包裹碎石桩承载特性试验研究

为了研究包裹碎石桩的承载机制，开展了室内模型试验，对不同套筒长度和刚度的包裹碎石桩承载力、端阻力、变形和破坏情况等进行了分析。试验中利用自制的桩体径向变形测量仪监测了桩体的径向变形情况。试验结果表明：当桩体支承在坚硬土层时，全长包裹碎石桩有效提高碎石桩的承载力和刚度，且采用弹性模量较大的土工材料套筒，包裹碎石桩的极限承载力和刚度也较大，部分包裹碎石桩（包裹长度为0.6倍桩长）相对于碎石桩优势不明显。这是因为部分包裹碎石桩和全长包裹的承载特性、变形特点和破坏模式均存在差异。全长包裹碎石桩传递至桩底端的荷载大于部分包裹碎石桩和碎石桩的。与部分包裹碎石桩和碎石桩比较，全长包裹碎石桩桩身变形分布较为均匀，同一应力作用下，桩身最大径向变形量较小。此外，全长包裹碎石桩刺入顶部褥垫层发生破坏，而部分包裹碎石桩发生鼓胀破坏。

Experimental analysis of bearing behavior of geosynthetic encased stone columns

A model experiment is conducted to study the bearing mechanism of geosynthetic encased stone columns. Bearing capacity, end resistance, deformation, destruction of the columns with different stiffnesses and lengths of encasements are analyzed. The radial deformation of the columns is measured by self-made radial deformation measurement instruments in the experiment. It can be found from the experiment results that the fully encased stone columns effectively improve the bearing capacity and stiffness of the stone column installing on hard soil layer. And the one with a larger modulus of elasticity of encasement material has the higher bearing capacity and stiffness. However, the partially encased stone column with an encasement length of 60% of the column length does not have significant advantages over the stone column. This is because the load capacity characteristic, deformation property, and failure mode of the fully encased stone column are different from those of the partially encased stone column. The load transmitted to the fully encased stone columns tip is higher than that of the partially encased stone column and the stone column. The deformation along the fully encased stone columns distributes more uniform compared to that of the partially encased stone column. And the maximum radial deformation along the fully encased stone column is lower at a certain pressure. What's more, the fully encased stone columns fail from penetrating into the upper cushion; while the uncased part of the partially encased stone column undergoes excess bulging.