主应力轴纯旋转条件下原状黏土变形特性研究

发布时间：2018-12-25 08:18

【摘要】：采用空心圆柱扭剪仪对原状软黏土进行了不排水条件下的主应力轴纯旋转试验,即主应力轴旋转过程中平均主应力、剪应力和中主应力系数都保持不变。重点研究了中主应力系数对原状软黏土在主应力轴纯旋转条件下的孔压和变形特性的影响,基于试验结果对主应力轴纯旋转的影响机理进行了分析。试验结果表明:即使3个主应力的值都保持不变,原状黏土的孔压和应变也会随着主应力方向的旋转而累积,经历主应力轴的旋转后土体刚度减小;主应力轴连续旋转时主应变增量方向与主应力方向存在显著的非共轴现象;中主应力系数对主应力轴旋转条件下孔压和应变的开展以及刚度衰减有显著的影响,而对非共轴特性的影响较小。电镜扫描结果表明经历主应力轴旋转后黏土颗粒破碎聚集成较大的团粒,大孔隙显著减少,颗粒和孔隙分布趋于均匀,主应力轴旋转的影响机理可以归结为主应力轴旋转对土体微观结构的扰动和破坏。
[Abstract]:The pure rotation test of principal stress axis in undrained soft clay was carried out by hollow cylindrical torsional shear apparatus. That is to say, the average principal stress, shear stress and mid-principal stress coefficient remained unchanged during the rotation of principal stress axis. The effect of medium principal stress coefficient on pore pressure and deformation characteristics of undisturbed soft clay under pure rotation of principal stress axis is studied. Based on the experimental results, the influence mechanism of pure rotation of principal stress axis is analyzed. The experimental results show that even if the values of the three principal stresses remain unchanged, the pore pressure and strain of the undisturbed clay will accumulate with the rotation of the principal stress direction, and the soil stiffness will decrease after the rotation of the principal stress axis. When the principal stress axis rotates continuously, the increment direction of the principal strain and the direction of the principal stress have obvious non-coaxial phenomena. The coefficient of middle principal stress has a significant effect on the development of pore pressure and strain and stiffness attenuation under the rotating condition of principal stress axis, but has little effect on the non-coaxial characteristic. The scanning electron microscope results show that after the rotation of the principal stress axis, the clay particles are broken and gathered into larger aggregates, the macropores decrease significantly, and the distribution of particles and pores tends to be uniform. The influence mechanism of principal stress axis rotation can be attributed to disturbance and failure of soil microstructure caused by principal stress axis rotation.
【作者单位】：浙江大学滨海和城市岩土工程研究中心;宁波万科房地产开发有限公司;
【基金】：国家自然科学基金项目(50778162;51178422;51078329)
【分类号】：TU442

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