【作者】 赖勇；

【导师】 施建勇；

【作者基本信息】 河海大学 ， 岩土工程， 2005， 硕士

【摘要】 实际工程中土体的应变主要在小应变范围内,而应力应变关系高度非线性、具有很大的弹性模量、变形可完全恢复但又存在迟滞现象、弹性模量变化受应力路径的影响等是土体在小应变区域内的显著特征。在这些主要特征中,高度非线性、弹性模量大、弹性模量急剧变化等特征现有的小应变模型基本上都可以反映,固定方向的特殊应力路径条件下的应力路径的影响也能反映,但是,对于复杂应力条件下的应力路径的影响,现有的小应变模型不能反映。 为了研究小应变条件下应力路径对弹性模量的影响,采用GDS数字式应力控制三轴系统,以标准砂为试样,分别在等压固结和K₀固结条件下,取了8条不同的应力路径进行了小应变下的固结排水试验,在研究应力路径的影响的同时,也对初始应力状态的影响、应力路径旋转的影响和静置时间的作用进行了一些研究。 通过对当前应力路径的影响的试验结果进行分析,发现具有相同轴向应变的等值应力线存在一定的变化规律,对应不同应变的等值应力线可以假定为一系列的圆,称之为等值应力圆。通过刻画等值应力圆在应力空间的运动规律,推导出了标准砂在小应变下可以考虑应力路径方向变化这一复杂应力条件的割线杨氏弹性模量的计算公式,并对考虑应力路径影响的泊松比的计算方法进行了研究,建立了砂土在小应变下可以考虑应力路径影响的本构模型。模型除了可以反映应力路径方向变化的影响外,仍可以反映非线性、弹性模量大、弹性模量急剧变化等小应变的主要特征。模型的杨氏弹性模量方程参数可以由3个特殊应力路径方向的试验确定,也可以全部采用常规三轴试验来确定参数,所以参数的确定比一般的小应变模型要容易。在对一定的特殊应力路径进行模拟时,由于等值应力线形状假定带来的误差,模型模拟的效果要稍差一些,但多了可以反映任意应力路径包括应力路径方向变化的功能。更多还原

【Abstract】 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.更多还原