Study On Multi-scale Evolution Of Loess Structure Under Compression And Shear

Natural loess has obvious structural characteristics,and structural evolution is the internal cause of loess engineering disasters.With the implementation of the national strategy of"promoting the development of the western region in the new era and forming a new pattern",a series of infrastructure construction with large capacity and high standards will usher in a new round of development opportunities.However,due to the special sensitivity of loess to water and force,a large number of loess engineering disasters need to be solved.Therefore,it is of great theoretical significance to study the multi-scale whole process evolution law of loess structure under compression and shear.Based on the theory of comprehensive structural potential,the structural parameters and their evolution rules of loess arc systematically analyzed through confined compression test,conventional triaxial test,true triaxial test and uniaxial compression test.The internal correlation of various structural parameters under different test boundaries is explored.Combined with microstructure test,the structural evolution rules of loess under compression and shear are revealed in multi-scale.Based on the critical state theory,the yield and strength characteristics of loess with structural evolution are studied.The main achievements of this thesis are as follows:1)Through a series of structural tests on loess,the rationality and evolution law of various structural parameters are verified and analyzed.Politics has been clear about the degree index and structural parameters of the cone penetration test to measure structural reasons and characteristics of undisturbed loess initial state;Pointed out based on the comprehensive structure potential structural parameters are thought to establish a series of process on the external performance such as sensitivity,decay curve,but reveals the structural evolution of the essence for the formation of the destruction of the primary structure and secondary structure.2)Through the micro way such as SEM scanning test,mercury injection test,the conventional triaxial consolidation shear process corresponding microscopic loess particles and pores,the average diameter change rule.Points out that the coupling effect between the loess is are connected by a recoverable action(such as the matrix suction,electric double layer repulsion,etc.)and unrecoverable coupling effect(such as cementing material effects)of two parts.3)By theoretical derivation and experimental verification,and points out that the axial stress and structural stress of structural parameters can joint reaction ball pressure loss and the shear stress shear loss function of structural stress ratio and pressure loss of the structural parameters of the reaction is shear damage of contribution to the structural damping ratio;After structural parameters and the strain stress structural parameters,can reflect in a stripe,reveals the structural damping law that have homogeneity;Based on comprehensive structure potential reflects the various structural parameters of the date of the loess structural decline rule of one side.4)Normal consolidation line is obtained by confining compression test and then come to e-ln(p)of the plane structure such as line;P-q is obtained by triaxial shear test of consolidation line parallel plane structures,etc.