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以宁波(4)2层黏土为对象,在单双向两种不同振动模式下,通过不同围压及不同动应力比条件下的动三轴剪切试验,研究宁波软土的动力特性以及振后强度弱化特性。试验结果表明:单向振动模式下(不产生拉应力)产生的动弹性模量衰减、累积塑性应变比双向振动条件下(产生拉应力)的发展显著,但双幅弹性应变发展较弱;在振后剪切阶段,双向振动使得试样产生拉应力,振后抗剪强度弱化比单向振动明显;单向振动模式下,试样发生剪胀,围压越大,剪胀程度减弱直至消失,孔压-轴向应变曲线存在峰值,表现出类超固结土特性;确定了在两种振动模式下,适用于宁波(4)2层黏土的振后弱化参数。
Taking Ningbo (4) 2-layer clay as an example, dynamic and triaxial shear tests under different confining pressures and different dynamic stress ratios were carried out under two different vibration modes of single and two directions to study the dynamic characteristics of Ningbo soft soil and the influence of vibration Strength weakening characteristics. The experimental results show that the dynamic elastic modulus decreases under unidirectional vibration mode (no tensile stress), and the cumulative plastic strain ratio develops significantly under the bi-directional vibration (tensile stress) In the post-shearing stage, the specimens were subjected to two-way vibration, which resulted in tensile stress. After the vibration, the shear strength was weaker than the unidirectional vibration. Under the unidirectional vibration mode, the specimen dilatancy, the confining pressure increased, The pore-pressure-axial strain curve has the peak value, which shows the characteristics of the over-solidified soil. The post-vibrational weakening parameters suitable for the two-layer clay of Ningbo (4) are determined under the two vibration modes.