Numerical Simulation of Particle Flow Characteristics of Jacked Pile Penetration in Laminated Clay Soil
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摘要:
为深入探讨层状黏性土中静压桩的贯入机制，结合离散元PFC2D软件在处理大变形、非线性等问题的优势，考虑到接触黏结模型对模拟土体的优越性，建立了静压桩贯入层状黏土中的离散元模型，实现了离散元中静压桩的贯入过程；探讨了静压桩贯入过程中压桩力、桩端阻力、桩侧摩阻力以及桩侧径向压力随贯入深度的变化规律，从细观层次上分析了不同桩径的静压桩贯入层状土中土体接触力链的分布特征，明确了沉桩过程中土体位移的变化规律. 试验结果表明：随着桩径的增大，土层的变化对压桩力的影响逐渐减小；桩侧摩阻力和桩侧径向土压力的变化规律相似，在同一贯入深度处均出现明显的退化现象；不同土层接触力链的表现形式不同，桩端位于粉质黏土层时，桩端的影响范围约为7
D （D 为桩径），桩端位于粉土层时，桩端的影响范围约为9D ；粉质黏土中土颗粒主要以径向位移为主，而在粉土层中土颗粒位移受其上下土层的软硬程度制约.Abstract:To investigate the penetration mechanism of jacked piles in laminated clay and utilize the advantages of discrete element PFC2D software in dealing with large deformation and nonlinearity, given that the contact bonding model excels in soil simulation, a discrete element model for jacked pile penetration in laminated clay is established. The penetration process of jacked piles is realized in discrete element software. It is explored about how the pile force, pile end resistance, friction resistance and radial pressure at pile sides change with penetration depth in jacked pile penetration. The distribution characteristics of soil contact force chain are analyzed in the microscopic level for jacked pile penetration of different pile diameters. The variation law of soil displacement in jacking process is clarified. The test results show that, with the increase in pile diameter, the influence of soil layer on pile pressure decreases gradually. The friction resistance and radial earth pressure at pile sides are similar, and there is obvious degeneration at the given depth. Soil layers vary in the forms of contact force chains. When the pile end is located in the silty clay, the influence range of the pile end is about 7
D (D is pile diameter); when the pile end is located in the silty soil, it is about 9D . The clay particles in silty clay mainly show radial displacement. The displacement of soil particles in the silty soil is restricted by the hardness of the upper and lower soil layers.-
Key words:
- PFC2D /
- numerical simulation /
- jacked pile /
- laminated clay soil
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图 6 径向土压力随贯入深度变化曲线
Figure 6. Curves of radial earth pressure changing with penetration depth
图 8 侧摩阻力随贯入深度的变化曲线
Figure 8. Curves of lateral friction changing with penetration depth
表 1 土层细观参数
Table 1. Soil microscopic parameters
土层 土层名称 土层厚度/
cm密度/
（kg•m−3）法向接触刚度/
（×107 N•m−1）切向接触刚度/
（×107 N•m−1）法向黏结强度/N 切向黏结强度/N 摩擦系数 1 回填土（深黄色） 5 2720 1 1 500 250 0.270 2 粉土（深红色） 5 2710 5 5 500 250 0.756 3 粉质黏土（深蓝色） 5 2720 1 1 1000 500 0.320 4 粉质黏土（深棕色） 5 2720 1 1 1000 500 0.460 5 粉土（深灰色） 5 2710 5 5 500 250 0.790 6 粉质黏土（绿色） 5 2720 1 1 1000 500 0.502 7 粉土（黑色） 5 2710 5 5 500 250 0.780 8～12 砂土（橙色、紫色、青色、浅灰色、浅黄色） 25 2650 80 80 0.500 
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