Abstract:Based on the analysis of complete stress-strain curves for rock,and on the phenomenon that the reduction of elastic modulus and appearance of plastic strain happen simultaneously in the loading process,the basic hypothesis that elastic modulus and plastic strain are in direct proportion to damage is put forward. Based on the new conception of quasi-static damage process,the concepts of damage variable and release rate of damage strain energy are defined,and the relationship between them is analyzed. By the conservation of energy,the mathematical model of quasi-static damage process is brought forward. The dimensionless damage evolution equation and constitutive equation are set up and analyzed. The mathematical model set up in this paper includes only three constants,which are determined easily. The complete stress-strain curve is expressed with one damage evolution equation,whether for front or behind apex. The theoretical curve is in good agreement with the test result.