考虑胶结发挥的结构性弹黏塑性统一硬化模型

Bonding in structured soil decays with loading, however bonding effects exert with soil deformation development. Based on this recognition, this project plan to build a structured soil constitutive model considering bonding exertion rather than bonding itself. According to isotropic compression, one-dimensional compression, compression with constant stress ratio, compression with constant strain ratio, unconfined compression，triaxial compression and triaxial extension test data, a characteristic state function of soil structure considering jointly the void ratio, soil structure potential and unconfined compression strength is constructed. On this basis, bonding decay law is extracted, and bonding exertion variety is then built through referring the decaying bonding. Afterwards, the bonding exertion variety is introduced into yield function and plastic potential function reflecting the dynamic bonding influence. In the frame work of unified hardening (UH), a UH model of structured soil considering bonding exertion is planned to be built. In order to describe soil deformation in long term loading, the presented model is explored to consider time effects, and an elastic-viscous-plastic UH model of structured soil considering bonding exertion is then built. After that, the model is applied to three-dimensional stress states via transformed stress method. At last, the proposed model is planned to be embedded in finite element software and be applied to simulate the practical engineering.

结构性土中胶结随加载而单调衰减，但胶结的实际效果却随变形发展而逐步发挥。基于这一认识，本项目以胶结结构性土为研究对象，通过等向压缩、一维压缩、等应力比压缩、等应变比压缩、无侧限压缩和三轴压缩及拉伸试验探索胶结的发挥发展规律。根据试验结果，建立联合考虑胶结结构性土孔隙比、结构势、无侧限压缩强度的结构性特征状态函数。在此基础上，以随加载而单调衰减的胶结结构性作为动态参照，建立胶结发挥量的演化方程。继而将胶结发挥量引入屈服函数和塑性势函数。在统一硬化框架下，建立考虑胶结发挥的结构性统一硬化模型。为使模型能反映长期荷载作用下变形的时间效应，将所提模型与统一硬化框架下的弹黏塑性超固结模型相结合，发展建立考虑胶结发挥的结构性弹黏塑性统一硬化模型。而后，利用变换应力三维化方法将所提模型三维化以描述真实三维应力作用。最后，将模型子程序嵌入有限元软件模拟计算实际工程。

胶结结构性广泛存在于天然土中，显著影响土的受力变形特性。胶结结构性的发挥使得土体在加载初期表现出“强”与“硬”的假象，而在加载后期产生更为突然的剧烈变形，对实际工程产生不利影响。本项目基于胶结发挥对侧限压缩土体应力反馈的影响规律，建立了考虑胶结发挥影响的侧限压缩本构描述，实现对承受侧限压缩的结构性土全过程应力反馈的较合理描述。根据胶结结构性本构关系，揭示胶结结构性衰减所致应变软化及减压软化的本构描述机理。在统一硬化理论框架下，将旋转硬化增加考虑进结构性土模型，将结构性土统一硬化模型扩展至描述结构性土经历往复加载情形下，应力诱导各向异性的发展及对本构关系的影响。借鉴统一硬化理论对时间效应描述的思想，将其引入结构性土统一硬化模型，建立结构性弹黏塑性统一硬化模型，使其可合理描述结构性软土的率相关应力应变特性。此外，在研究中思考岩土本构理论中塑性广义剪应变的定义及物理内涵，指出其在弹塑性叠加以及塑性应变增量累加中的充分必要条件。上述关于胶结结构性土本构模型研究的阶段性成果，可为后续胶结结构性土本构理论研究扩展与推广延伸提供有力支持。