Slab Joint Response To Frost Heaving And Structure Optimization Of U-shaped Concrete Lining Channels

To explore the influence of concrete slab joints on frost heaving deformation in quarter frozen area,the different frost heave response of U-shaped concrete lining channel was taken as the research object through managing the monitoring test of integral,the two arc-plates and multiple arc-plates U-shaped lining channels which in Ningxia Yellow River irrigation area.Firstly,the cause of serious damage to the lining channels which are caused by the slab joints was analyzed through the monitoring data of frost heave in 2015-2016 freeze-thaw period.On this basis,An in-situ monitoring test was conducted on the conventional channel joint structure of the U-shaped concrete lining canal and the jointless structure that has been reinforced to eliminate the influence of the slab joints on the same channel during the freeze-thaw period of 2016-2017.Furthermore,the monitoring data of frost heave volume and frost heave force and the frost heave deformation of the slabs of two structures within a complete freeze-thaw were analyzed and dealt with.Based on the theory of Winkler elastic foundation supposition,a mechanical model of jointless U-shaped concrete lining canal with open system considering the normal and tangential direction of frozen deformation was established.The stress conditions under the forest surroundings were studied to obtain the normal frost heaving force,the tangential frost heaving force,and the formula for the internal force of concrete slabs.To monitor the jointless U-shaped concrete lining channels reinforced in the test area as an example.The frost heaving force and its internal force distribution were analyzed and calculated,and compared with the monitoring data and the existing mechanical model.Finally,the design concept of prefabricated U-shaped concrete lining channels connected by joggled structures is proposed.The research on the concepts,structural elements,force analysis,practicality,and impermeability was done through the above analysis.The specific research results are listed below:(1)The slab joint is the weakest part of the U-shaped concrete lining channel for frost heaving damage which is caused by the difference in frost heaving volume between the slabs on both sides of the slab joints.It was found that the frost heave damage of the slab joints is more serious than the slabs through the in-situ monitoring data analysis and most cracks start at the slab joints and extend to the lining slabs.(2)Under the similar conditions of soil temperature and soil water content,soil temperature,the frost heaving volume of the U-shaped concrete lining with jointless structure was less than that of the traditional U-shaped concrete lining structure.The former has a more uniform distribution of frost heaving force.(3)It is calculated that a large bending moment will occur at the bottom of the U-shaped channel and at the depth of 1/3 of the channel to the bottom by using the established mechanical model for considering the jointless U-shaped concrete lining channel under the double-directional frost heaving and open system.It shows U-shaped concrete lining with jointless structure has a good frost heaving performance.(4)The maximum bending moment happens to be the actual situation of the slab joints.A kind of joggled technique and its structural form with good stress conditions and anti-seepage performance are designed for the U-shaped concrete lining channel.