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Abstract Laboratory results can hardly reflect the rheological properties of engineering rock mass because of the size-effect of samples and the difference between test conditions and work state of engineering rock mass；so in-situ creep tests were carried out in some important hydropower projects；and the in-situ plate-loading creep test is applied more often. But in the test method，there exist some shortages，so it is suggested that the generalized five-parameter Kelvin model can be accepted to describe the rheological properties of rock mass；and the single-stage loading manner with load level being consistent with engineering load is suggested. The creep deformation equation based on generalized five- parameter Kelvin model of rock mass under plate-load is deduced；and it is found that the results agree with elastic deformation equation when t = 0 or t→∞. Finally，test examples，of which creep model and its parameters are inversed using nonlinear least squares curve fitting method，are given to demonstrate that the magnitude of the correlation between generalized five-parameter Kelvin model and test curves is superior to that of generalized three-parameter Kelvin model.
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Received: 02 February 2009
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