| According to the canal irrigation area of Ningxia frost damage problem, with the object of U-shaped concrete canal as the prototype canal in Ningxia. Arrangement related tests, observate shady and sunny slope canal base soil in different depths of the water, temperature and other indicators, based on the relevant experimental data.Arranging field frost heaving observation experiment in Ningxia university north campus. Application of automated data collection systems collect frost heave, frost force and temperature values, and based on field observations heave test data. Research on frost heave finite element model and numerical simulation of prefabricated concrete U-shaped canal. It provides the theoretical basis for the irrigation district water saving technological transformation. The results were as follows:(1) Field observation test heave from late-December to mid-January, canal soil frost heave is large. During the observation, sunny straight, sunny arc, shady straight, shady arc,the maximum amount of frost heave are 1.95mm,1.35mm,2.39mm,1.48mm,and on the same site observation, sunny slope frost heave first reach peak. One day, canal slope straight section bear both compressive stress and tensile stress, arc section mainly bear large tension stress; observation period, in sunny arc segment the maximum tensile stress is 14.2KPa, the maximum compressive stress is 0.3KPa; in sunny slope straight section the maximum tensile stress is 9KPa, the maximum compressive stress is 7KPa;in slope arc section the maximum tensile stress is 40.8KPa, the maximum compressive stress is 5.4KPa;in shady slope straight section the maximum tensile stress is 7.2KPa,the maximum pressure stress was 9.3KPa.(2) Through the numerical simulation of U-shaped concrete different structure of canal, with the increase of obliquity and thickness, uneven frost heave in reduced, frost heave displacement and the peak stress is also correspondingly reduced. Thickness of 10,8,6,4 cm at the same obliquity of the canal, the lining canal of circular arc section of frost heave displacement amplitude is small, almost does not change along with the change of thickness. When the obliquity is not greater than 8 degree, the increase of obliquity has greatly effect of uneven frost heave. When the obliquity is between 22 and 34 degree, the increase of obliquity has less effect uneven frost heave, and anti-frost effect was not significant. When the obliquity is between 8 and 22 degree, the increase of obliquity has moderately effect uneven frost heave. It is advisable to select 15-22 degree.(3) Through calculating thermal coupling of U-shaped concrete canal, U-shaped concrete canal thermal coupling calculation in non-permafrost, with increased soil depth temperature more close to a straight line parallel, almost unaffected by temperature boundary; simulation measured shady straight top section the convergence between shady straight and arc segment, canal bottom, the convergence between sunny straight and arc segment, sunny straight section the maximum normal sunny canal deep freeze were 25.5cm,19.8 cm,13.1 cm,12.2 cm,13.8 cm; shady slope frost heave greater than sunny the maximum shady canal base soil frost heave is 15.64mm,the maximum sunny frost heave is 7.0mm,arc segment frost heave relatively small(1.99mm-3.58mm);arc normal frost heave force is outer tension and internal compression the normal maximum frost heave force is 13.7MPa outside of the lining, and in inside of the lining the maximum frost heave force is 38.9MPa, the peak value both appeared in canal bottom. Arc tangential freezing stress is small, in canal bottom is 0, the peak appeared in the joint of straight slope segment and arc, the value is 19.3MPa. |
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