Study On Anti-frost Heave Of Prefabricated U-shaped Lining Canal Combined With Brittle-elastoplastic Materials In Cold Region

The distribution of water resources in China has obvious spatio-temporal characteristics,which are"more in the south and less in the north","more in summer and autumn and less in spring and winter".Therefore,the farmland in the north of China needs irrigation.In the agricultural irrigation water distribution system in China,two-piece precast U-shaped concrete lining channels are often used.Because of the smaller frost heaving force and uniform distribution,smaller frost heaving amount and stronger overall deformation performance,two-piece precast U-shaped concrete lining channels are widely used.However,the brittle characteristics of concrete materials are obvious,the ductility is poor,and the performance deteriorates after freezing-thawing cycle.In the process of frost heaving of canal foundation soil,the concrete lining channel is damaged under the action of frost heaving force,which leads to the waste of irrigation water and reduces the irrigation efficiency of agricultural water.In this paper,prefabricated brittle-elastic-plastic material combination of u-shaped lining channel,combine concrete respectively with glass fiber reinforced plastic and PE,establish concrete-FRP combination of u-shaped lining channel and concrete-PE combination of u-shaped lining channel,directed by lining channels from the frost heave load,using test and numerical simulation method of combining the analysis of different forms of combination of lining channel,Taking the relative usage amount of FRP and PE in the channel as variable,8 values of a is to=0.25,0.50,0.75,1.0,1.25,1.5,1.75,2.0 were taken to establish prefabricated lining channels with different usage amounts of FRP and PE.The influence of the change of the relative amount of FRP,PE and concrete on the failure characteristics,displacement and frost heaving resistance of lined channels was investigated,and the following conclusions were drawn:(1)When the relative amount of FRP in the concrete-FRP u-lined channel and the relative amount of PE in the concrete-PE u-lined channel a≤0.5,the concrete crack development is not completely sufficient after the failure of the lined channel,and the coordinated deformation of concrete,FRP and PE is poor;When a≥1,through cracks appear when the channel is damaged;(2)When the relative usage of FRP in the concrete-FRP u-lined channel is less than or equal to 1,its maximum displacement is less than that of the precast U-lined concrete channel;When a≥1.25,the maximum displacement of the lined channel is greater than that of the precast U-shaped concrete lined channel.With the increase of FRP thickness,the maximum displacement of lining channel decreases.With the increase of concrete strength,the maximum displacement of lining channel increases;(3)When the relative amount of PE in the concrete-PE combined U-shaped lining channel a≤0.5,the maximum displacement of the lining channel is less than the maximum displacement of the precast U-shaped concrete lining;When a≥0.75,the maximum displacement of the lined channel is greater than that of the precast U-shaped concrete lined channel;(4)When the amount of FRP used in the concrete-FRP u-lined channel is less than 1.25,the cracking load and failure load of the channel are lower than those of the precast U-lined channel;When a≥1.25,the cracking load and failure load of the lining channel increase with the thickness of FRP.With the increase of concrete strength,the ultimate cracking load and ultimate failure load of lining channel increase.When the PE relative usage of concrete-PE combined with U-shaped concrete lining channel a≤1.5,the anti-frost heaving capacity of the channel is lower than that of the precast U-shaped concrete lining channel.With the increase of concrete strength,both cracking load and failure load of lining channel increase;(5)Through the mechanical tensile test of FRP and PE after freezing-thawing cycle,the key parameters of mechanical properties after freezing-thawing cycle are introduced into the lining channel model for numerical simulation analysis and comparison,and the results show that:The maximum failure load of the concrete-FRP u-shaped lining channel and concrete-PE U-shaped lining channel decreases by 6.6%after freezing-thawing cycle,so the anti-frost heaving capacity of the lining channel decreases not significantly after freezing-thawing cycle;(6)The anti-frost heaving capacity and cost of different lined channels are different.The ratio of failure load to channel cost is used to measure the channel economy.If the ratio is large,the channel economy is good;otherwise,the channel economy is bad.Through comparative analysis,when the thickness of FRP is 5mm and the relative usage of FRP a is 2,the concrete-frp u-shaped lined channel is economical and has higher crack resistance.