Studies On Tensile Mechanical Properties And Structural Parameters Of The Loess

For a long time,most studies on the mechanical properties and the structure of loess focused on its compression-shear properties but ignored the tensile properties.However,the tensile properties and compression-shear properties of soil are two important aspects to reflect structure and both of them can not be neglected.Previous studies on tensile structure mainly took the way transforming the compression-shear structural parameter to the tensile structural parameter through mathematical transformation.But it can not get the real tensile structural parameter by this way.The only way to get the real tensile structural parameter is based on the research on the tensile properties of the soil.The tensile test device was improved in this paper.Through the tensile tests of the structural loess,the tensile stress-strain relation of the structural loess has been studied and the tensile structural parameters of structural loess have been established.Combined with the compression-shear structural parameters,the joint strength of the structural loess considering the complete structure has been discussed.And at last,the trend was applied to the stability calculation of structural loess slope by computing corresponding program to analyze the stability of real loess slop.The results are as follows:(1)Comparing the advantages and disadvantages of various tensile testing apparatus,we improved the soil beam tensile testing device based on electric control loading and made it to be a uniaxial tensile test device that can accurately and efficiently measure the tensile stress-strain curve.At the same time,the related ancillary equipments are developed and tested.(2)By uniaxial tensile test,the stress-strain relationship and tensile strength of structural loess came out.The relationships between tensile strength and moisture,tensile modulus and strain,initial tensile modulus and moisture,initial tensile modulus and tensile strength have been researched.And we discussed the differences of the tensile properties of the soil samples reshaped by different ways.(3)On the bases of comparison of the tensile strength of intact loess,conventional reshaped loess and maximum dry density-optimum moisture loess,the tensile strength structural parameter has been established considering structural damage,particle component and the degree of compaction.And the relationship between the tensile strength structural parameter and corresponding mechanical index has been studied.(4)On the bases of comparison of the tensile modulus of intact loess,reshaped loess and saturated loess,the tensile modulus structural parameter has been established within the framework of the comprehensive structural potential.And the relationship between the tensile strength modulus parameter and corresponding mechanical index has been studied.Then,the joint strength of the structural loess considering the complete structure has been discussed combining the compression-shear structural parameter(stress ratio structural parameter).(5)Introducing the joint strength of the structural loess considering the complete structure to the finite element analysis of slope,we programmed corresponding procedure,carried out an actual example and discussed influences on the slope stability analysis in the joint strength theory considering the tensile structure or not.