Research On Integral U-Shaped Concrete Canal Lining-Frozen Soil Contact Model Based On ABAQUS

In the cold regions of northern China,there was a large amount of frozen soil,and its uneven frost heave displacement causeed damage to the canal lining structure,which seriously affected the canal impermeability and water transfer efficiency.Frost heave damage of canal lining was directly related to the lining-frozen soil contact action,and the contact relations such as freezing constraint,frictional slip and separation between its contact surfaces directly affected the lining force and structural stability.Current lining-frozen soil contact simulations were mostly steady-state analyses and lacked experimental verification in the mechanical part.This study was based on the monitoring experiment of frost heaving damage of integral Ushaped canal in the river-loop irrigation area,and the lining-frozen soil contact separation and relative sliding process in the experiment were verified and analyzed by monitoring indexes such as subsoil temperature,frost heave displacement of stratified subsoil layer,canal lining frost heave displacement and soil stress around the canal;the mechanical model of integral Ushaped canal frost heave damage was established with the experiment canal as the prototype,and a finite element model of frost heave damage of integral U-shaped canal was constructed in ABAQUS.The thermal coupled finite element model considering contact and no contact were constructed and numerically simulated in ABAQUS,and the reasonableness of the model was evaluated by combining the experiment results;integrated the experiment and consider contact simulation,analyzed the dynamic processes of canal lining-frozen soil contact,investigated the effect of contact relationship on contact stress with canal obliquity as the variable,and proposed reasonable engineering suggestions.The following research conclusions were mainly obtained:(1)Canal lining frost heave displacement and soil stress around the canal were directly related to the temperature field and frost deformation of the subsoil.The temperature field of the subsoil showed a U-shaped diffusion pattern with the canal lining as the center and the surrounding subsoil affected by its temperature change.The local water level was high,and the precipitated ice layer of the middle and lower subsoil had sufficient water replenishments in the process of frost heaving process,which directly affected the frost heave displacement of the subsoil and leaded to stress and frost heave displacement of the lining by extrusion.(2)There was a separation and relative sliding process between the canal lining and the frozen soil contact surface in the live experiment.In the three-years experiment,the soil at the bottom of the canal had no soil stress for a long time,and the amount of subsoil frost heave displacement and lining frost heave displacement were not synchronized,so it was presumed that the lining at the bottom of the canal was separated from the subsoil to produce voids.In the first two years of experiment,the lining was not completely displaced upward with the frozen subsoil,and the lining frost heave displacement and soil pressure at the slope of the canal had extreme misalignment,so it was presumed that the relative sliding between the contact surface of the lining and the subsoil at the slope of the canal occured,and the process released the contact pressure.In the final year of experiment,the lining as a whole had been deflected and the lining was under maximum subsoil pressure at the shady slope.(3)Considering contact action in the canal frost heave model changed the development trend of foundation soil stress,reduced the simulated error of soil pressure and stress peak,and made the simulation results more consistent with the live experiment.The difference between the temperature field,subsoil frost heave displacement and lining frost heave displacement simulated by the experiment and the two types of models was small.At the canal slope,the simulated stress peak of the model without considering contact could be up to 3.3times of the peak of the simulation with considering contact and the experiment monitoring.The stress at the bottom of the canal was basically zero in the experiment and considering contact simulations,while there was a continuously increasing tensile stress in the simulation without considering contact.After considering contact,the peak positive stresses on the upper and lower surfaces of the lining were reduced by 903% and 164%,respectively,and the peak tangential force on the lower surface was reduced by 248%.(4)The separation of the canal bottom between the lining-frozen soil contact surface and the relative sliding process of the canal slope directly influenced the contact stress.After the subsoil started to freeze,the lining at the bottom of the canal separated from the subsoil,after which the tangential stress at the contact surface reached the freezing strength and the sliding of the canal slope lining occured,and the lining was still displaced upward while the confining stress was released.The maximum of contact normal stress appeared at the shady slope,and the maximum of tangential stress appeared at the shady slope first and then the sunny slope;under the action of shear stress,the lining appeared to deflect to the shady slope first and then to the sunny slope.(5)The canal obliquity angles changed the lining-frozen soil contact relationship and affected the stress distribution at the contact surface.Simulations of the frost heave damage process were carried out for canal obliquity angles of 0°,10° and 20° based on the considering contact model.The simulated contact normal stress maximums at different obliquity angles were all distributed at the connection between the circular arc section at the bottom of the canal and the straight plate of the side slope,and the contact normal stress and tangential stress at the shady slope reached the maximum around the 30 th day of simulation.In view of the location of the contact stress maximums and lining damage characteristics,comprehensive canal footprint,project benefit and structural resistance to frost heave performance to select the appropriate angles of obliquity,which could achieve the effect of reducing the subsoil frost heave extrusion damage.