土工织物包裹碎石桩力学特性的数值模拟研究

不同于普通碎石桩，土工织物包裹碎石桩受力变形过程因涉及到碎石与织物之间的相互作用而变得更为复杂。为研究包裹碎石桩强度及变形等力学特性，采用数值方法模拟土工织物包裹碎石桩的单轴与三轴压缩试验。通过对比试验数据验证数值模型的合理性，并在此基础上，分析土工织物模量、抗拉强度和围压对包裹碎石桩力学特性的影响，揭示包裹碎石桩体变形承载及破坏机制。结果表明：包裹碎石桩体在加载早期即已进入屈服状态，当织物发生拉伸破裂后包裹碎石桩体强度随即从峰值强度迅速下降；包裹碎石桩模量随土工织物模量呈线性增长，碎石相对密实度越高其模量增长幅度也越高；包裹碎石桩单轴抗压强度随土工织物抗拉强度线性增长，增长幅度与碎石相对密实度无关；在三轴压缩状态下得到的表观黏聚力随土工织物抗拉强度线性增加，与碎石相对密实度无关；土工织物抗拉强度对包裹碎石桩体的摩擦角几乎没有影响，其对包裹碎石桩体强度的提升主要以增加表观黏聚力的形式体现；围压和土工织物对碎石桩体约束作用发挥的先后顺序将改变包裹碎石桩三轴压缩状态下的应力-应变曲线形态；数值模型无法反映碎石颗粒对包裹织物带来的刺入及磨损，因此在土工织物包裹碎石桩数值模拟中必须对织物抗拉强度进行一定程度折减，否则数值模拟结果将极大高估其抗压强度。

Numerical Study on Mechanical Behaviors of Geotextile-wrapped Stone Column

Different from traditional stone columns, geotextile-wrapped stone columns show more complex behaviors related to the interaction between the stone column and geotextile. To study the strength and deformation behaviors of wrapped stone columns, uniaxial and triaxial compression tests on the geotextile wrapped stone column were numerically simulated in the proposed study. The numerical model was verified by comparing numerical results with the experiments. The influences of geotextile modulus, tensile strength, and confining pressure on the mechanical behaviors of the wrapped stone column were studied, revealing the deformation and bearing mechanism of the wrapped stone column. The wrapped stone column enters the yielding state at the early loading stage. Therefore, the bearing capacity of the wrapped stone column rapidly decreases once the geotextile ruptures. The modulus of the wrapped stone column increases linearly with the geotextile modulus; the higher the relative compactness of the stone column, the higher the increase in the modulus. The uniaxial compressive strength increases linearly with the geotextile tensile strength and is not strongly influenced by the relative compactness of the stone column. The appearance cohesion of the wrapped stone column obtained from the triaxial compression tests increases linearly with the geotextile tensile strength. The tensile strength of the geotextile has almost no effect on the friction angle of the stone column, and its improvement on the strength of the stone column is mainly reflected in increasing the apparent cohesion. The confining pressure and geotextile significantly affect the stress-strain curves of the wrapped stone column because the confining effect is not activated at the same time. The numerical model cannot reflect the damage to the geotextile caused by abrasion. Therefore, in the numerical simulation of the geotextile wrapped stone column, the tensile strength of the geotextile must be reduced to a certain extent.