Research On Frost-heaving Effect Of Concrete Lining Of U-shaped Canal Considering Double-directional Deformation

With the rapid development of society and economy,the shortage of water resources in Northwest China is becoming more and more prominent.Ningxia Yellow River Irrigation Area,as one of the famous large-scale irrigation areas in China,has a large number of irrigation projects.Among them,the anti-seepage canal lining with concrete slab will suffer serious frost-heaving damage under the action of negative temperature in winter,resulting in canal leakage and waste of irrigation water resources,which restricts the construction of high-standard farmland and the high-quality development of modern irrigation agriculture in Ningxia Yellow River diversion irrigation area.Therefore,it is of great theoretical significance and engineering application prospect to explore the structure form and frost heave effect of concrete lining seepage prevention canal.In this thesis,on the basis of consulting relevant literature and summarizing the existing research results of frozen soil and canal frost heave resistance,by the prototype monitoring test,theoretical analysis,the mechanical model and finite element numerical simulation,in view of the situation that concrete lining slabs with dense joints are not conducive to resisting frost-heaving deformation in engineering practice,from the perspective of considering both lateral and longitudinal deformation of the canal,the frost-heaving effect of U-shaped concrete-lined canal with large span has been studied.The specific research contents and results are as follows:(1)On the basis of the prototype observation about the temperature,water content,earth pressure and frost-heaving data of two-piece and multi-piece U-shaped concrete lining canals have been analyzed and processed,and the temperature gradient of the canal foundation soil has been analyzed by using AKIMA interpolation method.The characteristics of frost-heaving effect of U-shaped concrete lining channels after reinforcement have been analyzed.It is concluded that the anti-frost-heaving performance of U-shaped concrete lining canals can be improved by slab-joint reinforcement measures.(2)The whole large-span U-shaped canal is regarded as a beam placed on elastic foundation,and the mechanical models of the canal slope and bottom have been established based on the theory and Winkler hypothesis.Compared with the prototype observation results of the whole large-span U-shaped canal and the existing research results,the rationality of the mechanical model has been verified.(3)The software ANSYS has been used to simulate the frost-heaving effects of canal temperature field,displacement field and stress field considering only transverse deformation and bidirectional deformation respectively.It has been found that the simulated results are in good agreement with the measured values,and the obtained rules are basically consistent.The frost-heaving of the whole large-span U-shaped canal considering the bidirectional deformation is less than that of the small-span U-shaped canal considering only the transverse deformation.(4)Through the method of single factor variables,according to different longitudinal span,openings,angle and lining thickness,the whole U-shaped canal structure has been simulated by using the numerical mode and the effect of these factors on canal frost-heaving have been analyzed.And the design of the large span U-shaped canal has been optimized by connecting with the actual situation of Ningxia Yellow River Irrigation Area.