砂沸现象的细观数值模拟及影响因素分析

采用饱和砂土流固耦合的细观力学模型,通过颗粒流数值模拟了在临界水力梯度条件下饱和砂土的细观响应.讨论了在建议模型框架内临界水力梯度、颗粒刚度等因素对模拟结果的影响,并从细观机理上做了进一步分析.模拟结果表明,在临界流或超临界流条件下,试样最终的稳态响应分成两部分:一部分颗粒停留在试样顶部,其颗粒数量正比于施加的水力梯度值;另一部分颗粒则在试样底部形成某种形式的对流运动.细观数值模型分析所得的临界水力梯度比连续介质力学分析得到的值要小,这个差别反映了模型的动力特性.在临界流或超临界流条件下,砂沸时水的流动除局部区域外基本上仍属于层流范围,但已偏离了达西定律.

Micro-numerical simulation of sand boil and analysis of its influencing factors

Particle flow code(PFC)simulation was performed to investigate meso-response of sand soil under critical flow condition using a coupled liquid-particle model.The effects of hydraulic gradient amplitude and particle stiffness were discussed and the occurrence of sand boil was analyzed from the viewpoint of micro-mechanism.The numerical results indicated that under critical or over-critical gradients,a layer of clustered particles formed near the top wall,and the remainder of the particles formed a suspension and underwent convective-like motion.The thickness of the top layer was proportional to the gradient amplitude.The gradient amplitude based on microanalysis was a little lower than that based on the traditional theory,which reflected the dynamic behaviour of the adopted model.The pore flow was mainly laminar but deviated from Darcy's law under critical or over-critical gradients.