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Research on modified Duncan-Chang Model for strong structured clay
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摘要: 土体的力学特性受结构性影响十分显著，结构性越强，破坏后变形越大，对实际工程影响越显著。目前对结构性土的特殊工程性质已有广泛认识，但如何用数学方法准确描述其强度和变形间的关系仍是主要研究内容。对分布在云南昭通地区的强结构性黏土进行了试验研究，结果表明：其结构屈服应力高达800 kPa，属于典型的强结构性土。根据常规三轴试验的应力-应变关系，将强结构性黏土的剪切变形划分为结构未破坏阶段、结构逐渐破坏阶段和结构完全破坏阶段；基于破坏过程，对传统邓肯-张模型进行修正，引入损伤比参数，建立适用于强结构性黏土的修正邓肯-张本构模型。对模型中的初始剪切模量、主应力差渐进值和剪切模量参数进行推导分析，各参数值与试验的土体剪切变形规律相符合；对已有结构性土的试验数据进行拟合分析，结果表明该修正模型可以较好地描述强结构性黏土的应力-应变特性规律。Abstract: The mechanical properties of soil are significantly influenced by the structure: the stronger the structure is, the greater the deformation of the soil damage is, and the more significant the impact on the actual project is. At present, the special engineering properties of structural soil have been widely understood, but how to accurately describe the relationship between strength and deformation by mathematical methods is still the main research content. In this research, an experimental study is carried out on the strong structural clay distributed in Zhaotong, Yunnan. The results show that the structural yield stress is as high as 800 kPa, which is a typical strong structured soil. According to the stress-strain relationship of the conventional triaxial tests, the shear deformation of strong structural clay is divided into structural non-failure stage, structural gradual failure stage and structural complete failure stage. Based on the failure process, the traditional Duncan-Chang model is modified and the damage ratio parameter is introduced to establish a modified Duncan-Chang constitutive model suitable for strong structural clay. The initial shear modulus, the asymptotic value of the principal stress difference and the shear modulus parameters in the model are deduced and analyzed, and the parameter values are consistent with the shear deformation law of the experimental soil. Through fitting and analyzing the experimental data of existing structured soil, the results show that the modified model can better describe the stress-strain characteristics of strong structural clay.
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图 3 不同固结围压下的应力-应变关系曲线
Figure 3. Stress-strain relationship curves under different consolidation confining pressures
图 5 强结构性黏土εl /(σ1−σ3)-εl关系
Figure 5. Relationship between εl /(σ1−σ3)-εl of strong structural clay
图 6 强结构性黏土εl /(σ1−σ3)-εl关系曲线示意
Figure 6. Schematic diagram of relation curve between εl/(σ1−σ3)-εl of strong structural clay
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