Biography
Prof. Feng Dai
Prof. Feng Dai
Sichuan University, China
Title: Deformation Failure Mechanism and Damage Constitutive Model of Jointed Rock Masses under Cyclic Uniaxial Compression
Abstract: 
Intermittent jointed rocks, widely existingin many mining and civil engineering structures, are quitesusceptible to cyclic loading. Understanding the fatiguemechanism of jointed rocks is vital to the rational designand the long-term stability analysis of rock structures.In this keynote, we systematically reported our recent experimental, numerical and theoretical investigations in this regard.First,the fatigue mechanical properties of jointedrock models under different cyclic conditions are experimentallyinvestigated, considering four loadingfrequencies, four maximum stresses, and four amplitudes. Underlower loading frequency or higher maximum stress andamplitude, the jointed specimen is characterized by higherfatigue deformation moduli and higher dissipated hysteresisenergy, resulting in higher cumulative damage and lowerfatigue life.Second,the influences of typical joint geometry (i.e., dip angle, persistency, densityand spacing) on the fatigue failure behavior of jointedrock models are estimated, andthefatigue progressive failure processes of the jointed model are numerically revealed. Two final failure modes are observed in the present study, i.e., tensile splitting failure and tensile-shear mixed failure. As the joint geometryparameter increases, the failure mode of jointed rocks gradually change from tensile splitting failure to mixed failure.Third, a damage constitutive model is proposed to describe the deformation and strength characteristics of intermittentjointed rocks under cyclic uniaxial compression. Our new model comprehensively reflects the coupled damage induced by micro-flaws and macro-joints,which is able to reliably reproduce the hysteretic stress-strain curves and the cumulative fatigue plasticdeformation of rock materials under cyclic loading.