岩土的一种强度准则及其变换应力法

基于岩土摩擦性,假设岩土破坏是由其物理空间内特征面上的应力比决定,提出了等效应力比的概念,即物理空间特征面上的剪应力合力与正应力合力的比值.在二维条件下,等效应力比可表示为σ-τ坐标系下与摩尔圆相切的直线扣除截距正切值;在三维条件下,假设在XYZ空间内存在一三维物理空间平面,此三维空间特征平面的等效应力比为影响材料强度特性的决定性因素,基于上述三维空间特征面建立了强度准则并称之为a准则.SMP准则以及广义Mises准则都是a准则的特例,当二维坐标中的截距为零时,则强度准则退化为SMP(spatially mobilized plane)强度准则,而当正切角为零时,则强度准则退化为广义Mises准则.而当截距与外切角均不为零时,则强度准则为介于上述两者之间的一种强度准则,在偏平面上为介于SMP曲边三角形与广义Mises圆形之间的曲边三角形.在子午面上,采用考虑岩土压剪耦合的屈服准则,破坏准则采用幂函数表达式.在偏平面上提出了基于a准则的形状函数,并采用真三维应力状态表示的破坏强度准则表示在三轴压缩路径下以p,q二维应力变量表达的准则公式,推导得到了基于a准则的变换应力公式,可简单地将一般以p,q为基本变量的二维模型转变为三维应力模型.通过强度以及多种应力路径的测试对比,验证了a准则及基于该准则的变换应力公式的合理性.

A KIND OF STRENGTH AND YIELD CRITERION FOR GEOMATERIALS AND ITS TRANSFORMATION STRESS METHOD

It is assumed that the failure of geomaterials is determined by stress ratio between shear stress and normal stress on the characteristic surface based on its friction behavior. The concept of effective stress ratio is proposed and it is expressed by the ratio between shear stress and normal stress on characteristic surface. The stress ratio on characteristic surface can be expressed as the tangent value of straight line deducted by the intercept circumscribing the mohr's circle inσ-τcoordinates in two-dimensional condition. It is assumed that there is a three-dimensional physical space plane in XYZ space considering every two adjacent physical coordinate plane under three-dimensional space. The shear stress ratio on characteristic surface in three-dimensional space is the determinant factor influencing the failure behavior of material and the proposed criterion can be signed as a criterion. SMP (spatially mobilized plane) criterion and generalized Misescriterion are two special cases of the a criterion. When the value of intercept in two-coordinates is zero, the proposed criterion is degenerated to SMP criterion. When the value of tangent is zero, the proposed criterion is degenerated to generalized Mises criterion. When the intercept and angle of circumscribing line are not zero, the proposed criterion in deviatoric plane is between the above those. The curved triangular form is exhibited between the curves of SMP criterion and generalized Mises criterion in deviatoric plane. A coupling of compression and shear behavior yield criterion is adopted and a power function is adopted as failure criterion. A shape function is proposed based on the proposed criterion in deviatoric plane. The criterion expressed by p and q is substituted by the proposed criterion expressed by three dimensional stresses and the transformation stress equations are deduced based on proposed criterion. In general a constitutive model expressed by p and q can be converted as a thredimensional model simply. Through yield and strength behaviors and a variety of stress paths test contrast, the rationality of the proposed criterion and transformation method are verified.