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| CHARACTERISTICS OF PORE WATER PRESSURE OF INTACT SOFT CLAY UNDER ROTATION OF PRINCIPAL STRESS AXES AND INTERMEDIATE PRINCIPAL STRESS COEFFICIENT(b) OF 0.5 |
(Key Laboratory of Soft Soils and Geoenvironmental Engineering，Ministry of Education，Zhejiang University，
Hangzhou，Zhejiang 310058，China) |
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Abstract Consolidated-undrained shear tests of rotation of principal stress axes are carried out on Hangzhou intact soft clay with hollow cylinder torsion shear apparatus(ZJU-HCA). The influence of shear stress change，initial shear stress level and both positive and inverse rotation of principal stress axes on characteristics of pore water pressure development clay are discussed. In the tests，the mean principal stress is kept constant and the intermediate principal stress coefficient is set to 0.5. The test results show that the pore water pressure in fixed shear period is mainly controlled by shear stress. The pore water pressure coefficient is acquired by double yield surface theory，which is combined with linear fitting results of pore water pressure to reveal that the volume yield surface function is not affected by the rotation of principal stress axes when initial shear stress is below the peak shear stress. If the initial shear stress is close to the peak shear stress，a relatively high velocity of pore water pressure is generated at the beginning of rotation，but later pore water pressure decreases. The corresponding velocity of pore water pressure in the rotation process of pure principal stress axes is mainly dominated by initial shear stress. The pore water pressure under positive rotation of principal stress axes is smaller than that under inverse rotation. The influence of inverse rotation of principal stress axes on pore water pressure is larger than that of positive rotation through the whole shearing process.
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Received: 12 May 2010
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2010, Vol. 29 
