波致ISS固化海床液化与剪切破坏特征分析

Analysis of Liquefaction and Shear Failure for ISS Solidifying Seabed Induced by Waves

以用于近海风机基础周围冲刷防护的离子固化土(ISS)为例,基于室内水槽试验和数学模型,计算波致海床超孔隙水压力和应力场,研究ISS固化海床液化与剪切破坏特征。结果表明,ISS固化层作为致密的板状结构设置于海床表面,不利于海床内部波致超孔隙水压力消散,导致海床更易发生累积液化,ISS固化海床深层液化所需的临界循环应力比χ_(cr)大于浅层;进行ISS固化海床液化深度设计时,以控制沿深度方向最大孔隙水压力位置处(z=-0.1h)的液化为目标,使该位置处的χ<χ_(cr),否则需调整ISS固化土的配比,重新进行液化验算;ISS固化层的设置促进了波致超孔隙水压力的累积,更易导致海床发生剪切破坏,剪切破坏应力角φ_(f)随深度增加而减小,剪切破坏深度随χ的增加而增大;对ISS固化海床进行剪切破坏深度验算时,可根据不同χ下φ_(f)的变化曲线确定某一深度是否会发生剪切破坏。

Taking the Ionic Soil Stabilizer(ISS)for scour protection around offshore wind turbine foundation as research object,based on the experimental wave flume test and numerical model,the characteristics of liquefaction and shear failure of ISS solidifying seabed was studied by calculating the excess pore water pressure and stress induced by waves respectively.The results indicate that the excess pore pressure is difficult to dissipate in ISS solidifying seabed with dense,plate structure,which is helpful to the residual liquefaction occurring.The critical cyclic stress ratioχ_(cr) for the onset of liquefaction in deep layer is larger than that of the shallow layer.It is advisable to take the location of the maximum excess pore water pressure(z=-0.1h)as control object for the liquefaction evaluation in ISS solidifying seabed,and make sure theχ<χ_(cr).Otherwise,it needs to change the proportion of ISS solidifying soil and recalculate the liquefaction.What’s more,the ISS solidifying layer hinders the dissipation of excess pore water pressure in seabed,and leads to the shear failure easily.The stress angle for shear failureφ_(f) decreases with the increase of the depth,and the depth of shear failure increases with the cyclic stress ratioχincreasing.It is practicable to evaluate the shear failure in ISS solidifying seabed according to the curves between the stress angle for shear failureφ_(f) and cyclic stress ratioχ.