When drilling is executed in the deep rock mass

rock is mainly subjected to loads with medium and low strain rates. However the medium and high strain rates damage constitutive model is still used instead

which doesn’t adapt to the real situation. The dynamic characteristics of rock under medium and low strain rates are analyzed from engineering background and practical experiments. A parallel model of rock

which is made up of Maxwell element

Bingham element and damage element

is proposed. The damage parameter based on degradation of pore and fissure is introduced with Laplace transformation. A new dynamic damage constitutive model of rock is derived. The proposed model is used to fit the stress-strain curves of argillaceous sandstone and granite at strain rates of 87 s-1

382 s-1 and 673 s-1. By comparing fitting results with the experimental data and literature results

it is shown that the proposed model is suitable for the behavior of rock under medium and low strain rates. With analyzing the fitting parameters

the proposed model can actively adapt to medium and low strain rates. The variations of constitutive curves and damage parameters are in agreement with the practical situation.