Study On Structure Characteristics And Dynamic Behavior Of Loess

Loess is a kind of typical structural soil, its special structure and special sensitivity to water effect on the characteristics of engineering mechanics of loess, this is also the special aspect of the study on dynamic behavior of loess. In this paper, the structure characteristics and the dynamic behavior of loess are studied by the static and dynamic tests of intact loess, man-made loss and man-made cement structural loess in laboratory.Above all, based on analyzing the structure characteristics and its developing mechanism, the cement structural loess is made in laboratory, and the structure characteristics of intact loess and man-made cement structural loess are studied with confined compression test and triaxial compression test. The research results show that Compression curves of intact loess and man-made cement structural loess are very approached to each other on the condition of some certain moisture content and cement content, so the method of using cement as bonding material to make man-made cement structural loess is available. The structural strength of man-made cement structural loess can be changed according to moisture content and cement content, and its structure characteristics can also be changed by adjusting moisture and cement content.The structural strength of loess reflects its structure characteristics. The methods of quantitative analysis of structural strength of loess are put forward, and effects of soil moisture upon structural strength of loess are also quantitatively analyzed in this paper. The strength of loess is formed by structural strength and compaction strength, and structural strength can be expressed by the difference of stress between structural loess and man-madeloess. The structural strength of loess can be quantitatively analyzed by different test in laboratory. The curve of structural strength exerting process reflects that structural strength changes from strain. The moisture has a remarkable effect on structural strength of loess.In this paper, some aspects such as the behavior of pore pressure of unsaturated loess, the dynamic constitutive relationship and the characteristics of the dynamic modulus, dynamic strength and dynamic damping ratio are studied with the dynamic torsional shear test of loess. The pore air pressure gradually goes up with the developing of axial strain in the process of the dynamic torsional shear test of loess, but the pore water pressure hold the line or goes up a little in the last. The stress-strain dynamic constitutive relationship of intact loess and man-made loess show the hyperbolic model. There are some remarkable differences of strength and strain between unsaturated loess and saturated loess. The effects of water content, consolidation pressure and consolidation pressure ratio on the dynamic characteristics of loess are analyzed. In the last of this paper, the formulas for calculating effective stress of unsaturated loess are also discussed. The relativity of strength index between static and dynamic test of loess is analyzed, and some experience formulas of ascertaining dynamic strength index according static strength index are advanced.