Experimentation Research Of The Frost Heave Deformation On Channel With Small U-shaped Concrete Lining

The contradiction between supply and demand that shortage of water resources, inconsequence of water distribution and waste of water project has caused more acute embarrassment and seriously restricted to our social and economic sustainable development in Ningxia. In order to achieve the goal the coefficient of effective utilization at irrigation water reaching 0.5 above which a saving water index during the "12th five-year Plan", the high standard farmland construction including to inhance the anti-seepage lining rate for irrigation canal has been expanding rapidly.According to the on-site investigation information, the concrete structure of anti-seepage lined was taken in most channels system of Ningxia irrigation area. The small U-shaped concrete lining structure has been widespread applied in lateral canals, where the main types of lining structure consist of monolithic U-shaped, two arc-plate U-shaped and multiple arc-plate U-shaped, etc. Since Ningxia is located in the seasonal frozen, the frost heaving damage phenomenon is very serious problem to lining structure of canal. But the large number of research fundings with the frost heave problems on canal lining structure mainly focused on main canals of large and medium-sized now. There is not suitable for small cross-sectional dimension and periodic water of canal such as U-shaped lateral canal. Through the field in situ observation and theoretical analysis, the deformation and failure characteristics of freezing and thawing for small U-shaped canal lined by concrete structure was discussed. Finally, a design method of the aqueduct type field ditch with pre-installed was put forward based on the monitor data and investigation results.The main conclusions in this thesis are as follows:(1) The whole anti-frozen heave of concrete lined structure with small U-shaped canal is higher. And the cross-sectional dimension of U-shaped canal is smaller, the joint with lined structure is less, the deformation of frozen heave is smaller, the displacement of frozen heave distributed more uniformity and continuation. The frozen heave displacement of lined structure on sunny slope is greater than shady slope, and the deflected tendency to shady slope is obvious. Meanwhile, the frozen heave displacement of lined structure with rigid joints and the position of staggered joints is a close correlation.(2) During the freezing and thawing period, the soil moisture of canal bed has obviously redistributed characteristics. After melting of soil moisture content with canal bed is less than before the freezing.(3) There is no significant correlation between geothermal and duration of freezing-thawing period. The short-term cataclysm of geothermal is little impact on frozen depth. Meanwhile, the frozen depth much affected by accumulated of extreme negative temperature.(4) During the freezing and thawing period, the values of ground temperature below concrete plate was connected to air temperature changes, monitoring depth and observation time. Below 30cm depth of plate, geothermal values are greatly influenced by the accumulation of extreme negative accumulated temperature. The relationship between geothermal and extreme negative accumulated temperature affected by monitored depth. And there existed a quadratic function relationship between geothermal and duration of freezing-thawing period. In this depth range, the geothermal observation values of sunny slope is lower than shady slope when in the 9:00am, but sunny slope geothermal is higher than shady slope while at 2:00pm. Under 30cm depth range of plate, there is no significant correlation between geothermal and average of extreme temperature. On the basis of geothermal change characters, where exist a quasi constant temperature layer around 30cm depth under plate. Meanwhile, the geothermal values affected by canal bed soil moisture content and canal section size significantly.(5) The frozen heave damage included the transverse displacement and the longitudinal deformation. The integrity of antifreeze ability is stronger when the lined structure joint is less. There is significantly linear correlation between the frozen heave displacement of lined structure and multiple causes of frost heave which main included accumulated of extreme negative temperature, geothermal and frozen depth of canal bed soil.(6) As a new design method at the end of the canal system, the aqueduct type field ditch with pre-installed presented in this thesis is rationality and can meet the requirements of economic technology of local engineering construction.