(3) VC++ programming language is used to modify Duncan-Chang E-B model in the software of FLAC 3D. 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. The curve is composed of three segments which represent the deformation law of the clay samples in compression-shearing process. (2) Based on Duncan-Chang model, the incremental elastic curve is fitted. (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. Based on Duncan-Chang model, the constitutive model of red clay and its mechanical parameters are studied by laboratory tests and numerical simulation. These synthetic rock samples were subjected to the same loading and unloading paths as the real rock samples, and failed in the same mechanism as what was observed from the experiments, and thus it proved the validity of this numerical simulation with FLAC3D.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. Foliation planes of preferential orientations with respect to the primary loading direction were added to the synthetic rock samples to reflect the anisotropy of the gneiss. Various parameters were created to describe the physico-mechanical properties of the synthetic rock samples. The paper describes the FLAC3D simulations of the complex true-triaxial loading and unloading history of the different anisotropic samples. These tests have been used to validate a synthetic simulation using the Itasca FLAC3D numerical code. The results show expected patterns of weakness from preferentially oriented samples and highlight the importance of unloading history under true-triaxial conditions on the deformation and seismic response of the samples.
Samples were loaded under true-triaxial stress conditions and subjected to complex loading and unloading histories associated with rock deformation around underground openings. Isotropic pegmatite and gneiss have been used to systematically study the effect of anisotropy on the strength, behaviour and seismic response. A series of true-triaxial experiments have been carried out at the University of Toronto's Rock Fracture Dynamics Laboratory.
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