Research On Analogous Mechanical Model Of Elastic Foundation Beam For Trapezoidal Canal Lining Frost Heave

Frost heave damage is the main way of canal lining damage in cold areas,which affects the safe operation of the canal and the utilization of engineering benefits.The establishment of a reasonable frost heave mechanical model of the canal lining is the basis of the canal lining anti-frost heave design.At present,the frost heave mechanics analysis of trapezoidal canal linings is mostly based on the structural mechanics analysis model established on the premise of assuming the distribution and magnitude of frost heave force and freezing force.Neither can it fully reflect the deformation coordination between the lining board and the frost heave of the foundation soil,nor can it make good use of the results or methods recommended by the code.SL23-2006 "Code for Design of Anti-Frost Heave of Canal System Engineering" recommends the calculation method of frost heave of canal foundation soil in detail,which comprehensively reflects the frost heave characteristics of canal foundation soil to a certain extent.Some on-site observations and prototype tests have also obtained free frost heave.Its size and distribution have important reference values for engineering design,but there are few mechanical models that fully absorb these existing results.Elastic foundation beam theory can well reflect the interaction between foundation and superstructure,but the interaction mechanism between frozen soil frost heave and lining is different from the general elastic foundation beam theory.Based on the theory of elastic foundation beams,it is necessary to establish an analogous mechanical model of frost-heave elastic foundation beams for trapezoidal canal linings based on the amount of free frost heave.In addition,the key issue of the application of elastic foundation beam theory in the analysis of frost heave of canal lining is whether the frost heave reaction coefficient can be reasonably determined according to the mechanical characteristics of the canal foundation soil after freezing and frost heave.There is no corresponding theory and method support.The main work and conclusions of this paper include the following aspects:(1)Based on the analysis of the mechanism of frost heave of canal lining and elastic foundation beam,the concept of frost heave reaction coefficient is put forward.The boundary conditions are established according to the coordination of force and deformation of the canal lining slab in the process of frost heave.Fully consider the results of the frost heave of the norms,tests and observation data.An analogous mechanical model of the frost-heave elastic foundation beam foundation of the trapezoidal canal lining is established based on the amount of free frost heave.Compare with previous experiments and numerical simulations to verify its rationality.(2)In order to explore the influence of nonuniform free frost heave of foundation soil caused by groundwater on frost heave of trapezoidal canal lining.The coordinated deformation between the nonuniform free frost heave of the foundation soil and the slope lining board is regarded as superposition of the nonuniform free frost heave displacement of the foundation soil,the rotation displacement of the lining board around the slope toe and the restrained displacement of the lining board.The calculation expressions for the amount of frost heave,frost heave reaction force,bending moment and shear force are given.The influence of different slope lining slab length on lining frost heave deformation and internal force and the difference between uniform free frost heave and uneven free frost heave on lining frost heave were respectively explored.(3)The frost heave reaction force coefficient is a very important parameter in the mechanical model established in this paper,which is related to the rationality of the calculation results.Based on the results of the frozen soil triaxial test,a Duncan-Chang constitutive model considering different confining pressures and temperatures was established.With reference to the method of determining the bed coefficient in the indoor triaxial test,the frost heave reaction force coefficient is obtained through numerical simulation.It provides strong support for the analogy mechanical model of the frost heave elastic foundation beam of the canal lining established in this paper.(4)Considering the nonlinear deformation of the canal base frozen soil and combining the research results of the frost heave reaction coefficient,an analogous mechanical numerical model of elastic foundation beam of the trapezoidal canal lining frost heave is established based on the nonlinear frost heave reaction force coefficient.Based on the finite difference method,the balance differential equation of the elastic foundation beam is discretized to adapt to the difficulty of solving the problem caused by the change of the reaction coefficient.Combining the three factors of the length of the lining slab,the nonuniform free frost heave of the foundation soil and the temperature,the influence of the nonlinear frost heave reaction coefficient on the frost heave of the trapezoidal canal lining is explored.