Shear creep characteristics and constitutive model of limestone

The characters of limestone in weak interlayer of a high rocky slope in Xuzhou, China, are studied by shear static test and shear creep test. The results show that limestone specimens have attenuation creep properties and constant rate creep properties, almost have no accelerated creep properties. The exponential type empirical formula is selected to fit creep grading curves by polynomial regression analysis method, and the square sums of the fitting results residual are in the order of 10(-7). Then grade creep curves at every shear loads are set up. Combining creep rate-time curve, the creep properties of limestone are analyzed. As the physical meaning of component model is clearer, the Poytin-Thomson model is set up. Through the least square method, the optimal parameters of Poytin-Thomson model are obtained, and the sums of squared residuals belong to 10(-3) order of magnitude, which can meet the accuracy requirements of engineering calculation. So the Poytin-Thomson model can reflect the shear creep characteristics of limestone very well. (C) 2016 Published by Elsevier B.V. on behalf of China University of Mining & Technology.