Abstract The deformation of rock mass takes on time-dependent effect after its excavation；and the instaneous mechanical and rheological mechanical responses of rock mass vary greatly in some degree. At present，the research on this rheological behaviour is mostly based on loading conceptual rock rheological test. However，researches on the rheological property under unloading stress path are seldom taken into account. Thus，the results sometimes cannot coincide with the practical mechanical process. The fresh shale sample in underground powerhouse of Pengshui Hydropower Station are taken to carry out unloading rheological test under the stress conditions of constant axial stress and gradually unloading lateral stress so as to preliminarily study its triaxial unloading rheological property. Experimental research reveals that the axial and lateral creep curves of shale specimens behave the attenuation creep stage under relatively low stress state. The rheological constitutive equation is obtained by means of parameters regression of H-K three-component model. Research reveals that the H-K three-component model can well present the unloading rheological behaviour under this stress state.
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Received: 15 September 2007
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