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Experimental Study of Reconstituted Clay and Intact Clay Under Principal Stress Rotation

Author: ZhengHongZuo
Tutor: WenXiaoGui；ZhouJian
School: Zhejiang University
Course: Geotechnical Engineering
Keywords: Principal stress rotation Undisturbed clay Remodeling clay Experimental study
CLC: TU411.99
Type: Master's thesis
Year: 2011
Downloads: 117
Quote: 0
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Abstract

Transportation, wave loads of soil will occur in the principal stress rotation, rotation of principal stress stress paths with conventional triaxial test path, the corresponding response of the soil there are significant differences. In this paper, on the basis of previous studies, with the Zhejiang University hollow cylinder torsional shear apparatus (ZJU-HCA) Hangzhou undisturbed and remolded clay comparative test research. Content and conclusions of this study are as follows: First, set two intact soft clay sample default the same stress path, compared to the same stress path stress-strain curve, found that: (1) Actual test constant shear stress or principal stress axes deflection angle alpha stress path can be effectively implemented, the amplitude of the fluctuations in the data is very small, a high degree of accuracy; (2) under the same stress path, two sets of specimens axial stress-strain and hoop stress-strain curve close torsional shear strain and circumferential strain amplitude is small, the maximum difference is only 0.03%; (3) the sample strain component changes with the corresponding stress component changes consistent strain component change is reasonable. These results and reliable performance of the instrument, test repeatability, high comparable test results are accurate. Undisturbed clay of the Hangzhou the consolidated undrained directional shear and pure principal stress axes rotation test, test, maintain the average principal stress p = 150kPa and principal stress coefficient b = 0.5, explore the initial shear stress on the pure principal stress axes rotation strain components, generalized shear strain shear modulus and pore pressure carried out. The results showed that: (1) radial strain, circumferential strain, axial strain and torsional shear strain variation characteristics and the size of the initial shear stress on the strain components carried out consistent with the previous research results; (2) soil subjected to pre- principal stress rotation so that the latter generated by the rotation of principal stress axes generalized shear strain increased significantly, and the shear modulus decreases; (3) According to the theory of double yield surface derived pure principal stress axes rotation, the pore pressure coefficient, found the hole pressure coefficient of soil elastic bulk modulus of deformation and volume yield surface function, combined with pore pressure linear fitting results found, initial shear stress below the peak shear stress, volumetric yield surface function from the rotation of principal stress affected; when the initial close to the peak shear stress, shear stress and the principal stress rotation sample pore pressure rise rate is relatively high. The paper focuses on the Hangzhou reshaping the clay to carry out the pore pressure and strength characteristics the consolidated undrained directional shear tests, participate in the development of indoor remodeling clay the vacuum suction consolidation of tube, the different initial stress state to reshape the clay stress strain the impact. The results show that: (1) remodeling clay axial stress-strain and hoop stress-strain change mode is controlled by the deflection angle of the principal stress axes, axial and circumferential strain to the principal stress axes deflection angle equal to 45 ° is bounded to the positive negative changes; contrast, the radial stress and strain and torsional shear stress strain change mode by the deflection angle of the principal stress axes, radial strain and torsional shear strain does not appear positive and negative to change characteristics; (2) the main stress coefficient reshape the clay pore pressure and intensity changes have a certain impact, but the principal stress axes deflection angle of the pore water pressure to carry out the mode and intensity change; (3) study found that generalized shear stress peak, or stable hole pressure as discriminant the failure criterion remodeling clay as inappropriate by generalized shear strain on the soil reaches a predetermined degree of play of the soil strength, it is recommended to take a generalized shear strain is equal to 8% of the strength as to reshape the breaking strength of the clay. In order to further deepen the principal stress axes rotation under the clay primary and secondary anisotropy understanding of the relationship, similar stress path the undisturbed clay remodeling clay test results were compared, the results showed that: (1) secondary anisotropic impact the clay stress and strain and pore pressure to carry out mode, the mode is determined by the axial stress and strain, the hoop stress-strain and pore pressure to carry out secondary anisotropic control; contrast, secondary anisotropy of the radial stress strain, torsional shear stress-strain Models of generalized shear stress and strain; (2) native anisotropy of the stress components to carry out the scope and magnitude of intensity changes have a significant effect, undisturbed clay stress amplitude changes in the amount of change The scope and magnitude of significantly higher than reshape the clay, the changes in the intensity of the undisturbed clay by native anisotropy effects, but little change to reshape the normalized intensity of the clay on the different principal stress axes deflection angle. The paper also reshape the sand under similar stress path and remodeling clay test results were compared to study similar to the response of different soil stress paths, the results show that: (1) similar stress paths remodeling sand and remodeling clay hole pressure to carry out significant difference in the mode the phase transition point, sand, clay; (2) remodeling of sand and reshape the clay stress-strain curve there is a big difference, the presence of sand strain softening and hardening clay only showed strain hardening characteristics.

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CLC: > Industrial Technology > Building Science > Soil mechanics,foundation engineering > Soil Test > Laboratory tests (indoor soil test ) > Other soil test
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