Research On The Effect Of The Corroded Expansive Force Of Rebar On Reinforced Concrete Structure In Underground Structures

At present, with large-scale construction of underground structure, it is also stepping into a large-scale maintenance period at the same time in China. The durability of the underground structure has become an important subject to be solved, and the situation is going to grow in intensity in the near foreseeable future. For all kinds of reinforced concrete structure projects, damages caused by corrosion of steel bar has become the key factors affecting the structure safety and service life. A large number of facts and experiments show that there are three aspects of the reason for the reduce of the structure load-bearing capacity and safety due to the corrosion of steel bar:(1) the effective cross section of the steel bar is reduced, which leads to the decreasing of load-bearing capacity;(2) degradation of the bond property between steel bar and reinforced concrete;(3) volume expansion after the corrosion of steel bar, which is leading to the concrete crack. Since the environment that underground structure exits is very complex, corrosive damage rules of steel bars are more complicated.In order to research the attenuation law of the reinforced concrete overall mechanical properties in underground structures caused by steel corrosive effect, in this paper, the mechanical properties of corroded reinforced concrete experiment is designed, Combining with the underground structure design parameters, and using accelerated electrochemical corrosion testing methods. At the same time, it also studies the attenuation relationship of steel bar corrosion rate and the overall mechanical properties of reinforced concrete with the finite element numerical analog method. The main research contents and achievements are as follows:1. With single variable method, the influence rules of steel bar diameter, thickness of protective layer, concrete strength and corrosion time to the corrosive effect of reinforced concrete is researched, what’s more, change rules of concrete, mechanical properties of reinforced concrete and their bond properties is determined under the influence of the above factors.2. With ANSYS finite element numerical simulation software, the bond degradation model is built to simulate the changes of overall mechanical properties of reinforced concrete. On the basis of lab conclusions, the method of calculating the reduction rate of overall mechanical properties of reinforced concrete is given by corrosion rate.3. Taking shield tunnel of Shenzhen-Guangzhou passenger transport line as an example, the stress and displacement condition of segments with certain corrosion loss and under nine different corrosion states are are numerically calculated. In addition, and analysis of the security in the corresponding cases are carried out, which improve the method that evaluates the security of the underground structure by the corrosion loss.