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Abstract The stress relaxation tests of dry and saturated silty mudstone under triaxial compression were performed with the servo-controlled rheology testing machine RLJW–2000. The effects of water on the magnitude，the level and the time of the total relaxation and the average relaxation rate were analyzed according to the experimental results. A damage variable was proposed to consider the weakening of rock parameters. A new nonlinear damage model was established by introducing the damage variable into Hooke-Kelvin model. The Levenberg-Marquardt algorithm was adopted to identify the model parameters of dry and saturated rock. The effects of water on the parameters of the nonlinear damage model were studied according to the results of identification. For water saturated rock，the total relaxation decreases but the degree and the time of the total relaxation increase after stress relaxation. The effects of water on the magnitude and level of relaxation are reduced with time increasing during the period of stress relaxation. The average rate of relaxation and the rate of relaxation at different time decrease due to the effect of water，and the effect of water on the reduction of relaxation rate of rock increases with the increasing of time during the stress relaxation. The viscosity of rock was affected significantly by water and the instantaneous elastic and viscoelastic properties of rock are less affected. The damage of rock due to stress relaxation is related to these factors，the strain level，the time and the occurrence of water. The nonlinear damage model effectively reflect the deterioration of rock properties induced by these factors. Overall，water has significant effects on the properties of stress relaxation of silty mudstone，which should not be ignored in design and construction of major projects.
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Received: 08 April 2014
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2015, Vol. 34 
