Experimental Study On The Mechanical Properties Of Intact Loess Considering The Effect Of Directional Moistening With Load

Loess is widely distributed in Northwest China.The unique soil forming environment conditions have brought up the unique macropore,underconsolidated structure and significant water sensitivity of the intact loess in this area.These characteristics make the undisturbed loess frequently cause various loess engineering geological disasters under the combined action of force and water;engineering accident cases such as collapse,landslide and liquefaction are common here.At present,the research is far from perfect on the influence of the combination of force and water on the engineering mechanical properties of intact loess,and more experimental studies are urgently needed to provide support.Based on the considerations above,this paper takes the intact loess from Yan'an as an example,conducts experimental research on the behaviors of deformation,shear strength and anisotropy of intact loess considering the effect of directional moistening with load through the moistening deformation test and moistening direct shear test under the condition of lateral limit,and makes regression analysis on the corresponding data.The main results are as follows:The results of the experimental study of moistening deformation show that: in the load holding moistening test after loading or unloading under the specified initial conditions,when the moisture content is fixed,the vertical load stress level has a positive correlation with the deformation amount and deformation duration of the soil sample;while when the vertical load is fixed,the deformation amount and deformation duration of the soil sample under different moisture content levels are significantly different,but the correlation is not obvious.The results of the experimental study on the moistening direct shear show that: there is no obvious strain softening in the loading and moistening direct shear,and there is obvious strain-softening in the unloading and moistening direct shear.The relationship between the ultimate shear stress and the moistening load-bearing stress of the soil basically has a significant positive linear correlation.The ultimate shear stresses are different under different moisture content.However,the influence of moisture content on the above shear strength indexes of soil samples is not obvious.The anisotropy of deformation and strength is studied by choosing different orientations during sample preparation.The results show that the deformation index and shear strength index of intact loess are obviously different related to the different orientation of sample preparation under the condition of certain load and certain moisture content,and the anisotropic ratio to measure this difference gradually tends to 1,which means the ideal isotropic state,with the increase of load and moisture content.On the basis of the experimental research above,this paper makes multivariate linear regression analyses on the influence of various factors in the combination of force and water on the deformation and shear strength characteristics of intact loess from the statistical point of view.The results show that: for the intact loess under the combined action of force and water,both the deformation characteristics and the shear strength characteristics are not simply considered as the influence of a single factor,but the comprehensive effect of various factors in the combined action.In this action,the dominant factor is the moistening load-bearing stress level,and the loading and unloading state of moistening load-bearing and the moisture content level play a secondary role,while the influence of sample preparation orientation is negligible to some extent.