Research On Anti-frost-heave Experiment And Mechanics Model Of Small Concrete Lining U-shaped Canal

Ningxia is located in the seasonal frozen soil area,and the climate is cold.Due to frost heave,the lining structure of the channel has been damaged to varying degrees.Therefore,it is of great significance to carry out the prototype test of frost heave destruction of concrete lining channels in the seasonal frozen soil area.Taking the small U-shaped concrete lining channels in the Yellow Irrigation Area of Ningxia as the research object,a comparative test of the traditional plate seam structures of two-piece and multi-piece channels and the non-plate seam structure that eliminates the impact of plate seams was conducted in 2017-2018.By comparing the normal frozen expansion force and the size and distribution of the frozen expansion of the two structures,the relationship between the remaining frozen expansion of each part of the channel and the maximum frozen expansion force and the temperature and moisture content of the ground was analyzed.To investigate the influence of small U-shaped concrete lining plate seams on channel frost heave deformation in seasonal frozen soil area;On the basis of the analysis of the mechanism of channel frost heave,the damage characteristics of freeze heave and the factors affecting the tensile freezing strength,It is proposed that the normal freezing force of the traditional plate seam structure of the two collated channels is a load distributed triangular along the arc plate,and the canal top is zero,and the canal bottom reaches a maximum value.The formula for calculating the size of the tangential freezing force of any section of the channel is derived.Through reasonable simplification and hypothesis,a model of the frost failure mechanics of the two U-shaped concrete lining channels is established,which can not only calculate the interna!force of the are plate,but also the maximum bending moment,point,Moreover,the maximum normal freezing force and the maximum normal freezing force of the channel can be calculated.Finally,the rationality of the mechanical model is verified by an example and in situ monitoring data.The specific research results are as follows:(1)Small U-shaped concrete lining channels have a large shift in the frost-heave position at the plate seams,and the channels are also more prone to frost-heave damage.The observations on the test site found that the cracks in the lining plates are mainly caused by plate seams.(2)In the case of similar soil moisture content and temperature in channel lining structures,the two-piece and multi-piece U-shaped concrete lining structures that eliminate the impact of plate seams account for 100%and 73%of the frozen expansion forces in the complete freezing period respectively.Less than the traditional plate seam structure,In addition,the normal frozen expansion force distribution of the two types of channel after eliminating the influence of the plate seam is also more uniform.(3)In the case of similar soil water content and temperature in channel structure,the horizontal and longitudinal frozen heave positions of the two-piece U-shaped concrete lining channels are smaller than the traditional plate seam structures during the complete freezing period.The proportion of 63%and 60°/O of the plate seams and the longitudinal frostbite displacement of the multi-piece U-shaped concrete lining channels are smaller than the traditional plate seam structure,indicating that the more the plate seam,the less favorable the anti-frostbite deformation of the channel.(4)The frozen expansion displacement of small U-shaped concrete lining channel channel channel slope,slope foot and the bottom of the canal are positively correlated with the frozen expansion force and negatively correlated with the ground temperature and water content.The influence of ground temperature and water content on the frozen heave deformation of channel can be reduced.The anti-freeze heave deformation effect of various parts of the channel after the reinforcement of the two channels is:the bottom of the canal>the foot of the slope>the channel slope,After the reinforcement of the multiple channels,the anti-swelling deformation effect of each part of the channels is:the foot of the slope>the canal slope,but it is not conducive to the anti-swelling deformation of the canal bottom.(5)The normal freezing force of the traditional plate seam structure of the two-piece U-shaped concrete lining channel can be approximated as a load distributed triangular along the arc plate.At the top of the canal,the bottom of the canal reaches a maximum value,and the calculation formula of the shear freezing force of the arbitrary section of the two-piece channel is derived.On the basis of the above,a mechanical model of frozen heave failure of the traditional plate seam structure of the two-piece U-shaped concrete lining channel 1s established,and the comparison and experimental analysis with the known model shows that the mechanical model is more suitable for engineering practice and the calculation is simpler and more reasonable.