多軸応力下における等方性および異方性岩石の破壊曲面について

概要

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A newly designed triaxial testing machine was used to investigate the ultimate strength of sandstone and crystalline schists under multiaxial stresses. Each specimen used was 5.5 cubic cm in sise, and the capacity of the testing machine was 200 tons vertically and 100 tons in each horizontal axis. The experiments were carried out under stress-controlled condition (8 tons/min). Rubber sheets with silicon grease were always used to minimize friction between the specimen and piston plate; thus the coefficient of friction could be reduced to 0.002. The unconfined compressive strength of sandstone was found to be σ_c=1 190 kg/cm^2 with variation of about ±3.9%. For the sake of non-dimensional representation of multiaxial test data, all the results are expressed as the value divide by σ_c. Introducing the principal stress parameter λ=(2σ_2-(σ_1+σ_3))/(σ_1-σ_3)(-1⥶σ⥶1), experimental results of the axial compression test (λ=-1) with high confining stress are in accordance with Mohr-Coulomb's failure criterion, deriving the strength parameters φ_0=33°40' and c_0/σ_c=0.46. The influence of the intermediate principal stress can be expressed by the following extended Mohr-Coulomb's criterion : [numerical formula] provided we choose the parameter α*=0.07. Under low confining stress, however, the experimental results deviate from the above criterion ; we cannot regard them as shear failure.
社団法人日本材料学会の論文
1971-02-15