考虑胶结作用的木质素固化粉土边界面塑性模型

Boundary surface plasticity model for lignin-treated silt considering cementation

为研究木质素固化粉土的应力–应变特性,通过无侧限抗压强度试验和微观结构分析,探讨木质素固化土的胶结特性。基于边界面塑性理论,引入硬化参数、应力剪胀参数和胶结破坏速率等参数,提出考虑胶结作用的木质素固化土边界面塑性模型,采用非相关联流动法则和改进映射法则描述土体的不同破坏模式,并阐述模型中各参数的意义及计算方法。根据室内固结试验和三轴压缩试验,对木质素固化粉土的应力–应变、应力剪胀和超孔隙水压力变化特征进行分析,并验证了本文所提模型的有效性。研究表明:木质素产生的胶结作用是土体工程性质改善的主要原因之一;12%掺量木质素固化土屈服应力和不排水抗剪强度较素土分别提高约90%和40%,高、低围压下土体应力剪胀特性不同,围压对超孔隙水压力的变化影响较大;通过试验验证了模型计算的准确性,该模型可描述土体在不同受力状态下的应变特征,具有原理简单,参数明确的特点,可为固化土应力–应变的数值计算提供相应的理论基础。

To investigate the stress-strain characteristics of lignin-treated silt, the cementation properties of lignin-stabilized soil are discussed based on the results of unconfined compression strength tests and the microstructural analysis. Based on the boundary surface plasticity theory, the parameters of hardening, stress dilatancy and destruction rate of bounding effect are proposed to develop a new boundary surface plasticity model for the lignin-treated silt considering cementation. The non-associated flow rule and the modified imaging rule are introduced to capture different failure modes of stabilized soil, and the meaning and calculation methods of the parameters are also explained. The characteristics of stress-strain, stress dilatancy and excess pore pressure change for the lignin-stabilized silt are analyzed based on the results of consolidation tests and triaxial compression tests in the laboratory, and the validity of the proposed model is also verified. The results show that the reason for the engineering properties of the improved silt is the cementation introduced by lignin. The yield stress and undrained shear strength of lignin-treated silt with additive content of 12% are increased by about 90% and 40%, respectively. The characteristics of stress dilatancy and excess pore pressure are different under different confining stresses. The model results are consistent with the laboratory test ones, and the model can successfully capture the characteristics of stress-strain. The proposed model has advantages of clear principle and simple parameters, and it may provide a theoretical basis for the numerical computation of stabilized soil.