考虑原状土初始应力状态的修正SMP屈服准则

A modified SMP yield criterion for undisturbed soil considering initial stress state

原状土与重塑土力学性质方面的差异性,来源于两者初始应力状态的不同及由此引起的结构性差异。重塑土的屈服曲面以等倾线为基线,原状土由于在形成过程中处于三向不等压状态,故其屈服曲面应以K0固结线(初始应力线)为基线。基于松冈-中井的空间滑动面屈服准则,在考虑初始K0固结状态的基础上给出了适用于原状土的修正SMP屈服准则。修正SMP屈服面由常规SMP屈服面绕位于σ2Oσ3平面上的直线σ2=-σ3旋转得到,旋转的角度等于等倾线与K0固结线之间的夹角。与在子午面和π平面上研究重塑土的屈服行为类似,研究原状土的屈服应该在通过K0固结线的子午面和通过σ1+K0σ2+K0σ3=c的χ平面上进行。针对砂雨法试样的真三轴实验结果计算表明,与常规SMP屈服准则相比,基于K0固结线的修正SMP屈服准则更适合描述自然沉积土的强度和屈服特征。

The differences in mechanical properties between undisturbed soil and remolded soil are derived from the diverse initial stress state and the corresponding structure distinctions. In the constitutive model for remolded soil constructed usually in the spherical stress state,the isoclinic line is utilized as the baseline of the yield surface. On the contrary,the K0-consolidation line（ or initial stress line） should be taken as the baseline of the constitutive model for undisturbed soil due to anisobaric stress state in space during settlement process. Based on the Matsuoka-Nakai ＇s SMP yield criterion a modified criterion considering the K0-consolidation is proposed. The modified SMP yield surface can be obtained by rotating the conventional SMP yield surface around the line of σ1/0 = σ2=- σ3for an angle of ω between the isoclinic line and the K0-consolidation line. Similar to the meridian plane and π plane in the yield surface for remolded soil,the meridian plane through the K0-consolidation line and the χ plane vertical to the K0-consolidation line can be employed to study the undisturbed soil. True triaxial test results of the pluviating sand sample indicate that the modified SMP yield criterion is superior to the conventional SMP yield criterion and is more effective in fitting the strength and yield characteristics of natural sedimentary soils.