MODIFICATION OF DRUCKER-PRAGER CRITERION IN TENSILE SHEAR REGION
LI Ping¢en1，YIN Youquan2
(1. Institute of Geophysics，China Earthquake Administration，Beijing 100081，China； 2. Department of Mechanics and Engineering Science，Peking University，Beijing 100871，China)
Abstract：Drucker-Prager criterion(D-P criterion) has been widely used in the field of rock plastic mechanics. However，it is a type of compression shear yield criteria and not suitable for tensile shear stress states. According to this case，two feasible schemes are proposed to modify D-P criterion in tensile shear region. The first scheme is that the conical surface expression is still retained in compression shear region while in tensile shear region and its neighbor，a spherical yield surface is employed in place of the original conical surface near cone apex. The second scheme uses a hyperbolic rotating surface to approximately replace D-P conical surface. The modified new criteria defined by the two methods are called as D-P-Y criterions. They are three-parameter criteria and not only agree with the experimental result in triaxial compression test in compression shear stress states，but also can fit the tensile strength date in tensile shear regions. Meanwhile，the D-P-Y criteria are everywhere-smooth regular functions in all compression shear and tensile shear regions，and the constitutive equations can be established by using classic normality rule as well as consistency condition，needing no treating any singular points specially，which brings conveniences for application and programming. Particularly，for hyperbolic type D-P-Y criterion，when the relevant parameters are zero，it can be degenerated into D-P and Mises criterion，respectively. Therefore，it can be incorporated into D-P-Y criterion only in programming.
