Abstract: Weakly cemented soft rock show significant creep characteristics under water rich condition, which seriously affect the safety of mining and slope engineering. A series of multi-stage loading creep tests was carried out by using GDS HPTAS creep triaxial apparatus to investigate the creep behavior of the weakly cemented soft rock with different moisture contents. Creep deformation, creep rate and failure mode were analyzed. Thus, the long-term strength and its variation were determined according to the inflection point of the creep rate vs. stress curves of the weakly cemented soft rock with different moisture contents. Based on the test results and fractional calculus theory, a new four-element fractional-order creep model was proposed by using Abel clay pot instead of Kelvin clay pot element, and the plastic element was applied instead of the elastic element, the three-stage creep behavior of weakly cemented soft rock was described. The Trust-Region method was adopted to determine the model parameters of the four-element fractional-order creep model. The relationship between the model parameters, moisture content and loading stress was analyzed by the multivariate nonlinear regression method. The effect of moisture content and loading conditions on the creep behavior of the weakly cemented soft rock was also discussed. From the perspective of comparative analysis, the numerical results calculated by the four-element fractional-order creep model are in good agreement with the test data, the proposed model can accurately simulate the whole creep behavior of weakly cemented soft rock.

Key words: weakly cemented soft rock, fractional-order calculus, creep model, long term strength, GDS HPTAS triaxial apparatus