Study On The Deformation And Strength Characteristic Of Remolding Loess By True Triaxial Test

Loess is widely distributed in China, but mainly in the central and western regions. With the development of the western development of urbanization, constructions in the loess region becomes more and more, so studying on the strength for the deformation of loess will be of great help for promoting economic development in central and western regions. Conventional triaxial is widely used for the loess research for most, but in fact soil is almost in a very complex stress state, also, the dry density as well as water content always influences the strength of the deformation of loess, but due to limitations of experimental conditions such as conventional test equipment which can not simulate the ture stress state of the actual project or subgrade soil foundation. It is very important to simulation the real stress of loess and find how the dry density and water content effect the strength for the deformation of loess. Expanding the research on loess under complex conditions of initial stress, is not only good for improving the mechanical theory, guiding the engineering design and construction, but also is of great importance and significance.In this paper, TS-526 multifunction triaxial apparatus is used for true triaxial test under different dry density, water content, ways of consolidation and stress path.In this test, the effect on strength of deformation of loess by water content and dry density under different condition is studied, the conclusion can be drawn as follows:(1) The relation of stress-strain of loess is a hyperbolic type, and shows tough type, also the bias stress increases with strain.(2) Water content and dry density are the important factors influencing the soil deformation. For example, the bias stress increases when reaching the same strain with the increase of the dry density if water content keeps constant. The bias stress becomes low when reaching the same strain with the increase of the water content if the dry density keeps constant. Water content and dry density affect the structure of remodeling loess differently.(3) In the condition of the selected certain water content and dry density, applying different stress paths for the remodeling loess affects the deformation and strength largely. By changing the value of b and applying different stress paths, the relation of stress-strain is changing with b, and the bias stress is increasing with b. That is to say, the higher the b, the greater breaking stress applying to the loess sample is.(4) In the process of shearing, the axial strain is constantly increasing along with the major principal stress, indicating the axial direction has been compressed; minor principal stress direction is also decreasing along with the stress imposed, slowly at the beginning and begain to accelerate to destruction; the change of intermediate principal stress is more complex, at the beginning, it increases with the major principal stress, during this stage the sample has been compressed, the expansion degree and the turning point are decided by dry density, water content, consolidation stress and value of b, the larger the b, the greater the compression is, and the greater the strain at turning point is; the change of sample volume is firstly increasing and then decreasing, the level of reducing is decided by the swelling degree of the minor principal stress.(5) The strength envelope under different values of b for remodeling loess in different P-q planes changes linearly, and the envelope intersect at one point. The strength curves of different intermediate principal stress inπplane are different hexagonals. And its stress space expanses with the increase of the consolidation stress under the same water content, also, it becomes smaller with the increase of water content under the same consolidation stress.