Study On Runway Subgrade Moisture-Heat-Stress Coupling Effect In Permafrost Regions

Four general airport clusters of Sanjiang Plain,Southeast Mountain Area,Songnen Plain,Da Hinggan Mountains and Xiao Hinggan Mountains are planned to form in Heilongjiang Province by 2030.A large area of permafrost distributes in area of Da Hinggan Mountains and Xiao Hinggan Mountains general airport group,and enormous difficulties in airport constructionare brought about by characteristic of permafrost.The stability of frozen subgrade is controlled by moisture,heat and stress,runway extremely easy to produce frost heaving and thawing settlement disease because of changes of water,heat and the stress redistribution caused by them.In addition,the influence of thermal disturbance on permafrost subgrade of airport runway is more significant because of structural characteristics of wide range of runway surface and runway can not be higher than surface of earth.However,theoretical and technical research on airport runway construction in permafrost region are still blank.Therefore,structural characteristics of airport runway are aimed at,methods of theoretical analysis,indoor model test and numerical simulation are used in this paper,moisture-heat-stress coupling effect of airport runway subgrade in permafrost region of Northeast China are analyzed,the basis for the construction and research of airport runway in permafrost region of Northeast China.Specific researches and results are as follows:1.The annual temperature variation model test of permafrost subgrade in Northeast China is carried out by using cryogenic lab,the law of temperature variation at different depths of permafrost subgrade is obtained when the ambient temperature changes.At the same time,corresponding finite element model of moisture-heat coupling is established,and its validity and reliability are verified.2.A three-dimensional finite element model of airport runway moisture-heat coupling subgrade in Northeast permafrost region is established,temperature field in central,end and longitudinal section of runway is analyzed and compared.It is found that the temperature field in end of runway is better than that in central,and construction suggestions of temperature control measures are put forward based on this.At the same time,simulation results of three-dimensional and two-dimensional symmetric model are compared.It is found that two-dimensional symmetric model can be used instead of three-dimensional model inresearch.3.The boundary layer parameters of permafrost region in Northeast China are studied by finite element simulation,and calculation formulas of boundary layer parameters in permafrost region of Northeast China are established.4.Moisture-heat-stress fields of airport runway subgrade finite element model in Northeast permafrost region is established,distribution and variation of temperature stress are analyzed.It is found that temperature stress should be considered in runway design,higher strength pavement materials should be selected as far as possible.During the operation of runway,especially in summer and winter,pavement condition should be observed in time,thawing and net-shaped crack should be paid special attention to.