自钻式原位剪切旁压模型PFC<sup>3D</sup>细观模拟

张亚飞; 徐光黎; 侯天顺; 胡焕忠

doi:10.3799/dqkx.2015.173

自钻式原位剪切旁压模型PFC^3D细观模拟

doi: 10.3799/dqkx.2015.173

1.
西北农林科技大学水利与建筑工程学院, 陕西杨凌 712100
2.
中国地质大学工程学院, 湖北武汉 430074
3.
武汉中交岩土工程有限责任公司, 湖北武汉 430052

基金项目:

国家自然科学基金项目 41072218

西北农林科技大学博士启动基金项目 Z109021507

详细信息

作者简介:
张亚飞(1987-), 男, 讲师, 主要从事土体原位测试方面的研究工作.E-mail: zhangyafei00111@163.com

中图分类号: P64
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出版历程
- 收稿日期: 2015-02-19
- 刊出日期: 2015-11-15

PFC^3D Mesoscopic Simulation of Self-Boring In-Situ Shear Pressure-Meter Model Test

1.
College of Water Resources and Architectural Engineering, Northwest A&F University, Yangling 712100, China
2.
Faculty of Engineering, China University of Geosciences, Wuhan 430074, China
3.
China Communication Geo-Technical Engineering Co.Ltd. Wuhan, Wuhan 430052, China

摘要

摘要: 自钻式原位剪切旁压试验(self-boring in-situ shear pressure-meter)以其独特的多级加载方式, 能够直接测出土体的强度和变形参数, 然而, 目前对探头周围土体变形机理研究较少.为揭示自钻式原位剪切旁压仪试验过程中测定器周围土颗粒变形机理, 应用PFC^3D(particle flow code in three dimensions)颗粒流程序对自钻式原位剪切旁压试验进行了仿真数值模拟, 对多级加载过程中探头周围土体的位移场和应力场发展变化以及数值试样各阶段变形模量和土颗粒运动轨迹进行了分析研究.试验结果表明: 随着剪应力的逐级施加, 中间区域颗粒的位移量不断增大, 且位移矢量方向性更加显著.径向应力在探头附近两侧形成近似呈对称分布的数个"应力核"; 竖向应力在探头两侧形成扁平状应力带, 且在肩部形成应力集中区.中部区域球颗粒的运动轨迹成台阶状, 且随距探头距离的增大由近到远可分为3个特征区域; 球颗粒的Z向和XY向位移量亦随之呈负指数形式衰减, Z向位移量衰减速率更快.
- 自钻式原位剪切旁压试验 /
- 颗粒流 /
- 土体应力 /
- 变形模量 /
- 运动轨迹 /
- 岩土工程 /
- 工程地质学.
Abstract: The self-boring in-situ shear pressure-meter test can obtain the strength and deformation parameters directly through its unique multi-level loading mode; however, the deformation mechanism of the soil surrounding the probe has seldom been studied. To reveal the deformation mechanism of the sand sample surrounding the probe of the self-boring in-situ shear pressure-meter (SBISP) during the loading process, the SBISP model test is simulated by PFC^3D (particle flow code in three dimensions) program in this study. The development of the displacement and stress field of the soil surrounding the probe, as well as the deformation modulus of each grade of the numerical sample and the motion trails of the soil particles, are studied under multi-level loading process. The results of numerical experiments show that the displacement of particles in central area increases with the shear stress imposed stepwise, and the direction of displacement vector shows a clearly preferred direction. Several radial stress cores of approximately symmetrical distribution have formed near both sides of the probe. At the same time, the vertical stress has formed flat stress zones, and it has produced some stress concentration areas in the shoulder of the probe. The motion trails of the particles are step-like lines in the central area which can be divided into three characteristic zones as the distance to the probe increases. The vertical and horizontal displacements of particles descend in a negative exponential form, but the vertical displacement has a faster attenuation rate.
- self-boring in-situ shear pressure-meter test /
- particle flow /
- soil stress /
- deformation modulus /
- motion trail /
- geotechnical engineering /
- engineering geology.

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图 1 大型三轴土槽示意

Fig. 1. Sketch of triaxial chamber with probe of SBISP

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图 2 模型边界及探头示意

Fig. 2. Sketch of the model boundary and probe

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图 3 SBISP颗粒流数值试样

Fig. 3. PFC^3D numerical sample of SBISP

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图 4 SBISP现场试验曲线

Fig. 4. The field test curve of SBISP

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图 5 SBISP试验颗粒流数值模拟曲线(σ_V=80 kPa)

Fig. 5. Numerical simulation curve of SBISP tests

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图 6 球颗粒位移量与对应颜色关系

Fig. 6. The corresponding colors for different displacement of particles

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图 7 各级径向应力作用下颗粒位移等值线

Fig. 7. Displacement contour sketch of numerical sample under different radial stresses

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图 8 颗粒位移矢量分布与位移等值线对比

Fig. 8. Comparison of the distribution of displacement vectors of particles and the contour map under shear stress of each grade

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图 9 探头周围土体应力分布

Fig. 9. Contours of soil stress

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图 10 各级径向应力与探头半径关系

Fig. 10. Relation of the radius of the probes and the radial stress of each grade

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图 11 SBISP试验变形模量实例

Fig. 11. The deformation modulus example of SBISP field test

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图 12 不同距离处球颗粒运动轨迹

id表示监测球的编号; r表示监测球距测定器中心的距离.各球运动轨迹在XZ面上的投影用黑色线表示; 各球运动轨迹在XY面上的投影用蓝色线表示

Fig. 12. Motion trails of particles located in different distances

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图 13 球颗粒Z向和XY向位移量变化趋势

Fig. 13. Vertical and horizontal displacement of particles in different distances

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表 1 冈垣砂物理性质指标

Table 1. Physical property indexes of okagaki sand

项目	颗粒密度ρ_s(g/cm³)	平均粒径D₅₀(mm)	有效粒径D₁₀(mm)	不均匀系数U_c	最大孔隙比e_max	最小孔隙比e_min
冈垣砂	2.63	0.26	0.16	2.2	0.94	0.56

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表 2 模型墙细观参数

Table 2. Meso-parameters of model wall

墙编号	法向刚度k_n(N·m^-1)	切向刚度k_s(N·m^-1)	摩擦系数f_c
1	1×10¹⁰	1×10¹⁰	0.6
2、3、5、6、7、8	1×10¹⁰	-	-

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表 3 数值试样分区及细观参数

Table 3. Partitions and meso-parameters of numerical sample

区域	D的倍数范围	粒径(mm)	法向刚度k_n(N·m^-1)	颗粒密度ρ_s(kg·m^-3)	摩擦系数f_c
中间区域	1~10	2.0~3.2	2.0×10⁵	2 630	1.0
外围区域	10~14	5.0~6.2	4.3×10⁵	2 630	1.0
注：D为探杆直径.

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