Study On Strength Property Of Unsaturated Remoulded Loess

Loess is the mainly regional soil in northwest China. It is widely used in various engineering constructions, so its mechanical strength properties decide the normal use of constructions, decide the correct engineering design and foundation treatment. Otherwise, further study on loess has practical and theoretical significance as it has special engineering properties , which is different from common soils .The tri-axial tests of unsaturated remolded loess were performed for different dry densities and water contents and consolidation degrees using Yangling loess. The change laws of strength property and parameters of Duncan-Chang model of unsaturated remolded loess were analyzed.As the result of the test shows:The cohesion increases with increase of dry density, has exponent relation to dry density; decreases with increase of water content, has negative exponent relation to the water content; increases with increase of consolidation degree, has linear relation to consolidation degree. The inner friction angle increases with increase of dry density and consolidation degree, its increasing extent is bigger when U>70%; decreases with increase of water content, is nearly linear with water content.As the dry density's increasing, the stress-strain relationship curves change from the strain hardening into the strain softening type,and volumetric strain change from shrink into dilatation phenomenon, and the strain hardening and shrink phenomenon was more obviously with the increasing of confining pressure; the phenomenon with the water content's increasing is contrary to the dry density.Change laws of parameters of Duncan-Chang model can summarized as followings:Initial tangent modulus increases with increase of confining pressure, decreases with increase of water content, has negative exponent relation to the water content; increases with increase of dry density, has exponent relation to the dry density; increases with increase of consolidation degree.The range of damage ratio is 0.8～0.95; damage ratio increases with increase of water content, increases at first then decreases with increase of dry density; the dry density where turning point of damage ratio appeared is bigger under bigger water content. Damage ratio increases with increase of consolidation degree under lower dry density and decreases under higher dry density.Change law between Poisson ratio and initial conditions is complex: Poisson ratio increases at first then decreases with increase of confining pressure under lower water content and higher dry density, and decreases with the increase of confining pressure under lower water content and lower dry density or higher water content;νi100 increases at first then decreases with increase of water content under higher dry density and decreases with increase of water content in other conditions;νi under higher water content andνi300 in other conditions increase with increase of dry density;νi100andνi200 increase at first then decrease with increase of dry density under lower water content.Laws of material parameters K,K b,G,F change with initial conditions are obviously: K,K b increase with increase of dry density and consolidation degree, decrease with increase of water content; the change law of G is same withνi100; F is smaller in lower water content or saturation under bigger dry densities, F increases with increase of dry density and consolidation degree, decreases with increase of water content; there is no obvious change law with initial conditions.