Study On Theoretical Prediction And Experiment Of Unsaturated Loess Soil Water Characteristic Curve

The soil-water characteristic curve is used to describe the relationship between the suction and moisture content in unsaturated soils.It can reflect the hydraulic and mechanical properties when the soil is in a non-saturated state,therefore,it is widely used in many fields of unsaturated soil mechanics,such as Penetration theory,adsorption theory,shear strength,etc.Currently the methods of determining soil-water characteristic curves include direct test and indirect theoretical prediction.Compared with direct measurement methods,which is time-consuming and uneconomical,indirect method is much faster and more economical.Therefore,indirectly predicting the soil-water characteristic curve through theory is even more popular.Based on such background,this paper is to study how to predict the soil-water characteristic curve with the fractal model,and then make comparison with the curve got through direct test.Based on their proximity,it can be judged that whether the soil-water characteristic curve can be obtained with the fractal model prediction.The following main conclusions are drawn in this paper:1?It can be concluded that the slope of the soil-water characteristic curve of the remolded and undisturbed loess changes from steep to slow.For different initial dry densities loess,low initial dry-density slope of the curve in the low suction segment soil sample is steeper than that of the high initial dry-density soil sample,whereas the residual moisture content is lower than that of the high initial dry density soil sample,indicating that its water holding capacity is poor.2?The fractal dimension of remolded loess obtained by electron microscopy scanning experiment is smaller to that of the original loess,with the maximum difference between them is about 0.1.This is because the structure of the remolded loess is greatly disturbed,resulting in the soil being loosened.Therefore,it can be inferred that the fractal dimension is related to the degree of compaction of the soil.The fractal dimension of the remolded loess obtained from the laser particle size analysis test is still smaller than that of the original loess,but the difference between them is small.Because the remolded loess was reshaped with the original loess and the particle size distribution did not change.Therefore,the particle size distribution measured by the laser particle size test was almost the same,so the final fractal dimension of loess was also similar.3?A comparison of the measured and predicted values of the remolded and undisturbed loess soil-water characteristic curves shows that all the trend of the comparison curve is that the predicted value is higher than the measured value first,and then lower than the measured value.The magnitude of suction at the intersection point illustrates that the intersection is connected to the fractal dimension of loess.The greater the fractal dimension of loess is,the greater the suction at the intersection will be.Moreover,through analyzing the closeness between the measured and predicted curves,it can be found that the fractal dimension of loess is related to the fractal dimension of loess with greater fractal dimension mapping higher degree of proximity.4?The actual and remodeling loess measurement and predicted soil-water characteristic curve is approximate,especially the actual measurement of the original loess is very close to the predicted curve.Except for sample 2,the other predicted values of the soil-water characteristic curves of the three samples are very close to each other and almost coincide with each other,which indicates that the prediction results of the two models are reliable.Therefore,by analyzing the closeness of the measured and predicted soil-water characteristic curves of loess,it can be inferred that it is feasible to replace the direct test with fractal models to determine the loess soil-water characteristic curve.