Analysis Of Physical Mechanics Characteristics Of High Moisture Content Loess Under The Freeze-thaw Condition

Loess in China, widely distributed in the northwest and north China, are in seasonal frozen soil areas. Loess structures of the seasonal frozen soil areas in its construction and operation, will be inevitably subjected to freezing and thawing cycles. Freeze-thaw cycles will greatly change the original structure of soil, resulting in physical mechanics properties of loess deteriorated. Freezing and thawing is one of the important reasons for the seasonal frozen soil engineering properties of loess structure deteriorated. At present,while the impact of freezing and thawing on the physical nature of the loess have been studied more deeply, the impact of freezing and thawing on the mechanical properties of loess has not got access to the systematic research, nor have any comprehensive laws been proposed, pending further study.This paper, on the basis of researching No.1 loess highway tunnel in Shanxi YangQu,taking YangQu high moisture content of unsaturated loess as the research subject, first of all, makes a study of the physical properties of loess, analysing the particle gradation composition of this region, moisture content and liquid plastic limit parameters and range.Then the paper makes further study of the different moisture content under the condition of the mechanical characteristics of undisturbed loess and loess, discussing the factors that affect its mechanical properties and laws; different freeze-thaw cycles and the different moisture content under different freezing temperature YangQu of undisturbed loess and loess unconfined uniaxial compressive strength and direct shear have been gone through systematically experimental study. After that, consolidation, get the same-to restore the relationships between the loess, freeze-thaw conditions and moisture content of the three are reasonably demonstrated; Comprehensive analysis of YangQu loess under different freezing and thawing cycle of stress-strain curve and shear index(cohesive force and Angle of internal friction) and the variation regularity of deformation of compression feature; In addition,the systematically experimental research and a profound analysis of the results haven been made on the structureand the structural intensity of YangQu high moisture content loess.The research results show that: ?YangQu loess under freezing and thawing condition produces frost heave force-induced change of loess microstructure, the mechanical properties of macroscopic changes in loess, which matches the change of the physical mechanics properties of loess under freezing and thawing; ? with an increase in the times of freeze-thaw cycles and decrease in freezing temperatures, loess unconfined compressive strength shows different floating decline, while undisturbed loess fall of float generally becomes higher than remodeling loess;?undisturbed-remodeling loess cohesion are decreased as the initial moisture content increases, which reduces the magnitude more obviously, apparent friction angle variation does not appear under different conditions of freezing and thawing;?with the degree of deterioration increasing, remodeling loess compression factor varying float increases;?the application reflects the structure and the structural strength of the two initial structural parameters of loess, on the basis of freezing and thawing, deeply understanding high moisture content loess characterisitics of water sensitivity, strength and deformation.