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Dilatancy and plastic strain characteristics of layered rock mass
under triaxial compressive test

TANG Kedong，WANG Jialiang，GUAN Junfeng，LI Lielie
（School of Civil Engineering and Communication，North China University of Water Resources and Electric Power，
Zhengzhou 450045，China）

Abstract： In order to study the dilatancy and plastic strain characteristics of layered rock， the phyllite
was made into samples with bedding angle of 0 degree，30 degree，45 degree，and 90 degree. The experi⁃
ments were conducted on MTS815 servo-controlled test machine，a coefficient is defined for qualitative anal⁃
ysis of the axial and circumferential crack named plastic strain ratio，the results show that the five typical
sections and characteristic stresses of the phyllite stress-strain curve change with the change of confining
pressure and loading direction， which is determined by the force mechanism of phyllite. The volumetric
strain corresponding to the dilatancy point of the phyllite is reduced as the confining pressure increases. Be⁃
sides， as the inclination increases， the axial strain and volumetric strain corresponding to the dilatancy
point decrease. Regardless of any bedding angle， the long-term cohesion of phyllite is generally greater
than the peak cohesion，and the long-term friction angle is generally less than the peak friction angle. The
development speed of axial fracture is faster than that of circumferential fracture under low confining pres⁃
sure， and the development speed of circumferential fracture under high confining pressure is significantly
faster with the increase of deviatoric stress.
Keywords：phyllite；dilatancy；triaxial compressive；experimental study；plastic deformation

（责任编辑：耿庆斋）

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