Experimental Study And Numerical Simulation Of Evaporation Characteristics Of Loess

Soil moisture is a key indicator of describing the degree of drought,and it is also the main basis for the utilization of water and soil resources,the decision-making of drought-resistant and disaster relief and afforestation vegetation selection.Surface evaporation,which is the main movement form of soil moisture,is one of the main processes of material and energy exchange for the soil-atmosphere,and it is also a direct factor inducing many geotechnical related problems.Therefore,analyzing the surface evaporation process,the movement process of soil and water and predicting the actual surface evaporation intensity have become important research directions for environmental geotechnical engineering.In this paper,the evaporation process of loess is studied by means of laboratory test,theoretical analysis and numerical simulation.The theoretical model of loess evaporation coefficient is established.The correctness and applicability of the evaporation model are verified by combining experimental data and numerical simulation.Three laboratory tests were carried out in this paper:the first group of tests was a laboratory evaporating dish test,and the potential evaporation intensity data for climatic conditions was collected for build the latent evaporation model;the second group of tests was the experiment of the influence of soil diameter on the evaporation intensity.The conclusion that the test data deviation is small in the range of 50mm-100mm;the third group of tests is the one-dimensional soil column evaporation test of loess,and the distribution of water content with time and the daily variation curve of evaporation intensity of one-dimensional loess column are obtained.The conclusion that the thickness of the main evaporation layer is 80 cm is obtained,and when the evaporation is substantially stable below 80 cm thickness,the water content is related to the plastic limit of the loess.Based on the above test results,the evaporation coefficient E_w/E₀ of loess soil was discussed,and the trend law of evaporation coefficient with time was analyzed based on experimental data.The existing models of potential evaporation intensity E₀and soil sample evaporation intensity E_w are discussed respectively.It is considered that Fu Baopu model is more suitable for engineering applications.The model of Fu Baopu was selected and the model parameters such as wilt coefficient w_f and soil evaporation layer thickness h were determined.The relationship between soil evaporation coefficient and water content was verified.The model was validated by comparison with experimental data.The loess evaporation model established in this paper is applied to the numerical calculation.Based on the GeoStudio finite element simulation software,the soil moisture Van Genuchten model and the calculation results of the Fu Baoyu model as the boundary conditions of soil evaporation,the water distribution law of shallow soil under the experimental conditions was analyzed,and the water content distribution of each stage in the test period was calculated.The calculated results are roughly consistent with the actual water content w distribution.The actual case was used for the calculation and analysis,and the curve distribution map was finally obtained.