Damage And Failure Mechanism Of Argillaceous Dolomite After Freeze-thaw Cycles Based On DIC

Argillaceous dolomite is widely distributed in Guizhou Province,which is a kind of complex medium in slope engineering,underground chamber,tunnel,as well as in dam foundation.The effect of freeze-thaw cycles will induce a series of rock mass engineering disaster such as frost heaving and thaw settlement,collapse,landslide and debris flow.The freeze-thaw cycle often leads to deterioration of argillaceous dolomite strength,and the deformation increases,which must be considered in the design and construction of rock engineering,in addition it will affect the normal operation of rock engineering after putting into use.With the advancement of the western development strategy,massive freeze-thaw rock engineering has become a reality to be solved,so the research for the frozen-thaw damage failure mechanism of the argillaceous dolomite has practical value of for rock engineering in Guizhou province.Digital image correlation（referred to as DIC）is a representative optical measurement method which is developed in the recent years,and its theory and application are gradually mature.At present,the method can be used for visual and quantitative analysis of the test object.With the help of DIC technology,the deformation process of the whole deformation field can be measured,Such as inhomogeneous deformation field and crack propagation.ThiS paper use 3D-DIC to study the deformation field and failure process of argillaceous dolomite after freezing and thawing cycle,during uniaxial compression test and Brazil disk split test,and further more give a quantitative analysis of deformation failure mechanism.Based on the analysis of cylinder uniaxial test results,this paper take the tensile strain ε_x in the horizontal direction,compressive strain ε_y in vertical loading direction,and shear strain ε_xy as the damage mechanics parameters.During the splitting test in Brazil disc,this paper take the tensile strain ε_x in the horizontal direction,compressive strain ε_y in vertical loading direction as damage mechanics parameters.The surface field data of the two tests were further analyzed.statistical results shows that the strain average values of different mechanical parameterS of the two tests surface field increase with the pressure load,and there are significant differences in different stages;It is easy to see that the damage evolution and crack propagation of the rock is determined with large strain points,such as 5% of the larger strain in the average value of the strain localization and crack initiation stage shows a rapid nonlinear growth,while the most of the remaining strain point of steady growth.Through the analysis of the statistical data obtained at every moment,an updated damage evolution of two factor characterization methods of modified argillaceous dolomite is preSented.The horizontal strain at each moment was taken as the key parameter of damage evolution,and then statistics and analysis the experimental data.Damage accumulation factor D1 and damage localization factor D2 of argillaceous dolomite is presented to describe the extent of damage and localization of damage and the curves of double factor versus are given.Damage evolution two factor is applied to measure the damage evolution of uniaxial compression test and Brazil disk split test after freeze-thaw,the experimental results show that the damage localization degree decreases gradually and the whole strain is uniform,the localization factor approaches 1 at the beginning of elastic phase.The degree of localization increases gradually with the increase of load and the macroscopic crack was formed at the intersection of the double factor curve,and with the increase of freezing thawing times,the localization factor reaching 1 and the crossing time of the double factor curve becomes more and more early.