The Research On The Land Surface Evapotranspiration Of Losses&the Laws Of Soil Water Movement In Arid Environment

Surface evaporation occupies an important place in water balance and energybalance, which not only relates to the conservation and loss of soil water andsalinization of soil, but also brings about significant impact on strength, deformationand infiltration of roadbase as well as selection of plants in geotechnical engineering,besides, it may bring about problems concerning the stability of side slope, seasonalswelling-shrinkage and deformation of ground and collapse of roadbase. Moreover, it isan important boundary condition in calculation of water field in shallow soil. Therefore,this paper explores to find method to determine evaporation capacity on loess surfaceand themoisture movement law in shallow soil in drought conditions by adopting thecombination of indoor and outdoor tests with numerical computation.First, by simulating surface evaporation of unsaturated loess, a series ofevaporating tests indoor and outdoor on a variety of soil samples with various initialmoisture and dry density were carried out. Based on the test results, the paper analyzesthe results of indoor and outdoor experiments and discusses the diversity of thoseexperimenting results. In addition, there is a considerable difference in the evaporationintensity and potential evaporation between indoor and outdoor tests, but a littledifference in the evaporation coefficient of them.Secondly, the paper explores the moisture migration rule of the soil samples. It isconcluded that the evaporation coefficient is closely related to the water content, andslightly affected by the dry density; The evaporation coefficient of the uniform soil with different initial moisture content reduces exponentially over time, thus forming arelation expressing the time-varying evaporation coefficient of soil of different initialmoisture. It is further revealed that the soil evaporation coefficient at any time is mainlyrelated to the water content of land surface and the moisture content gradient of theshallow soil. Based on the test data, a formula which contains the water content of thesoil surface and the moisture content gradient of the shallow soil is built in order todetermine the soil evaporation coefficient.Finally, based on the test results, it is established the calculation model of theshallow soil moisture movement under the evaporation condition, and then the implicitscheme method is used to solve the numerical calculation, the process of which isrealized by using Fortran Language. Compared with the test result is consistent．Thenumerical result is satisfactory．...