Research On Damage And Failure Characteristics Of Rock Under Freeze-thaw And Loading Considering The Residual Strength

With the development of economic construction,the exploitation of the Geotechnical engineering quantity and scale in cold region,the freeze-thaw rocks have become a key scientific issue that must be resolved for freeze-thaw disaster prevention.The damage mechanism and failure condition of rock under the freeze-thaw are further researched,considering that the engineering construction safety production is of practical engineering significance.The damage model and strength criterion of rock under freeze-thaw and loading are studied in this paper by combining the macroscopic-mesoscopic methods with statistical methods.Based on the Weibull statistical distribution and Drucker-Prager criterion,a damage model which can better reflect the deformation characteristics of rock residual section is established with the assuming that the loaded rock is divided into a damaged and undamaged part of the material,and the damage can bear the force of the residual strength.The theoretical expression of the model parameters is obtained by using the peak point method,and its physical meaning is analyzed.In view of the rock damage model established by the commonly used correction factor,the applicability of the deformation characteristics of the rock residual section is discussed and analyzed from the mathematical form.Considering the influence of freezing and thawing factors and load factors on the rock,the rock damage model under the combined action of freeze-thaw cycles and load is established based on the concept of total damage variable.The variation law of damage variable and total damage evolution rate under different confining pressure and different freeze-thaw cycles are analyzed and discussed.The number of freeze-thaw cycles is increasing with the degree of damage to the rock increasing,the macroscopic mechanical properties deteriorating,the compressive strength and the residual strength decreasing,and the failure model tending to ductile failure;The confining pressure is increasing,with the damage degree of rock damage decreasing,compressive strength and residual strength increasing,brittle characteristics gradually disappearing,and the ductility characteristics gradually becoming apparent.By analyzing the geometrical characteristics of the stress-strain curve of the rock at the peak point,the rock strength criterion considering the freeze-thaw effect is established by using the multivariate function.The criterion can be used to characterize the relationship between the internal stress parameters of the rock in the limit state and the curve properties of the strength Mohr envelope in different freeze-thaw cycles.When the number of freeze-thaw cycles increases,the strength of the Mohr envelope curve is more obvious,indicating that the criterion is suitable for the determination of the strength of the frozen rock,and then the damage threshold is reestablished to establish a new type of freeze-Damage model.Compared with the experimental data,the results show that the modified freeze-thaw load model can not better reflect the Plastic yield stage of rock,but it is still in good agreement with the test curve in the posterior segment and the residual section.