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地震中土层运动是复杂的多维运动,土体遭受水平两方向的剪切作用,两方向剪切在大小和方向上相互耦合。针对上述问题,采用多向循环单剪系统(VDDCSS),研究循环剪切方向和剪应变幅值γ对软黏土剪切过程中剪切模量G和孔压u的影响。试验结果表明:由于土样的各向异性,不同方向的G是不同的;小γ下剪切作用会使下一次其他新方向的G稍微增大;大γ下剪切方向的变化会促进G的衰减(最多为单向剪切G衰减量的1.51倍),也会促进剪切过程中u的增大(最多为单向剪切u增加量的1.67倍);存在一个剪应变特征值γs,即当γ≤γs时,剪切作用会使其他新方向的G稍微增大,反之无此现象;剪切方向对G和u的影响程度随γ的增大而先增后减,剪切方向的变化极大地影响了循环孔压周期幅值uamp的发展;当0.1%<γ<2.0%时,再固结轴向变形△Hrc/H随γ的增大而增大,剪切方向使△Hrc/H在小γ下达到单向剪切时大γ时的值;当γ≥2.0%时,2种剪切方式下△Hrc/H趋于一致。
Soil movement in the earthquake is a complex multi-dimensional movement, the soil subjected to horizontal two-direction shear effect, the two directions of the shear coupling in size and direction. In view of the above problems, the influence of cyclic shear direction and shear strain amplitude γ on shear modulus G and pore pressure u during shearing of soft clay is studied by using VDDCSS. The experimental results show that due to the anisotropy of soil samples, G is different in different directions; G under a small γ will slightly increase the G in the next new direction; the change of the G (Up to 1.51 times the unilateral shear G attenuation), and also promote the increase of u in the shear process (up to 1.67 times of the increase of unidirectional shear u); there exists a shear strain eigenvalue γs , That is, when γ≤γs, the shearing effect will slightly increase G in other new directions, otherwise, the effect of shearing direction on G and u will increase first and then decrease with the increase of γ, When 0.1% <γ <2.0%, the axial deformation of re-consolidation ΔHrc / H increases with the increase of γ, and the direction of shear makes the amplitude of uamp of cyclic pressure cycle greatly affected. △ Hrc / H reaches the value of γ at unidirectional shearing at small γ; △ Hrc / H of both shearing modes tends to be consistent at γ≥2.0%.