| The effective utilization coefficient of farmland water use is an important indicator of water resources management and control,China Water Resources Bulletin 2021 indicates that the effective utilization coefficient of farmland irrigation water is 0.568,which has a comparative difference with the coefficient of 0.7 to 0.8 in developed countries.The frost heave destruction of big channels in seasonal freezing areas is one of the important factors that limit the increase of the effective utilization coefficient of farmland irrigation water in our country.Since the multi-point scattering and frequent situation of the lining hardness caused by the frost heave of the canal base earth that complementing and supplying the water caused by the higher underground water level,not only causes the waste of water resource,but also a waste of agricultural time,which will lead to the output quantity and quality of the grains.This problem urgently needs to be solved.For seeking of the frost heaving mechanism and mechanical properties of the base soil of the side slope of on irrigation channels with the high underground water level,this thesis takes the silty clay widely distributed in the irrigation area of Heilongjiang and with obvious frost heave as the research object,a soil scale reduction model of the side slope under the system of a two-dimensional open system that is equipped with complementing and supplying water function is established in this thesis,univariate experiments and orthogonal tests are carried out,and three-field coupled finite element analysis of frost heave hydrothermal power of canal side slope soil are conducted in this thesis,too.The following work are implemented:The single-factor test of frost heave of silty clay under the open two-dimensional system was carried out,and the average frost heave temperature,initial moisture content rate and the relationship between the additional pre-stressed force and frost heave force of slope side and slope top are achieved,depending on the relationship between the influencing factors and the test index,the factors and levels of orthogonal test were determined.Based on the single factor test,a three-factor-three-level orthogonal test with the influencing factors including the average frost heaving temperature,initial moisture content and pre-stressed force was carried out,the combination of maximum frost heave force and the influence sequence of factors in the slope top and slope side are obtained,and the significant influence of each factor on the test index was analyzed.Making use of the finite element software of COMSOL Multi physics and its PDE module,the second exploring modeling is carried out.based on the Fourier heat conduction equation of thermodynamic theory,the Richards equation of seepage theory in unsaturated soil,and the stress strain equation of frozen soil,a three-field coupled finite element model of frost heave hydrothermal power of the canal slope side soil is established,and through seeking for the results of the hydrothermal coupling differential equation of frost heave of the canal slope side soil,then compare the results with the experimental results,and finally the accuracy of the hydrothermal three-field coupled finite element model is verified.Applying COMSOL Multi physics finite element software,the finite element expansion test of canal fundamental soil is carried out,and the freeze-thaw cycle test under the most unfavorable combination conditions achieved in the orthogonal test is analyzed,and through the analysis of its temperature field,moisture field and stress field,it is known that the frost heave force produced during the freeze-melt cycle process can cause the deconstruction of the commonly used canal hardening.The research content of this thesis provides a base for the analysis of complex forces in the soil of the canal foundation under the open system. |
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