Experimental Study On Mechanical And Hydraulic Characteristics Of Compacted And Lime-modified Loess

The Loess Plateau is the core area of Belt and Road Initiative strategy.Loess,as a typical unsaturated soil,has good engineering properties in natural state,but when it is humidified by rainfall or irrigation,the strength of loess often drops sharply and the deformation increases suddenly,that is,the water sensitivity of loess.Compaction treatment is often needed to improve the mechanical properties of loess foundation engineering,while higher requirements of foundation engineering need to take improvement measures.Therefore,it is of great practical significance to study the mechanical and hydraulic characteristics of compaction and improvement loess in order to grasp its engineering characteristics and solve the foundation engineering problems in loess area.In this paper,the compaction and lime modified loess in Yanundefinedan area are taken as the research object,and the loading and humidification tests are carried out under the condition of triaxial and lateral limiting stress,and the effects of moisture content and compaction degree on its mechanical and hydraulic characteristics are studied.The improvement effect of modifi ed loess is evaluated.The main research work and results of this paper are described below.Based on the isoaxial compression and consolidation-drainage triaxial compression test,the isotropic compression characteristics of compaction and moisture content and the effects of triaxial shear stress and strain,critical state and yield characteristics are analyzed,and the isoaxial compression yield stress and compression index are put forward.T he expression of the relationship between shear strength index and moisture content and compaction degree;It is revealed that the yield surface is an inclined ellipse on the plane of partial stress and average stress,and gradually expands outward with the increase of compactness and strain of plastic body and the decrease of moi,sture content.The average stiffness,failure deflection stress and shear strength index are used to evaluale the improvement effect of lime modified loess.Based on the controlled suction side limit compression test,the effects of the suction and the degree of compaction on the compression and humidifying deformation,the water volume and the soil water characteristics are analyzed,and the variation of the compression characteristics of the lateral and equal-direction stress conditions is analyzed.It is revealed that the ratio of the ratio of the ratio of the ratio of the ratio of the ratio of the ratio of the ratio of the ratio of the ratio of the ratio of the ratio of the ratio of the ratio of the pore to the compressive stress(the ratio of the vertical stress to the structure yield stress)under the condition of different water content and the degree of compaction has the property of reduction.Based on the graded humidification test under the condition of constant vertical stress,it is revealed that suction,net vertical stress,compaction degree,force-water path and humidification series have great influence on the humidification deformation characteristics,and the collapsibility coefficient measured by double-line method is larger than that measured by single-line method under different conditions.The influence of net vertical stress and compaction degree on soil water characteristics and seepage characteristics is analyzed,and it is revealed that the seepage coefficient of saturated lime modified loess is smaller than that of compacted loess under the same conditions.The relationship between saturation and suction and the relationship between seepage coefficient and saturation of compacted loess can be described by classical Van Genuchten soil water characteristics and seepage model respectively,and then a modified Van Genuchten model considering the influence of net vertical stress and compaction degree is proposed.