| Many drainage pipes in China were built before the 1980s.Due to the limitation of technology,most of these old drainage pipes adopt masonry arch culvert structure,and the section is usually large.Due to years of disrepair and other reasons,these old pipes may be damaged or even collapsed.In the trenchless repair of the pipe channel,in order to ensure the flow capacity of the channel after repair,the repair lining with excessive thickness is usually not designed,and the influence of the lining thickness on the crosssectional area of the channel is reduced as much as possible.For channels with less serious damage,semi-structural repair is usually considered.On the basis of considering the resistance of the original structure,the new and old structures are stressed together to reduce the thickness of the repair lining.Considering that the damage of masonry structure drainage arch culvert is mainly due to the deterioration of masonry mortar joint mortar,which reduces the integrity and bearing capacity of arch ring,and its block strength itself is sufficient.According to this characteristic,this paper puts forward the semi-structural repair of formwork construction method for structural reinforcement.The semi-structural repair adopted in this paper mainly achieves the purpose of reinforcement and repair from the following two aspects: a)The damaged masonry is reinforced by grouting to restore the mechanical performance of the original structure;b)The arch ring is constructed by formwork method to improve the bearing performance.The side wall is only reinforced by grouting,and the lining is not designed.In order to analyze the effect and feasibility of the technical theory,the following problems are mainly studied:(1)This paper analyzes the structural stress characteristics and failure causes of masonry drainage arch culvert,and studies the theory and factors to be considered of semi-structural reinforcement.Then the theory and design drawing of formwork semistructural reinforcement technology are given.(2)Through the compression test of damaged simulated masonry specimens and grouting repaired masonry specimens,the failure process and basic mechanical property parameters of masonry before and after grouting are compared.Finally,it is determined that grouting reinforcement can significantly improve the bearing capacity of damaged masonry,and it can be considered to further reduce the thickness of formwork repair lining in semi-structural repair design.(3)The finite element calculation model of arch culvert before and after semistructural repair is established by ABAQUS,the interaction between new and old structures under the semi-structural repair theory is simulated and analyzed,and the effects of dead load and three live load conditions on the internal force and deformation of arch culvert structure are compared.(4)Through the loading test combined with the actual project and the monitoring of structural displacement and strain of the original structure,it is found that the repair lining can well share the load on the arch ring of the original structure,which verifies the feasibility of the semi-structural repair technology of formwork method. |
