【摘要】 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。更多还原

【Abstract】 The ground motion in earthquake is a complex and multi-dimensional movement. The ground soil experiences the horizontal shearing in two directions with the shear directions and the magnitudes of the loading both coupling. The effect of cyclic shear direction and shear strain amplitude γ on the shear modulus G and the pore pressure u were therefore investigated to the saturated soft clay during the shear process and compression in the reconsolidation process with the VDDCSS system. The shear modulus G was found to be different in different directions due to the soil anisotropy. The shear test with small γ made G increased slightly in other directions. The changing of shear direction accelerated the declining of G(1.51 times of unidirectional attenuation of G) and promoted the development of u in the shear process(1.67 times of the increment of the unidirectional pore pressure u). The shear tests with γ greater than a value γs had no such phenomenon. The changing of shear direction influenced greatly the amplitude of pore pressure uamp. When 0.1%<γ <2.0%,the reconsolidation settlement △Hrc/H increased with the increasing of γ. The changing of shear direction promoted the △Hrc/H at the small γ and reached a value which was reached at the large γ in uni-directional shear;when γ ≥2.0%,the △Hrc/H under 2 kinds of shear-mode tended to be the same.更多还原