Experimental Study On Frost Prevention Of Canal Slope In Seasonally Frozen Area

The freezing and thawing in frozen area contributes to the continual change of the temperaturefield and moisture field beneath lining canal, which will seriously affect the safe operation of thechannel. Therefore, it is theoretically and practically significant to study frost heave mechanics andmeasures to prevent frost heave of canal. In this paper the analysis of the frost heave mechanics oflining canal was based on a combination of theoretical analysis, model test and numericalcalculation. Main contents were as follows:(1)Lining structure and base soil beneath were considered to be an integral part. Under a seriesof ideal conditions, the unsaturated soil hydrodynamic principle was applied to establishmoisture-heat-displacement coupling model, as well as determined the relevant parameters,boundary conditions and the numerical solution.(2)Modeled after the test engineering of “Beiyin-Wubeiduan” and taking the scale of fieldengineering, engineering geological and hydrometeorological conditions, as well as the practicalconditions of the laboratory into account, the similarity theory could be applied to determine thegeometric scale, time and temperature scale, and established an indoor model. To verify the thermalinsulation performance of insulation materials, comparative trials were designed, that were: slopeprotection structures of precast concrete board combining insulation measures and precast concreteboard only, and then controlled the environment temperature in the laboratory, and thereafterobserved temperature field, moisture field and displacement field of two slope structures, comparedand analyzed the results, after which, we could draw the insulating effect of insulation materials inthe revetment structure.(3)According to the size of indoor model and model parameters, used ABAQUS finite elementsoftware to simulate temperature field, moisture field and displacement field of two revetmentstructures under different environment temperature and then made a contrastive analysis withresults of laboratory test.Main conclusions were drawn as follows:(1)In terms of the test data, the freezing and thawing process of channels in frozen area was aprocess of one-way freezing and two-way melting. As a result of the temperature gradient, moisturemigration at different degree appeared. Moisture migration of surface was obvious under thecondition of a large temperature gradient and high-intensity heat exchange; and the closer to thechannel bottom, the smaller the amount of moisture migration was. Soil melting resulted ininfiltration of part of the migration water, which reduced the moisture. However, the final totalmoisture was still greater than the initial moisture. This was also the reason why the shear strength index weakened and the phenomenon of slumping occurred after freeze-thaw cycles.(2)Cold shrink phenomenon of channel slope always emerged first in the freezing and thawingprocess. With the temperature decreasing, frost heave appeared, and on the other hand, with thetemperature increasing, the ice in the soil melted into water, the volume reduced and then thawsettlement appeared. After a freezing and thawing cycle, the frost heaving amount was greater thanthe thaw settlement of channel slope, and residual deformation accumulated.(3)According to the test data, the frost heavy of revetment structure without insulation boardwas3.65times the depth of the revetment structure with it. It was thus clear that insulationmeasures could inhibit the development of the frost depth.Therefore, some appropriate insulationmeasures, such as covering insulation materials, setting insulation layer and so on, can be used inengineering construction in seasonal frozen areas.(4)The two-dimensional moisture-heat-displacement coupling model of saturated channel wasestablished on the basis of Harlan model. Appropriate simplifing was made in accordance with theactual engineering, and finite element software was used to perform simulation. The simulationresults were substantially consistent with the experimental results, which proved the correctness ofthe numerical simulation theory.The model test and numerical simulation theory in this paper provided a reference value forfrost prevention in frozen area.