Durability And Bearing Capacity Evaluation Test Of Corroding Tunnel Lining In Offshore Areas

For various types of reinforced concrete structure engineering in modern society, corrosion of steel bar has been the most fundamental factor in affecting the safety and life span of structures. Therefore, in underground engineering tunnel lining structures, corrosion of steel bar is bound to affect durability of structures. Researches show that corrosion may lead to three important results,1) effective cross-section of steel bar is decreased, and so is the mechanical property;2) the adhesive property between steel bar and concrete is deteriorated;3) corrosion and expansion of steel bar will cause cracking of concrete. It is clear that these three elements are essential to the decreasing of structural durability.This thesis takes Yanlangshan Tunnel of Zhuhai Airport Expressway as research background, studying the influence of steel bar corrosion to tunnel structure. It is centered in laboratory tests in which "bending test" and "monopodium pull-out test" are adopted, combining with numerical simulation calculation, and some general rules are concluded about how reinforced concrete durability and bearing capacity is affected. Detailed research conclusions are as follows:1. After72sets of reinforced concrete samples are put under electric accelerated corrosion, steel bar electrochemistry corrosion mechanism is verified. By linear programming, corrosion degrees of the samples are tested. Corrosion degrees of the samples are compared by different concrete grades, protective layer thickness, and reinforced specifications. The affecting rules of every element are also concluded.2. After electric accelerated corrosion to72sets of bending samples and42sets of monopodium pull-out samples, respectively adopting eccentric compression and direct monopodium pull-out, the overall mechanical property of structures is tested, and the bending ultimate bearing capacity, deflection and concrete adhesive property are tested. Through series of data analysis, such as the relationship between structure deflection and compressed loading, strain value in different positions of strain foil under different load, pull-out cohesive strength, etc., conclusions are made about the rules that under different corrosion rates, how the bearing capacity is decreased, how concrete cracks and how adhesive property is deteriorated.3. On the basis of completed great indoor tests, by using of finite element numerical simulation software ANSYS, adopting cohesive force deterioration model, and combining with cohesive force degenerated curve obtained from tests, the tunnel secondary lining structure bearing capacity is simulated under different corrosion degrees, and how different corrosion degrees affect the relative slippage value of reinforced concrete inside lining structures is quantized. Under surrounding rock pressure, different corrosion rate lining structures’ bearing capacity change laws are obtained, and under strong corrosion the comparatively dangerous cross section of lining structure is also obtained.