CT Identification And Evolution Analysis Of Muddy Interlayer Damage

The silted intercalation is a common type among the weak intercalated layers with poor physical-mechanical properties and low strengths.Specifically,the silted intercalation acts as the control one in slope stability because it is an important factor leading to the slope failure.Usually,for bedding slope,the failure occurred in silted intercalations,is the results for the concentrated embodiment of its internal micro-meso damages.When affected by the external factors,such as rainfall and artificial excavation,the internal micro-meso structures in silted intercalations change constantly,and the damages are produced and developed with it.Finally,this phenomenon evolves to the degradation in macroscopic physical-mechanical properties,which brings about the failure of silted intercalations,to create conditions for the slope failure further.At present,the researches of the silted intercalation focus on the macroscopic mechanical properties,but studies regarding to the internal meso-damage evolution when applied loading in silted intercalations were paid little attention.In this paper,the silted intercalation sample which is from a backwall in Xiaobangshang landslide is taken as the research object.Through the computed tomography(CT),uniaxial compression tests and triaxial shear tests for silted intercalations are performed to identify the meso-damages,and establish the damage evolution equations,along with the constitutive relations.In addition,the impacts of the sample strength on suction are dealt with.The main contents and methods in this paper are as follows.(1)Based on the CT in the process of loading for silted intercalations,scanning images and data have been acquired.Through the images and data,the damaging process with the increasing loads and evolution law have been obtained,respectively.(2)By the suction in the value of 200kPa application to the sample,specifically,the net ambient pressure have been controlled as 50kPa,100kPa and 200kPa,the curve of deviatoric stress over axial strain under different ambient pressures has been obtained,and has been contrast with the results with no matrix suction imposing.It is found that the suction has a great influence on the strength of the interlayer.(3)By the analyses for the uniaxial compression tests and triaxial shear tests,the curve of deformation modulus over axial strain has been plotted.Then the deviatoric stress(strain)corresponds to peak value of the deformation modulus has been considered as the threshold of damaging stress(strain)of silted intercalations.And the damage variable has been defined by the deformation modulus corresponds to the threshold.The influence of different confining pressure and suction on the damage evolution of mud interlayer was analyzed.Moreover,combined with the axial strain,the damage evolution equations and constitutive relations have been set up.In this paper,by the uniaxial compression tests and triaxial shear tests for silted intercalations based on CT,combined with the damage accumulation theory,the meso-damages have been identified and analyzed.And the deformation modulus-based damage variable has been defined under circumstance of only the axial damage has been considered.The relationship between the damage variable and the axial strain was analyzed,then the damage evolution equations and constitutive relations have been obtained.Furthermore,the mechanical properties and the damage evolution rule of silted intercalations under different confining pressures when applied matric suctions have been discussed preliminary.