Mechanism And Application Research Of Heat Preservation And Frost Heaving Of Canal In The Area Of Seasonal Frozen Soil In The North

Over the years,a large number of experimental research results in the lining channel frost heaving have been obtained in Hetao Irrigation District of Inner Mongolia,but there are few experimental studies on the anti-frost heave effect of polystyrene board with different thicknesses.In particular,there is no relevant research on the insulation effect of the molded bag concrete lining channel.In order to find out the thermal insulation mechanism and anti-frost heave effect of laying polystyrene board under the conditions of prefabricated plate and bag concrete,the base soil temperature,freezing depth,frost heaving,water content and groundwater level were studied under different heat treatment conditions,through the frost heaving test field and the prototype channel frost heave test.The following major innovative results are proposed:1.By sampling and testing the polystyrene board laid in the multi-year operation channel,it can be known that the apparent density decreased by 7.92%-23.33%;the thermal conductivity of the upper part of the slope increased by 19.44%?50%,the lower part increased by 86.11%?105.56%;the dimensional stability increased by 1?2 times,and the volumetric water absorption increased by 10.5?16.5 times.2.Through the field in-situ test,the insulation and anti-frost heave technology of the channel lining of polystyrene board in the Hetao Irrigation District was studied experimentally.It is concluded that,Laying 2?12cm polystyrene board under precast concrete slab,the total accumulated temperature is increased by 236.95%?563.84%,the frost heave rate is reduced by 53%?94.7%,and the frozen depth is reduced by 64.02%?75.98%.The unit thickness polystyrene board can increase the ground temperature by 0.88?,reduce the frost heave amount by 1.75 cm,and reduce the freezing depth by 9.24 cm.3.Through the frost heaving test of different mold bag concrete treatments,The molded bag concrete of unit thickness can increase the temperature by 0.16?,only 18.1%of the increase temperature of polystyrene board.The total accumulated temperature is increased by 3.93%?9.22%.When the 4?8cm polystyrene board is laid under the mold bag,the total accumulated temperature increases by 207.6%-272.3%,and the frost heave rate is reduced by 71.43%?96.6%.4.Through the establishment of the channel frost heave mechanics model,the main reasons for the frost heaving of the channel are discussed.The main parts of the frost heaving damage of the channel were analyzed,and the frost heaving damage of the typical channel was checked.Obtain that the maximum axial force and shear force of the channel board of trapezoidal channel are located at the foot of the channel slope.The maximum bending moment value of the channel slope board is located at the lower third of the channel slope.The maximum shear force on the bottom of the channel is located at the foot of the slope.The maximum bending moment of the bottom of the channel is located at 1/2 position of channel bottom.5.The suitable thickness of the polystyrene board in the lining channel of the Hetao Irrigation District was proposed.For the east-west precast concrete channel,the suitable thickness of polystyrene board of shady slope,sunny slope,bottom of the channel is 10cm?6cm and 8cm.For the north-south precast concrete channel,the suitable thickness of polystyrene board of slope and bottom of the channel is 8cm and 7cm.6.By establishing a typical channel numerical model,the finite element software ADINA was used to analyze the temperature gradient distribution and temperature increase effect of the foundation soil under the condition of laying 2-12cm polystyrene board.The warming effect of laying polystyrene board is most remarkable in the soil layer of 30cm or more.Laying more than 6cm polystyrene board can increase the insulation effect by more than 50%and reduce the frost heaving by more than 90%.7.Taking different groundwater level test platforms and prototype channels as research objects,the effects of groundwater level on frost heaving of base soil were analyzed.When the groundwater level is reduced by 0.5?1.0m,the frost heave rate is reduced by 71%?83.8%.