Modified Duncan-Chang Model and Mechanics Parameter Determination Based on Triaxial Consolidated Drained Tests of Guiyang Red Clay in China

Abstract

A large area of China Southwest is covered by red clay, which is a kind of Karst regional special clay with high moisture content, high ductility, large void ratio, low density, poor compaction. Based on Duncan-Chang model, the constitutive model of red clay and its mechanical parameters are studied by laboratory tests and numerical simulation. (1) According to the results of triaxial consolidated drained tests with different moisture content, the damage forms, stress-strain curve, the relationships between pore water pressure and displacement changing with the time are analyzed in detail. (2) Based on Duncan-Chang model, the incremental elastic curve is fitted. The curve is composed of three segments which represent the deformation law of the clay samples in compression-shearing process. Correspondingly, the initial tangent elastic modulus is modified into a three-stage function, and the Duncan-Chang model of Guiyang red clay is obtained and the parameters such as shear strength, failure ratio, tangent Poisson’s ratio and tangent volume modulus are calculated. (3) VC++ programming language is used to modify Duncan-Chang E-B model in the software of FLAC^3D. The results show that the numerical simulation curve is in good agreement with the stress-strain curve of the experiments, which shows that the modified Duncan-Chang model has good feasibility and applicability to Guiyang red clay.