Study On Anti-frost Heave Measures Of Concrete Lined Canal Delivering Water In Winter

Xinjiang is located in seasonal permafrost area,due to perennial drought and water shortage,many diversion canals have been built for irrigation areas and hydropower stations.Among these canals,there is a kind of canal delivering water in winter.Such canals continue to carry water to power stations or cities in winter.Affected by the water in the canal,the moisture content of the base soil of such canals is generally higher than that of the water-stop canals in winter.Therefore,frost heave damage is more severe than that of water-stop canals in winter.Based on reading and analyzing a large number of domestic and foreign literatures,The research progress of mechanical model,finite element simulation,frost heave mechanism,failure characteristics and protective measures of canal delivering water in winter are described in detail.The main research work and results of this paper include the following:(1)Based on the finite element analysis theory and using ANSYS finite element software,the basic qualitative laws of temperature field,stress field and displacement field of frost heave of concrete lined of canal delivering water in winter without ice sheet in winter were deeply studied.Then,three anti-frost heave measures for canal delivering water in winter are proposed.They are thermal insulation and anti-frost heave measures for operation at high water level,polystyrene thermal insulation and anti-freeze heave measures and new anti-freeze heave measures for replacement,the temperature field,stress field and displacement field are simulated and the qualitative law of frost heave changes is deeply analyzed.(2)The general regular of temperature field,stress field and displacement field in canal with depth of 2 m,3 m and 4 m affected by negative temperature are studied.Variation regular of temperature field: When the water depth is different,the canal will produce huge temperature difference at the junction of air,water surface and lining slab,where the isotherm fluctuates strongly.Variation regular of stress field: When the water depth is different,the position of the maximum stress on the canal lining slab is at the junction of air,water surface and lining slab.With the increase of the water depth,the stress decreases gradually.Variation regular of displacement field: With the increase of water depth,the maximum frost heave displacement gradually decreases and shifts to the top of the canal.Finally,it is concluded that the reasonable water depth of the canal in winter is 4 m.(3)Numerical simulation of temperature field,stress field and displacement field of polystyrene thermal insulation and anti-frost heave measures for canal delivering water in winter shows that Variation regular of temperature field: The concrete lining slab in the horizontal direction of canal top within 1.5 m and above the water surface decreases.With the increase of the thickness of insulation slab,the freezing depth of canal decreases,but the decreasing extent decreases gradually.Variation regular of stress field: The maximum upper stress on the lining layer decreased by 48.23% when 8 cm thick polystyrene insulation board is added to the canal compared with that without insulation measures.It can be seen that the new polystyrene thermal insulation and frost heave protection structure can effectively reduce the stress on the concrete lining layer.With the increase of the thickness of thermal insulation board,the reduction of stress decreases gradually.Variation regular of displacement field:The maximum frost heave displacement of the canal after laying 8 cm thick polystyrene insulation board was reduced by 52.32% compared with that without anti-frost heave measures.It can be seen that the frost heave displacement of the canal can be greatly reduced by adopting the new anti-frost heave structure of polystyrene insulation.With the increase of the thickness of the insulation board,the displacement reduction range also decreases.Finally,the optimum thickness of insulation board is 14 cm.(4)The numerical simulation of temperature field,stress field and displacement field of canal delivering water in winter after the application of new anti-frost heave measures of replacement filling was found.Variation regular of temperature field: The maximum stress of the canal lining slab filled with 60 cm deep gravel soil is 78.78% lower than that of the canal lining slab without filling measures.Variation regular of displacement field: The maximum frost heave displacement of gravel soil with a depth of 60 cm was reduced by 41.8% compared with that without replacement measures,indicating that the replacement of gravel soil can effectively reduce the generation of frost heave displacement.Finally,the optimum filling depth is 120 cm.