The Moisture-heat Coupling Effect Of Aqueduct In Natural Environment

Concrete aqueduct is a typical thin-walled water delivery structure.Under the natural environment,the change of external humidity and heat may cause tensile stress and cracks on the surface of aqueduct,which will bring great harm to the structure.Aiming at the moisture-heat coupling effect of aqueduct in natural environment,the main work and conclusions of this paper include the following aspects,:(1)The solution of humidity field and temperature field is the premise to study the effect of heat and humidity.The heat and humidity transfer process in concrete is coupled with each other.The nonlinear equations suitable for the study of the moisture heat transfer of concrete materials are introduced to determine the calculation parameters of the moisture heat coupling field;the concrete elastic constitutive equation considering the moisture heat effect is introduced to establish the numerical model of the moisture heat force coupling field of concrete combining with the boundary conditions and constraints.Considering the influence of environmental temperature,humidity,water temperature and sunshine on the surface of structure,the calculation method of aqueduct boundary condition in natural environment is determined.(2)Based on the engineering data of Kezi river aqueduct in Kashi area,a finite element model of rectangular aqueduct is established to simulate the effect of heat and humidity on the stress and deformation of aqueduct under the condition of full water delivery in summer.It is found that the deformation and stress of aqueduct considering the coupling effect of heat and humidity are greater than the simple superposition of temperature and humidity.Due to the influence of constant water temperature in the tank,the temperature change in the wetted range of the tank wall is very small,and the influence of temperature on the humidity diffusion can be ignored.With the increase of the infiltration depth of the groove wall,the side wall shrinks inward and the bottom plate deforms downward.Under the action of sunlight,the tensile stress inside the side wall increases and the tensile stress outside the bottom plate decreases,which is beneficial to the crack resistance outside the bottom plate and disadvantageous to the crack resistance inside the side wall.(3)In order to provide theoretical support for the design and maintenance of aqueduct and other thin-walled structures in the future,numerical experiments are carried out to simulate the variation of aqueduct heat and humidity effect in different seasons.Compared with the winter condition,the aqueduct is subjected to an initial temperature rise load in summer.In summer,the tensile stress on the outside of the bottom plate decreases,the tensile stress on the inside of the side wall increases,and the sunshine effect of the aqueduct is more significant in summer.Therefore,for the cold winter or sudden temperature drop climate,it is necessary to strengthen the floor insulation measures to prevent the external surface of the floor from cracking.(4)The finite element model of the aqueduct without tie rod is established under the condition of full tank in summer.Compared with the aqueduct with tie rods,the external tensile stress of the bottom plate of the aqueduct without tie rods is larger,the internal tensile stress of the side wall is smaller,and the effect of sunlight on the stress of the aqueduct is smaller.(5)No matter the temperature rise in summer or the temperature drop in winter,it has an adverse effect on the deformation and stress of the aqueduct with and without tie rods.Compared with the effect of temperature rise and temperature drop without temperature load,the effect on the aqueduct with tie rods is greater than that on the aqueduct without tie rods.It is necessary to set up heat preservation facilities for side walls and bottom plates of aqueducts in areas with large temperature difference.