【作者】 李萌；

【导师】 罗汀；

【作者基本信息】 北京航空航天大学 ， 土木工程， 2010， 硕士

【摘要】 各向异性是天然土普遍存在的特性,可看作土体结构性的一种特例,它对土的变形和强度产生较大的影响,即沿着不同的方向加载时,将会产生不同的变形和强度的变化规律。本文在较为广泛的阅读和总结国内外已有的岩土各向异性强度和应力应变研究成果的基础上,通过超固结土的固结和三轴试验观察,深入地研究了岩土各向异性应力应变规律和破坏机制,给出了阐释和描述各向异性岩土强度的新准则。实际的天然土大多处于一般坐标下的物理空间中,而现有的各向异性强度准则大多建立在主应力空间中,且这些经典的强度准则都是在主应力轴方向不变的情况下推研出来的,这跟实际的情况有较大差距。本文通过主应力坐标轴与一般应力空间坐标轴的变换,使两个坐标系可以随意转动,来解决这一问题。Matsuoka等提出的空间滑动面准则是能够合理反映中主应力的影响较好的各项同性强度准则之一,且空间滑动面具有明确的物理意义。基于SMP,假定材料的摩擦角随沉积面和SMP的夹角而变化,通过主应力空间和物理空间的变换,将SMP的法向量变换到物理空间,以沉积面和SMP的最小夹角α为参数提出了一个各向异性峰值强度M_α。从而得到一个各向异性强度准则,适用于横观各向同性岩土材料,通过试验条件下的数据验证表明,该各向异性强度准则能够较好地描述各向异性土的强度变化规律。最后用试验验证了该各向异性强度准则的可行性。更多还原

【Abstract】 Naturally deposited soils are often found with the behavior of anisotropy,which can be treated as one of the structural characters of soils and has a great influence on stress-strain relationship and strengths of soils while loaded in different directions.Based on the study of previous research on anisotropic strength criterion and stress-strain relationship,this paper attempts to analyze the anisotropic failure mechanism of soils through tests observation and present a new criterion describing the anisotropic strength of soils.Most of the existing anisotropic strength criterions are constructed in the principal stress space,while natural soils are actually deposited in the physical space under general coordinates.Also these classic criterions are derived in the case of constant principal stress axes direction,which is inconsistent with the real situation.In this paper,in order to solve the problem,a transformation between the principal stress space axis and the general stress space axis is proposed to ensure that both coordinates can rotate freely.SMP(Spatially Mobilized Plane)criterion,proposed by Matsuoka et al.,is one of the isotropic strength criterions with specific physical definition and can well exhibit the impact of intermediate principle stress.Based on SMP criterion,a new failure criterion is proposed for anisotropic geomaterials.Through the the transformation between the principal stress space and the physical space,the normal vector of the SMP is transformed to the physical space.Assuming that the friction angle is changed with the angle between deposition surface and the SMP,a new expression of anisotropic peak strength Mα is proposed,which can represent the anisotropy associated with particles orientation distribution.Mα is the function of α which is the minimum angle between deposition surface and the SMP.The basic parameters can be obtained from the conventional triaxial tests of anisotropic soils.Verification by experiment data shows that the anisotropic strength criterion can be used to describe the anisotropy of soil strength variation.更多还原