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Abstract Compared with the classical elasticity theory，couple stresses theory considering the rotation of the micro structure of the gradient(i. e.，bending curvature)，can show effects of bending deformation. The meshless method and the couple stress theory were combined together. Discrete model of element-free Galerkin method based on couple stresses theory was provided. The maximum circumferential tensile stress crack propagation criterion was adopted. The crack-I plane problem in tension was studied to determine the basic parameters of the method and to solve the key technology of the algorithm application. The initial rupture of crack in rock mass under compression was studied with different micro scales. And then crack growth trace in rock mass loaded compressive stress was numerically simulated with a given micro scale. The results indicate that the couple stresses have no effect on crack-I and a significant influence on complex crack bending propagation. For complex crack，crack propagation angle，crack propagation steps and crack propagation load show remarkable scale effects.
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Received: 20 March 2009
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