316L rebar cladding was 0.25 mm, which was twice that of the M 329M/M 329-11 design standard used in the United States of America. Due to the diffusion of carbon, large numbers of second-phase particles were precipitated on the stainless-steel side, which resulted in intergranular chromium depletion. After multi-pass hot rolling, the minimum bonding strength of the composite interface reached 316.58 MPa, which was considerably higher than the specified value of 210 MPa. In addition, we designed three different types of rebar connection joints: sleeve, groove-welded, and bar-welded. According to the tensile test, the bar-welded joint had higher yield strength (385 MPa) and tensile strength (665 MPa) than the base rebar (376.6 MPa and 655 MPa), as well as a very high corrosion resistance.
... Different calculation methods and model tests have been used to study the corrosion mechanism of rebars in tunnel structure. [11][12][13][14][15] Through several groups of model tests, Bertolini et al. 11 studied the corrosion rate of rebar in underground concrete under the action of a direct current (DC) and alternating current (AC). Dolara et al. 12 developed a numerical model for a simplified shield tunnel and determined the corrosion area of rebars exposed to stray current. ...
... Based on real engineering examples and genetic programming, Gao et al. 14 proposed a calculation method for predicting the service life of tunnel structures subject to chloride-induced corrosion. Li et al. 15 established a corrosion calculation model of tunnel segment contained only a single row of main bars, research shows the 2D rust layer is distributed in an eccentric circle along the circumferential direction. ...
During subway operation, cracks may appear at the arch waist of tunnel segment surface. Under the acceleration of stray current, chloride ion in groundwater will penetrate into the surface of rebar through cracks, resulting in segment rebar corrosion and structural stiffness degradation. In this article, the rebar corrosion calculation model of tunnel segment contained transverse crack under stray current and chloride ion was established, and the coupling of electric field and chemical field in cracked concrete was realized. The effects of chloride ion content and input voltage on the rust layer distribution of cracked segment were studied. The results shows: Under the action of stray current and chloride ion, the 3D rust layer of cracked segments at the arch waist can be described by Gaussian mixture function. In the longitudinal direction, the rust layer at the crack section is located at the peak of the rust layer curve, and the increase of chloride ion content has a greater influence on the rust layer shape than the increase of stray current. When the chloride ion content and stray current are doubled, respectively, the maximum rust layer thickness of rebar will increases by 34% and 16%, respectively. In the circumferential direction, the nonuniform coefficient of elliptical rust layer will change with the increase of segment crack width and chloride ion content, but it will not be affected by stray current intensity.
