土工格室加筋粗粒土的非线性剪胀模型及其有限元实现

Nonlinear shear expansion model forgeocell reinforced coarse-grained soil and its finite element implementation

关键词:  土工格室  粗粒土  二次开发  UMAT子程序  加筋效能

Key words:  geocell  coarse-grained soil  secondary development  UMAT subroutine  reinforcement effectiveness

摘要:

为了克服当前土工格室加筋粗粒土模型不足及其有限元分析方法的局限性,基于3参数非线性剪胀模型及土工格室加筋附加约束围压作用机理,提出了土工格室加筋粗粒土的非线性剪胀模型,此外,利用ABAQUS软件提供的用户自定义材料子程序UMAT接口,开发出了该模型的子程序,分别将应变软化型和应变硬化型的土工格室加筋砂土三轴试验结果与该模型模拟结果进行了对比验证,并进一步把加筋土整体模型与筋土分离式模型的计算结果进行了对比分析,同时还将土工格室参数对粗粒土加筋效能的发挥水平进行了评估。结果表明:构建的加筋粗粒土模型,能够精准地模拟并反映土工格室加筋粗粒土在受力过程中的剪胀性特征及其复杂的非线性力学行为；该模型数值模拟结果可以准确地预测不同强度类型土工格室强度在不同围压和砂土相对密度条件下的应力应变曲线关系；加筋土整体模型在达峰值强度及之前阶段,计算精度与分离式模型基本相当,另外,其还具有建模简便、计算高效的优势；同时,加筋土整体模型解决了分离式模型无法算出土工格室内填土达Mohr-Coulomb屈服函数破坏的难题。研究结果对于土工格室加筋土结构的数值分析领域具有重要的价值,可推动其在工程实践中的应用。

Abstract:

In order to overcome the inadequacy of the current geocell reinforced coarse-grained soil constitutive model and the limitations of its finite element analysis method. Based on the three-parameter nonlinear shear expansion model and the mechanism of geocell reinforced additional constraints surrounding the pressure action, a nonlinear shear expansion model for geocell reinforced coarse-grained soil is proposed. In addition, a subroutine for the model was developed using the user-defined material subroutine UMAT interface provided by ABAQUS software. The triaxial test results of strain-softened and strain-hardened geocell-reinforced sandy soils were compared and verified with the simulation results of the model, respectively, and the computational results of the reinforced composite model in this paper were further compared and analyzed with those of the reinforced-soil-separated model. The level of performance of geocell parameters on the reinforcing effectiveness of coarse-grained soil was also evaluated. The results show that the constructed reinforced coarse-grained soil model can accurately simulate and reflect the shear expansibility characteristics of geocell-reinforced coarse-grained soil during the stressing process and its complex nonlinear mechanical behavior. Through the secondary development of this model, it can accurately predict the stress-strain curve relationship of different degree types of geocell strength under different perimeter pressures and relative density conditions of sand and soil. In the stage of reaching peak strength and before, the calculation accuracy of the reinforced composite model is basically comparable to that of the separated model, and it also has the advantages of simple modeling and efficient calculation. At the same time, the reinforced composite model solves the problem that the separated model cannot calculate the damage of the fill in geocells up to the Mohr-Coulomb yield function. The results of this research are of great value to the field of numerical analysis of geocell reinforced soil structures and can promote their application in engineering practice.