Experiment Research Of Frost Heave On U-shaped Canal With Concrete Linging And Discussion Of Frost Heaving Mechanics Model

Water shortage is the biggest constraints to agricultural development of Ningxia in the 21st century. With the accelerating of reform and development of irrigation and water, the increasingly prominent contradiction of water resources is more seriously in Ningxia, especially the high agricultural water demand. In response to a national "twelfth five-year" plan and improve the utilization efficiency of irrigation water resources, Ningxia has accelerate the pace of high standards of farmland construction of water conservancy facilities, including the lining of the canals at all levels to reduce the leakage loss of irrigation water. From field survey, irrigation efficiency of water resources utilization are improved significantly after a large number of canals were builted.However,due to Ningxia is located in the seasonal frozen field, the frost heaving damage is very serious to lining structure of canals.New anals new build will occur severe frost heave deformation damage and seepage water saving effect will greatly reduc after two or three years. The frost heaving damage of canals in Ningxia is especially serious, so, based on that fact, through the frost heaving research situation of canals, theory of frost heave and frost heave mechanics model, this article combined channel frost heave prototype observation and analysis of mechanical model and sum up the frost heave deformation factors of canals and varying patterns of frost heave deformation, ground temperature, frost heaving force. Above this,the lining structure internal force calculation was also included.Finally, considering the friction force between soil and canal lining plates, this paper exploratory puts forward the frost heaving mechanics model of composite lining u-shaped canals considering interface friction from soil, geomembrane and splicing double arc-plates, in order to reveal canals frost heaving substantive issues from the angle of mechanics.The main conclusions in this thesis are as follows:(1) The larger of size and the seams were more, the lining plate will appear more frost heaving cracks and the frost heave deformation is more serious. Different parts of the frost heave variation along the longitudinal change basically as same as the date change, frost heave variation of the same part along with the date presents the first increases and then decreases,the maximum value appeared around the middle of February, and then began to decrease.(2) With the increase of thermistors buried depth, ground temperature value is constantly increasing, the depth of 50-70cm ground temperature value is close to, less affected by temperature. Within 20cm depth ground temperature value’s change is bigger, greatly influenced by atmospheric temperature. (3) Frost heaving stress and the amount of frost heaving approximate number correlation in pairs, amount of frost heaving and frost heaving force is not a linear relationship. The greatest frost heaving stress value of bottom of canal and shady slope were 11.4kpa and 14.6kpa respectively, the frost heaving stress of sunny slope is 4.55 kpa. Frost heaving stress peak appeared in low temperature, and as the ground temperature rise again,frost heaving stress diminished gradually, both approximate linear relationship.The function relation between frost heaving force of bottom of canal and force ground temperature is:y= 0.432+0.1x; The function relation between frost heaving force of shady slope and ground temperature is:y= 0.88+2.5 x; As the ground temperature rise again, frost heaving force tend to be a stable value finally.(4) Through the indoor shear test of canal soil and geomembrane,composite geomembrane, concrete lining plate, calculated interface shear strength index of four kinds of materials:internal friction angle is 25.65°,32.72°,34.14° and 34.43° respectively, cohesive force is 12.25 kPa,30.64 kPa,39.74 kPa,31.46 kPa respectively, interface friction coefficient were 0.48,0.64,0.67,0.48, it can be seen that coefficient of friction of geomembrane, composite geomembrane with canal soil is less than concrete plate with canal soil.(5) By calculating the internal force of the concrete lining of two spelling u-shaped canal, the maximum tensile stress in the concrete lining structure is 2.8Mpa and the maximum tension stress is greater than the ultimate tensile stress of concrete slab 2.6Mpa, but the smaximum tensile stress in geomembrane lining structure is 2.39Mpa, so, this kind of composite lining can improve the ability of antifreeze of canals.