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Abstract The rock material is a kind of non-homogeneous material and there are a large number of defects such as fissures，voids，interfaces in the broken rock. Its micro units damage more randomness under the loads. Starting from micro units strength are random distribution on the basis of damage theory，a method for measuring microcosmic element strength of rock is presented with consideration of damage threshold. Assuming the micro units strength of broken rock obey Weibull distribution，combined with the SMP criterion，which considers the intermediate principal stress，the statistical damage softening constitutive model is built. And the model parameters m and F0 are computed using some methods. Through the calculation results of two kinds of broken rock in Xiaoguanzhuang indicate that：the predicted stress-strain curves under different confining pressures agree well with the test data，and it can reflect not only the influence of damage threshold but also more desirable in the lower confining pressures. At the same time，this model can reflect the characteristic that the peak strength increases and ductility increases with the confining pressure increase，which further shows that the applicability of the model and a strong application value.
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Received: 07 September 2012
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2013, Vol. 32 
