Experimental Study on Creep Characteristics and Damage Model for Carbonaceous Slate After Freezing and Thawing
In order to reveal the creep mechanics of carbonaceous slate after freezing and thawing,the Zhuokeji tunnel on Wenchuan-Ma'erkang expressway is taken as the study object.Triaxial compression creep tests are conducted with different freeze-thaw cycles.Assuming that the time-dependent damage of rocks under load follows a Weibull probability density distribution,and the load damage variable is defined.Based on the phenomenological damage mechanics theory,the freeze-thaw damage variable is defined,considering the coupling effect of freeze-thaw and stress,and constructing the total damage variables of freeze-thaw and load.Based on the creep behavior of carbonaceous slate,the H-H | N-N | S creep model structure is determined,based on which the damage evolution is carried out.A new creep damage model reflecting the coupling of freeze-thaw and stress is obtained,which is extended to a three-dimensional stress state.A method for solving model parameters is provided,and the damage evolution rule is analyzed.The established model is used to identify the creep data of carbonaceous slate.A traditional model is introduced for comparison,and the simulation comparison curve is analyzed to verify the feasibility and rationality of the new model.The result shows that(1)the creep test curve of carbonaceous slate shows a stepped shape,and the axial strain increases with time;(2)as the freeze-thaw effect increases,the long-term strength decreases,and the freeze-thaw cycle may reduce the difficulty of rock creep failure;(3)the new model has a good simulation effect on the creep behavior of carbonaceous slate with an average R2 of 0.987 8,proving the feasibility of the new model in describing the creep characteristics of carbonaceous slate after freezing and thawing.The strengthening of freeze-thaw action accelerates the development of damage to the internal structure of carbonaceous slate,and promotes the creep failure of the rock to a certain extent.
tunnel engineeringcreep characteristicsdamage modelcarbonaceous slatefreezing and thawingdamage variable
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