原状及重塑黄土双轴试验微观力学特征离散元模拟

井旭; 谢婉丽; 单帅

doi:10.19509/j.cnki.dzkq.2021.0311

原状及重塑黄土双轴试验微观力学特征离散元模拟

doi: 10.19509/j.cnki.dzkq.2021.0311

基金项目:

陕西省国际科技合作与交流计划重点项目 2019KWZ-02

国家自然科学面上基金 4197020993

国家重点研发课题 2017YFD0800501

国家自然科学基金资助项目 41772323

详细信息

作者简介:
井旭(1995-), 男, 现正攻读地质工程专业硕士学位, 主要从事岩土工程数值模拟研究工作。E-mail: jingxu@cug.edu.cn

通讯作者:
谢婉丽(1974-), 女, 教授, 主要从事地质灾害治理、黄土微观结构方面的研究工作。E-mail: xiewanli@nwu.edu.cn

中图分类号: P511
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出版历程
- 收稿日期: 2020-08-14

Discrete element simulation study on micromechanical characteristics of undisturbed and remolded loess in biaxial test

摘要

摘要: 黄土作为一种特殊的颗粒材料，微观上颗粒组成的结构决定了其力学特性。原状及重塑黄土因结构的差异而具有不同的力学特性。针对黄土结构性如何影响其力学特征这一基本问题，开展基于电镜扫描获取细观颗粒信息，同时考虑颗粒形状、颗粒破碎可能性进行建模的离散单元法进行原状黄土和饱和重塑土在恒定应变速率双轴试验下的宏观力学和细观力学性能研究。研究结果显示：试样微观结构的差异对变形破坏过程产生显著影响。当轴向应力较低时原状黄土及重塑黄土力链多分布于大型骨架颗粒附近，随着轴向应力增加，原状黄土力链形成网状图案但仍具备主要传导区域，重塑黄土无明显主要传导区，呈现均匀网状。原状土及重塑土骨架颗粒簇周围多形成张拉裂隙，剪切裂隙多数形成于骨架颗粒簇内部，又以颗粒簇相互挤压接触时最为明显。使用该建模方法，可以有效反映原状及重塑黄土由于内部结构组成差异导致相同应力条件下产生的不同内部应力状态。基于以上研究结论，给出了黄土结构性对宏观强度影响的微观解释。研究成果可为黄土地区地质灾害防治提供一定依据。使用该建模方法，可以有效反映原状及重塑黄土由于内部结构组成差异导致相同应力条件下产生的不同内部应力状态。基于以上研究结论，给出了黄土结构性对宏观强度影响的微观解释。
- 黄土 /
- 微观力学特征 /
- 双轴试验 /
- 柔性簇 /
- 离散元模拟
Abstract: Loess is a special granular material, and its mechanical properties are determined by the microscopic structure of granules. The undisturbed and remolded loess have different mechanical properties due to the difference in structure. In order to solve the basic problem of how the structural properties of loess affect its mechanical characteristics, based on scanning electron microscopy (SEM) to study the macroscopic and microscopic mechanical properties of undisturbed loess and saturated remolded loess under constant strain rate biaxial test, while considering the shape of particles and the possibility of particle breakage. The simulation results show that when the stress is low, the undisturbed loess and the remolded loess force chains are mostly distributed near the large framework particles. With the increase of stress, the undisturbed force chains form a network pattern but still have the main conduction region, while the remolded loess has no obvious major conduction region and presents a uniform mesh. Under the same confining pressure and strain, the number of cracks in the undisturbed loess is lower and they are concentrated in the shear zone. The number of cracks in the remolded loess is more but more uniform.Tension cracks are mostly formed around the clusters of undisturbed loess and remolded loess. Shear cracks are mostly formed inside the clusters of framework particles, and the most obvious is when the clusters of particles are in contact with each other. Using this modeling method can effectively reflect the different internal stress states of undisturbed and remolded loess under the same stress condition due to the difference in internal structure composition. Based on the above research conclusions, a microscopic explanation of the influence of loess structure on the macroscopic strength is given. The research results can provide a certain basis for the prevention and control of geological disasters in the loess area.
- loess /
- micromechanical characteristics /
- biaxial test /
- flexible cluster /
- discrete element simulation

HTML全文

图 1 三轴试验后试样照片

a.原状样；b.重塑样

Figure 1. Sample picture after triaxial test

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图 2 黄土微结构特征及分布

a.原状黄土; b.重塑黄土

Figure 2. Microstructure characteristics and distribution of loess

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图 3 最大及最小费雷特直径示意图

Figure 3. Schematic diagram of the maximum and minimum Feret diameters

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图 4 黏结模型示意图

a.平行黏结b.接触黏结

Figure 4. Schematic diagram of bonding model

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图 5 试样离散元建模

a.原状黄土离散元模型; b.重塑黄土离散元模型

Figure 5. Sample discrete element modeling

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图 6 双轴试验示意图

Figure 6. Schematic diagram of biaxial test

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图 7 PFC材料不同围压下应力-应变曲线

Figure 7. Stress-strain curves of PFC material under different confining pressures

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图 8 原状黄土力链图

Figure 8. Undisturbed loess force chain diagram

a.σ₃=50 kPa; b.σ₃=100 kPa; c.σ₃=200 kPa; d.σ₃=400 kPa

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图 9 重塑黄土力链图

Figure 9. Remolded loess force chain diagram

a.σ₃=50 kPa; b.σ₃=100 kPa; c.σ₃=200 kPa; d.σ₃=400 kPa

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图 10 原状黄土剪切裂隙分布图

Figure 10. Distribution map of undisturbed loess shear cracks

a.σ₃=50 kPa; b.σ₃=100 kPa; c.σ₃=200 kPa; d.σ₃=400kPa

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图 11 重塑黄土剪切裂隙分布图

Figure 11. Distribution map of shear cracks in remolded loess

a.σ₃=50 kPa; b.σ₃=100 kPa; c.σ₃=200 kPa; d.σ₃=400kPa

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图 12 原状黄土拉张裂隙分布图

Figure 12. Distribution of tensile fissures in undisturbed loess

a.σ₃=50 kPa; b.σ₃=100 kPa; c.σ₃=200 kPa; d.σ₃=400 kPa

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图 13 重塑黄土拉张裂隙分布图

Figure 13. Distribution map of tensile cracks in remolded loess

a.σ₃=50 kPa; b.σ₃=100 kPa; c.σ₃=200 kPa; d.σ₃=400 kPa

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图 14 原状黄土裂隙数量变化曲线

Figure 14. Curve of the number of cracks in undisturbed

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图 15 重塑黄土裂隙数量变化曲线

Figure 15. Curve of the number of cracks in remolded

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表 1 土体宏观力学参数

Table 1. Macroscopic mechanical parameters of loess

	密度ρ/(g·cm^-3)	孔隙比e	黏聚力c/ kPa	内摩擦角φ/(°)
原状土	1.62	0.85	55.8	15.9
重塑土	1.62	0.81	39.3	8.8

下载: 导出CSV

表 2 PFC模型细观参数

Table 2. Micro-parameters of PFC model

土样	参数	几何颗粒	球颗粒	几何-球	碎屑及团粒
原状土	法向刚度/(N·m^-1)	1.5×10¹⁰	1.5×10¹⁰	1.5×10¹⁰	-
	剪切刚度/(N·m^-1)	1.0×10¹⁰	1.0×10¹⁰	1.0×10¹⁰	-
	有效模量/(N·m^-2)	2.0×10⁷	2.0×10⁷	2.0×10⁷	-
	刚度比	1.0	1.0	1.0	-
	平行黏结有效模量/(N·m^-2)	2.0×10⁷	2.0×10⁷	2.0×10⁷	-
	平行黏结刚度比	1.0	1.0	1.0	-
	颗粒摩擦系数	0.5	0.5	0.5	-
	法向黏结刚度/(N·m^-1)	1.5×10⁶	8.0×10⁵	8.0×10⁵	-
	切向黏结刚度/(N·m^-1)	1.5×10⁶	1.5×10¹⁰	8.0×10⁵	-
	黏结力/(N·m^-1)	3.5×10⁵	1.3×10⁵	1.3×10⁵	-
重塑土	法向刚度/(N·m^-1)	1.5×10¹⁰	1.5×10¹⁰	1.5×10¹⁰	1.5×10¹⁰
	剪切刚度/(N·m^-1)	1.0×10¹⁰	1.0×10¹⁰	1.0×10¹⁰	1.0×10¹⁰
	有效模量/N·m^-2)	2.0×10⁷	2.0×10⁷	2.0×10⁷	2.0×10⁷
	刚度比	1.0	1.0	1.0
	平行黏结有效模量/(N·m^-2)	2×10⁷	-	2×10⁷	2×10⁷
	平行黏结刚度比	1.0	-	1.0	1.0
	颗粒摩擦系数	0.5	0.5	0.5	0.5
	法向黏结刚度/(N·m^-1)	1.4×10⁶	6.0×10⁶	6.9×10⁵	6.9×10⁵
	切向黏结刚度/(N·m^-1)	1.4×10⁶	6.0×10⁶	6.9×10⁵	6.9×10⁵
	黏结力/(N·m^-1)	3.0×10⁵	-	1.5×10⁵	1.5×10⁵

下载: 导出CSV

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