复合地基垫层破坏模式的试验研究与数值模拟

Experimental study and numerical simulation of cushion failure mode in composite foundation

为了研究复合地基中不同厚度碎石垫层的破坏机理,在室内模型试验中,利用数字图像无标点量测技术,研究了复合地基碎石垫层的变形场与变形模式,得到了碎石垫层的变形范围、滑动面位置与形状,再现了碎石垫层破坏形成完整破坏滑移线的全过程.通过开发颗粒流程序,模拟室内模型试验中碎石垫层在加载过程中的破坏过程,并与模型试验结果进行了对比.结果表明:当垫层厚度小于桩径时,桩身中性点位置集中于0.2～0.4倍桩长处,垫层发生局部剪切破坏;当垫层厚度大于桩径时,桩身中性点位置集中于0.7～0.9桩长处,垫层发生整体剪切破坏.刚性桩复合地基碎石垫层破坏机理的揭示对于优化复合地基碎石垫层的设计具有重要的参考价值.

In order to study the failure mechanism of gravel cushion with different thickness in composite foundation,digital speckle correlation technique was used to in laboratory experiments study the deformation fields and modes of gravel cushion in composite foundation.The deformation scope,sliding position and shape of the gravel cushion were calculated.The whole process of the complete slip line caused by the cushion failure was observed.Particle flow code was developed to simulate the failure process of gravel cushion during the loading procedure.The experimental results were compared with the numerical analysis results.The comparison results show that when the cushion thickness is less than the pile diameter,the neutral point position of pile locates at the 20% to 40% of the pile length and the failure mode of cushion belongs to local shearing failure.When the cushion thickness is more than the pile diameter,the neutral point position of pile locates at the 70% to 90% of pile length and the failure mode of cushion belongs to general shearing failure.The revelation of the failure mechanism of gravel cushion in composite foundation with rigid piles has an important reference value for optimizing the design level of rigid composite foundation gravel cushion.