Experimental Research on Mechanical Property of Phyllite Tunnel Surrounding Rock Under Different Moisture State

Based on the Tian Cheng tunnel engineering project, the phyllite are collected to analyze the cementation type and internal structure by powder X-ray diffraction and electron microscope through INSTRON-1346 electrohydraulic servo tester. In addition, physical properties test, uniaxial compression test and triaxial compression test under different moisture state to analyzes the mechanical property of phyllite. The results indicate: Poisson ratio of phyllite fluctuates from 0.15 to 0.25 when structural plane’s dip angles fluctuate. There are fewer connections between poisson ratio and the included angle between the structural surface and loading direction. The failure mode of phyllite under dry state are: shear failure and bedding slide occurs under uniaxial pressure; when the dip angle of structural surface is perpendicular to the axial force, under different confining pressure, main failure mode of samples is shear failure. When the confining pressure is 10 MPa, poisson ratio of sample increases and compressive strength and elastic modulus decline when the soaked time increases. The plastic yield behavior occurs before the peak stress and strain and strain softening occurs over the peak. The plastic yield degree and softening degree increase with the increase of the soak time.