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Research on Creep Characteristics of Expansive Soil

Author: FanZhiQiang
Tutor: XiaoHongBin
School: Hunan University
Course: Geotechnical Engineering
Keywords: Expansive soils Creep Nonlinear Burgers body rheology model
CLC: TU443
Type: Master's thesis
Year: 2009
Downloads: 70
Quote: 2
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Abstract


Based on the current situation of the domestic and foreign soil creep, on the basis of comprehensive analysis, combined with the general project funding of the Science and Technology Department of Hunan Province, and the Key Project of Hunan Provincial Education Department and Hunan Province Natural Science Foundation-funded research projects, this paper carried out Nanning expansive soil creep properties. Through laboratory experiments, theoretical analysis and numerical analysis method of combining research, mainly made the following aspects of the conclusions and innovative research: 1) for the stage loading, with or without pre-pressure and control different loading than under conditions unsaturated expansive soils the consolidation test studies have shown that: preload, when the loading ratio is equal to 1 and the loading ratio equal to 2, the void ratio and time logarithmic curve is different, the former showed a good linear relationship; the porosity of the latter than the logarithmic curve with time as the load increases, from the approximate straight line into a curve; preload, when the loading ratio is equal to 1, at a pressure of less than 200 kPa and the pressure is greater than 200 kPa , the void ratio and time logarithmic curve showed a different trend; according to the results of the consolidation test fitting out pre-pressure of 200 kPa and preload Δε-t-lg p constitutive equation. 2) as the research object unsaturated Nanning expansive soils, consider having loaded stage loading, consider preloading load test program. Consider different moisture content, stage loading different loading ratio, density expansive soil rheological The results show that: 1 load, the grading load test and consider preloading load compression test strain - time curves have the same trend: small stresses, soil showed linear deformation, greater stress soil deformation curve can be fitted to the logarithmic form; 2 compression creep tests were loaded, soil instantaneous strain and load between a quadratic fit higher degree; eliminate soil by preloading processing post-construction settlement is favorable; 4 to strain the most influential factor is the moisture content, followed the density from the creep test curves of unsaturated expansive soils with nonlinear deformation, and finally for the vertical stress; characteristics. 3) study by the modified direct shear creep tester Nanning Unsaturated Expansive soil different vertical pressure and shear strain under different moisture - time curve, the following results: 1 when the stress level is lower than the yield limit, Nanning non- unsaturated expansive soil performance attenuation creep; unsaturated Nanning expansive soils generally have significant nonlinear rheological properties when the stress level is higher than the yield limit, nonlinear performance of development gradually with the increase of stress and time intensified; isokinetic creep stage, the strain - time curves can be fitted to the synthesis of linear functional form, fit a high degree; accelerating creep stage, some strain - time curves can be fitted synthetic quadratic function; 3 The higher the moisture content, the more obvious the rheological characteristics of the soil. With the increase of moisture content, shear rheological properties of the soil from the linear rheological into nonlinear rheology; 4 indoor shear creep test, Nanning Unsaturated Expansive Soils time curve can be drawn. 4) Nanning Unsaturated Expansive soil compression creep tests under conditions of normal work stress viscoelastic model of comparative study and shear creep test yield viscoelastic model under extreme conditions: in compression creep test, the normal stress conditions, both were loaded or grading load, Nanning Unsaturated Expansive soil creep curve fitting Burgers body model can be applied, and obtained constitutive equations and creep equation; in shear cut creep test, the shear stress is less than the yield of soil samples can limit the use of the Burgers body model fitting and obtained constitutive equations and creep equation. The expansive soil rheological process its consolidation is always coupling effect.

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CLC: > Industrial Technology > Building Science > Soil mechanics,foundation engineering > Various types of soil and foundation > Expansive soil and foundation
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