Concrete Lining Canal Frost Heaving Numerical Simulation Based On Nonlinear Theory And Its Optimization

The amount of agricultural irrigation water accounts for approximately70%of the totalwater consumption in our country, and most of them are transported through canals. Previousresearches shows that seepage amount of canal transportation can be slumped to an greatextent on the condition that rigid lining is adopted as seepage control method compared withthose of earth canals, cutting60%~80%of the seepage, which undoubtedly rise the ratio ofwater utilization and meanwhile the efficiency of water transportation. However, in thenorthern irrigation areas of our country featuring cold and dry weather, unfrozen water in thebase soils of canal can migrates from unfrozen regions to freeze front under the force ofnegative temperature gradient, and result in the accumulation of water content and frostheaving of frozen soils. When this sort of frost heaving is restrained by both the concretelining board on it and unfrozen soil around it, an interaction is then therein established. Asespecially for the lining concrete, when the force is too large, concrete lining plates mayemerge with some cracks and fractures, if not well-controlled, this will lead to some moreserious damage problems, namely lining plate crack, bulge, collapse and landslides. That is tosay, frost heaving damages seriously weakened the seepage control ability of canal liningstructure, causing a large waste of water resources, and what worse is that these areas are theareas in our country where lacks of water severely. Furthermore, frost heaving damages notonly seriously affect the water transport efficiency and seepage control of canal, the damagedcanal lining structure as well requires a lot of labors and materials to be repaired, andsometimes even to need to be rebuilt. All in all, research on the mechanism of canal frostheaving damage is very meaningful, and can effectively reduce frost heaving damage liningstructure, and enjoys significant importance in saving water resources and agriculturalproduction. On the basis of mass literature reading, the main factors that influence the frostheave of canal base in permafrost regions and frost heaving damage of canal concrete liningstructure is concluded. On the basis of both material nonlinear theory and contact nonlineartheory, and using the finite element numerical simulation technology to simulate the frostheaving of canal base soil, an improved finite element model on this issue is established. Thenby adopting the method of parametric analysis, the effect of location and width of channel lining structure’s transverse expansion joints on reducing frost heaving damage is studied.The innovation points and the main content of this paper is as follows:(1) From the perspective of contact nonlinear and taking the simulation method of thecontact between concrete pile and frozen soil in permafrost regions as a reference, ansimulation method is used to simulate the interaction between concrete lining plate and frozensoil. In this simulation model the channel concrete lining plate and the frozen soil is taken astwo different parts, and the interface between these two parts is a contact element with whoseconstitutive model is in accordance with the constitutive model between the frozen soil andconcrete which can reflect the freezing contact behaviors of concrete and frozen soil. Resultsshow that the model which sets up an interface between concrete and frozen soil with contactnonlinear constitutive model can well reflect the frozen contact behavior between concretelining plate and frozen soil. Besides, this model can determine whether the concrete liningplate can be released from the frozen contact interface happens or not, thus truly reflectingsliding and failure criterion of the contact interface between the concrete lining board andfrozen soil. Compared with the model taking the concrete lining plate and frozen soil as onepart, the model’s simulation results of the normal frost heave force and tangential freezingforce are in more accordance with engineering practice.(2) Taking the possible large displacement of frost heaving in the process of frost heaveinto consideration, the lining concrete are likely to plastic yield, simulation using simplelinear elastic model cannot reflect the actual state of the lining plate’s stress and strain, thenan elastic-plastic constitutive model of concrete was used to simulate the stress distribution ofconcrete, the results of the numerical model with concrete using elasto-plastic model showthat canal lining concrete when in extreme frost heaving state will get into plastic stage, andthat is what a simple linear model cannot reflect. And the distribution of plastic strain alongthe lining plate can reflect the stress state and failure situation of the concrete lining plate,which is in well accordance with engineering practice.(3) From the perspective of material nonlinearity, on the basis of that the canal frostheaving numerical model with completely elastic constitutive model cannot reflect the realstress of lining concrete material and frozen soil in frost heaving situation, a numerical modelconsidering material nonlinearity of both concrete and frozen soil is built to study the canalfrost heaving. The results reveal that both frozen soil and concrete materials has entered thestage of plastic failure rather than stay at the elastic level in extreme frost heaving damagesituation, that is to say, the material nonlinear model can better reflect the reality of the stressstate when frost heaving happens.(4) After years of anti-frost heaving design of canal engineering practice and summarize, experts have advocate an rule of "allows certain frost heave displacement" and "avoidance"adaptive, reduce or eliminate the frost heaving in canal anti-frost heaving specification totutor the anti-frost heaving design of canal engineering. And it is widely admitted thatexpansion joint has a function of releasing deformation, so a parametric analysis is carried outon canal lining structure with expansion joint in different position and with different widthand their affecting in adapting to frost heaving, and the research results have a certainengineering significance.