Studying Of Sands Constitutive Model That Including The Influencing Factor Of Stress Path At Small Strain

Strain of soils in practice is most in small-strain region. The stress-strain behavior is markedly non-linear but very stiff and dependence on the stress path direction, strain fully recoverable but isn't instantaneous, which are the basic features of the stress-strain behavior of soils within small-strain region. Along these behavior, non-linear, very stiff and stiffness are decreasing with strain fast already can be expressed by some small-strain constitutive models, Effect of special stress path which direction is invariable can also be expressed by already existed small-strain constitutive models. However, effect that variable direction of stress path to stiffness can not be expressed by already existed small-strain constitutive models.In order to study the effect of the stress path direction on stiffness, by using of the standard triaxial stress path testing system imported from the GDS company of Britain, drained shear test were conducted on standard sands which are each isotropically and anisotropically consolidated at eight different stress paths, during the course of studying the effect of stress path, the effect of initial stress condition, stress path change and time are also studied.It can be found by analyzing the effect of stress path from test result, there are some rule existed in the line of the same strain, according to difference strain, the line of the same strain just like a circle, which we called it the same strain stress circle. By expressing the movement of the same strain stress circle, Young's modulus was conducted, which can display the effect of different stress path and variable of the direction of stress path, furthermore, Poisson's ratio that can consider the effect of stress path is also studied. Based on this, a small-strain constitutive model of sands was erected, which can express the effect of stress path. It's shown that this model not only can express the effect of stress path change, but also can express the behavior such as non-linear, very stiff and stiffness are decreasing with strain fast. The parameter of Young's modulus can be defined by three special stress path test and a simple ways to define the parameter of Young's modulus is also proposed, So it more easier than other small-strain model in using. When simulating to the test result in invariable special stress path, for the effect of use the supposition that the line of the same strain is a circle, model is not as good as other small-strain models, but it possessed a special function that other small-strain models is not possessed, it can express the stiffness change along any stress path direction, including the effect of variable direction of stress path.