| Ningxia is located in the upper part of Yellow River middle reaches, among which three-quarters of the land belong to arid zone, is a typical water-deficient areas. It is one of the prominent problems that water leak seriously to irrigating cannel from Ningxia Yellow River irrigation areas. In recent years, in order to ensure the national food security, the high standard fundamental farmland construction on high standard which demands irrigation district level bucket channels lining rate in100%and the lining rate of ditches in75%. However, having been faced with the problem of frost heaving damage to the lining structure for the need of anti-seepage from all channels and its severity will be revealed gradually.So based on the problem of the channel of the frost heaving damage in seasonal freezing zone, the new research progress in the canal seepage control and anti-frost heaving destruction was introduced at the home and abroad in recent years in this thesis. finally the detailed schemes of the small U-shaped channel concrete lining structure of frost heave deformation were puts forward, Taking the concrete lining structure of small U-shaped canal in the irrigation area of Ningxia as for example, choose Bayi branch ditch in Qianjin farm located in the north of Yinchuan as the study area, focusing on the Integral U-shaped, two arc-plates, three arc-plates of small u-shaped concrete lining structure in irrigation areas, conducted the antifreeze bulge test and observation from November2013to March2014, which was evaluated over a freeze-thaw season. This thesis sorted, analyzed, and discussed the figures and test results, and discussed the corresponding problems existing in the experimental observation.The test results are showed as follows:(1) Through theoretical analysis and experimental research, this paper reveals the frost heave mechanism and damage characteristics of typical experimental zone in the irrigation area of Ningxia (taking an example of Lateral canals and filed canals) small U-shaped channel.(2) Based on frost heave test, comparing figures of the temperature, ground temperature, frost line and frost heave deformation of three different U-shaped channel lining structure in frost heaving observation experiment, this paper reveals the laws between influence factors and the frost heaving damage degree, and analyzes the main failure time and parts as well as reasons of it, which shows:1) The ground temperature, three kinds of structure presented the trend of ground temperature increase with the increase of soil depth, and shadier’s temperature is lower that that of sunny side. For different testing points at the same time, in the same depth, ground temperature decreased from the bottom of the channel to the top ends of both sides, with canal bottom ground temperature highest. For sunny side, the upper hole’s ground temperature is generally higher than the under hole’s. It shows that because of the short sunshine duration, the temperature of under part of the ditch is lower than the upper’s ground temperature.2) Frost line, U-shaped canal of two arc-plates are east-west spell type, it shows that the frozen depth of northern slope is smaller than the southern slope’s. Northern slope is sunny side slope, the southern slope is clod side slope, froze depth of the bottom of drainage is greater than the sunny side slope and less than the clod side. U-shaped canal of three arc-plates is north-south channel, it shows that the frozen depth of western slope is greater than the eastern slop, in which the eastern slope is sunny side slope, and western is dark side slope. According to the surface damage of three kinds of lining structure after an observation of freezing and thawing cycle, the extent of damage of dark side slope is bigger than the sunny side.3) The amount of frost heaving, from the observation of distribution line of frost heave deformation of three arc-plates of lining channels, we concluded that the frost heave deformation of the bottoms of three channels are the largest. Second, for integral and three arc-plates lining channel, which belong to the north-south channel, we can see from the chart that sunny part’s frost heave amount is greater than the dark side slope’s. The two arc-plates lining channels, which belong to the east-west channel, has a great difference between the amount of frost heaving of the dark side slope’s and sunny side slope’s. Thus it can be concluded that the direction of the channel also is a decisive factor of the frost heaving damage.4) For monolithic channel concrete lining, the joint of segment and slope plate and bottom plate are the points which are easy to cause damaging, and the different lining all have small or larger frost heaving damage. For two spell type, the most dangerous point is the slope toe, after a freezing and thawing period of observation, some plates have tiny cracks. For the three arc-plates, we found that in1/3slope strengths there are longitudinal cracks throughout the channel, and appears in a large area.(3)Through the analysis and evaluation of various forms of lining of frost heaving and crack resistance, this paper compares the expansion effect of three kinds of antifreeze systematically, and finally combined with the engineering cost, construction factors, this paper puts forward the corresponding improvement measures and optimization scheme for the antifreeze bilge lining structure, which suited to the environmental characteristic of the channel in the irrigation area of Ningxia.Hoping the results can be helpful for further study of the perfecting frost heaving damage mechanism of channel lining, and provide the reference for further research of a complete set of irrigated areas of Ningxia irrigation area and the national natural fund project. |
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