DEM analysis of mechanism and evolution of horizontal soil arching between piles in sand slopes
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摘要: 抗滑桩等非连续支挡结构在边坡工程中依靠土拱效应安全经济地发挥支护功能。鉴于不同类型砂土的力学性质差异较大，为揭示密砂与松砂土质边坡抗滑桩桩间水平土拱机理与演变规律，采用离散元方法（DEM）模拟支挡砂土水平土拱的成拱过程。在传统力链分析的基础上，提出通过筛选高应力颗粒来研究土拱的形成过程，进一步从细观角度对不同工况土拱效应进行分析，以揭示“应力拱”和“位移拱”的演化过程。研究表明：密砂和松砂中的水平土拱的动态演变过程均表现为3个演化阶段，分别对应于密砂和松砂的剪切性状，即应变软化和应变硬化现象，揭示了砂土边坡桩间土拱效应的演变规律。此外，讨论了宏-微观DEM模拟参数对土拱形成过程与土拱效应性能的影响，结果表明拱跨对于荷载传递效率的影响最大。Abstract: The non-continuous retaining structures such as anti-slide piles rely on the soil arching effects to provide support safely and economically in slope engineering. Considering the significant differences in the mechanical properties of sands, to reveal the mechanism and evolution patterns of horizontal soil arching between piles in sand slopes, the discrete element method (DEM) is used to simulate the formation process of horizontal soil arching. On the basis of the traditional force chain analysis, it is proposed to study the formation process of soil arching by screening high stress particles. Furthermore, the analysis of the soil arching effects under different conditions from a microscopic point of view is conducted to reveal the evolution process of "stress arching" and "displacement arching". The results demonstrate that the dynamic evolution of horizontal arching in both dense and loose sands can be divided into three evolutionary stages, corresponding to the shear behaviors of the two sands, i.e., strain softening and strain hardening phenomena, which reveals the evolution patterns of the soil arching effects in the sand slopes. Additionally, the influences of macro-micro DEM simulation parameters on the arching process and performance are discussed. The results indicate that the arching span has the greatest impact on the load transfer efficiency.
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图 2 50 kPa围压下的砂土剪切性状及参数标定
Figure 2. Shear behaviours of sands under confining stress of 50 kPa and parameter calibration
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图 3 三维土拱效应问题的平面应变模型简化示意图
Figure 3. Simplified schematic diagram of soil arching from three-dimensional to plane strain model
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图 7 力链及高应力颗粒分布特征
Figure 7. Distribution features of contact force chains and high-stress particles
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图 8 土拱形成过程中的应力重分布和颗粒位移
Figure 8. Stress redistribution and particle displacement during formation of soil arching
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图 9 不同加载位移时拱跨中线上σx分布
Figure 9. Distribution of σx along midline of arching span at different loading displacements
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图 12 3组加载速度下的Wtop和Fp演变
Figure 12. Evolution of Wtop and Fp under three loading velocities
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图 13 加载速度为2a/5·s-1时的端承拱和摩擦拱受力
Figure 13. Forces of end-bearing arching and friction arching at loading velocity of 2a/5·s-1
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图 14 加载速度为2a/5·s-1时荷载传递效率EA演变
Figure 14. Evolution of efficacy EA at loading velocity of 2a/5·s-1
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图 15 荷载传递效率EA小提琴图及其在不同加载速度下EA的变化曲线
Figure 15. Violin plot of arching efficiency EA and its variation curve under different loading velocities
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图 16 拱跨比对荷载传递效率EA和端承拱承担比(N/Fp)的影响
Figure 16. Influences of arching span ratio on arching efficacy EA and efficacy of end-bearing arching (N/Fp)
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图 17 50 kPa围压下的不同摩擦系数的砂土剪切性状
Figure 17. Shear behaviours of sands with different friction coefficients under confining stress of 50 kPa
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图 18 不同摩擦系数的推力Wtop和土拱荷载传递效率EA演变
Figure 18. Evolution of thrust Wtop and arching efficacy EA for different friction coefficients
表 1 DEM模型的微观参数
Table 1 Mesoscopic parameters of DEM model
参数 法向刚度/
(N·m-1)切向刚度/
(N·m-1)摩擦系数 颗粒密度/
(kg·m-3)最大粒径/
mm最小粒径/ mm 平均粒径/ mm 孔隙度 砂土(ball) 1.0×107 1.0×107 1.0 2500 1.2 0.5 0.78 0.25 边界(wall) 1.0×1012 1.0×1012 0 — — — — — 拱脚(wall) 1.0×109 1.0×109 5.0 — — — — — 
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