Study On The Impact Of Steel Corrosion On The Security And Durability In Tunnel Lining Structure

In the reinforced concrete structure, the volume of rust will become 2-4 times as much as its original one after the steel has been corroded. Therefore, the concrete around the rebar will be squeezed because of the expansion of the volume of the rust, and the extrusion pressure here is called expansive force. In the role of the expansive force, the expansive stress will be generated around the concrete. With the increase of the corrosion rate, the expansive force around the concrete will be increasing, eventually leading to tension cracking of the concrete cover. Once the concrete cover cracks, the corrosion of steel will be accelerated and the expansion of cracks will be further exacerbated, which eventually results in destruction of the structure and has a serious impact on its durability. Therefore, it is of great research importance to analyze the crack process of the concrete cover due to the corrosion.Taking the offshore tunnel Zhuhai Yanlangshan as the study background, by applying temperature expansion to steel during the process of numerical simulation, this paper intends to simulate steel corrosion and expansion, and to analyze the mechanical behavior of the reinforced concrete component and secondary tunnel lining under the effect of expansive force, with the main conclusions as follows:1. It can be concluded through the calculation that the tensile strength of concrete, the thickness of concrete cover and the diameter of steel all have an impact on the expansive stress of concrete cover and the corrosion rate of the steel when cracking. To be exact, the tensile strength of concrete and the thickness of the concrete cover are of direct proportion with the corrosion rate of the steel when cracking, while the diameter of steel is of reverse proportion with the corrosion rate.2. With the same corrosion rate, the expansive force is different in different parts of the lining. Accordingly, the expansive stress is of great difference, i.e. the expansive stress in the corner is at its maximum, followed by the vault and invert, the Waist and arch. Therefore, in the role of the expansive force, cracks will first appear at the corner of a tunnel, then in invert and vault.3. After the steel has been corroded, as the corrosion rate increases, the amount of the settlement is also increasing in the vault. However, corrosion of steel has little impact on sedimentation in the vault. During the process of corrosion rate increasing from 0% to 30%, the sedimentation increases by 1%, if only corrosion of steel is taken into consideration; while it increases by 1.4%, if both expansion and corrosion of steel are taken into account.4. When the corrosion rate varies between 1% and 30%, the internal force in the concrete lining changes differently. If only corrosion of steel is taken into consideration, the changes are not significant, which indicates that corrosion of steel has little effect on the internal force of the concrete lining; while if both expansion and corrosion of steel are taken into account, the internal force increases significantly, especially the tensile stress of the lining, and a lot of rust cracks appears, which demonstrates that the damage of lining structure caused by expansion of steel is enormous.