Experimental Study On Reinforced Loess Under True Triaxial Experiment

In recent years, reinforced earth as a composed structure, has been widely used in highway,water transport, water conservancy, railways and other kinds of civil engineering, and obtained very extensive social, environmental and economic benefits. At present, both engineering and academics in many countries have carried out a mount of experimental researches on reinforced earth, but the study of reinforcement mechanism is still not clear, calculation method is not full-blown, and the theory study is obviously behind of engineering practice. Until now, almost all the experimental studies on reinforced earth put forward are based on conventional triaxil test. So in order to simulate the real stress state, it is necessary to study the regular pattern of the strength and the deformation on reinforced earth under three dimensional condition. Expanding the research on reinforced earth under complex conditions of initial stress, is not only good for improving the mechanical theory, but also is of great significance of guiding the engineering design and construction.In this paper, TS-526 multifunction triaxial apparatus is used for true triaxial test. It mainly discusses the effect of deformation strength characteristics of reinforced earth under different reinforced geogrid layers, different initial moisture content, different initial dry density, different consolidation confining pressure and different intermediate principal stress ratio b. The following conclusions are mainly obtained:(1) The relation curve of stress-strain of reinforced earth appears as hyperbolic type, and shows tough type. In addition, the bias stress increases with strain.(2) As other conditions are indentified, the ratio b can not improve the strength of the reinforced earth obviously when the reinforced geogrid layers are much more, and the integrity of the soil is reduced on the contrary. So it is not the more reinforced geogrid layers become, the better the strength is.(3) Initial moisture content and initial dry density are the important factors influencing the reinforced earth deformation. For example, when the moisture content keeps constant, the bias stress increases with the increase of the dry density when reaching the same strain. The bias stress becomes low when reaching the same strain with the increase of the water content if the dry density keeps constant.(4) Under the same initial conditions, as the consolidation confining pressure is lower, ratio b can affect the soil more obviously, and with the in increase of ratio b the strength of soil increased most. When the consolidation confining pressure is bigger, the strength of soil increases little with the increase of ratio b.(5) Intermediate principal strain increases with the increase of b when reaching the same axial strain. b=0.5 is the critical point of compression and inflation in the later shear test. Minor principal strain decreases with the increase of b. Minor principal stress direction is increasing, and it is more obvious when reinforced geogrid layers are used less.(6) The change of reinforced earth cohesion is more significant than internal friction comparing with unreinforced earth. The biggest cohesion and internal friction reach the highest point when the b is up to 0.25 when reinforced geogrid layers keep constant.