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Abstract In order to obtain the reliable damage strength and the evolution regulation，an experimental scheme of synchronic testing of stress-strain curves，AE activity and velocity of P wave is proposed and carried out. Compared with the results from three different methods，besides AE and P velocity testing method，the characteristic strengths can be objectively obtained from stress-volumetric strain (including crack volumetric strain) curves. By defining the irreversibly accumulative crack strain as damage parameter from loading and unloading volumetric curves，the characteristic strength and deformational modulus evolvement process are obtained based on damage-controlled testing. The results show that the deformation modulus，crack-damage strength and peak strength are all decreasing with damage growing；however，once the damage reach to a certain degree，the damage strength promptly decrease earlier than peak strength，and the peak strength keeping on increasing with damage growing and then decreasing gradually. By further analysis，the internal friction angle and cohesion evolvement law during failure process are discovered，that is，cohesion decreases rapidly with damage growing and reach to residual；but internal friction angle experiences increasing firstly then decreasing slowly，among which the increasing period happens to the moment of most cohesion loss. All the experimental results play a significantly theoretic role in discovering the failure mechanism of brittle rock.
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Received: 14 April 2012
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2012, Vol. 31 
