考虑土塞效应的开口管桩沉桩与承载全过程离散元分析

李立辰; 刘卓; 刘浩; 吴文兵; 罗仑博; 蒋国盛; 梅国雄

doi:10.11779/CJGE20230340

考虑土塞效应的开口管桩沉桩与承载全过程离散元分析 English Version

李立辰^1,,
刘卓¹,
刘浩¹,
吴文兵^1, ,,
罗仑博²,
蒋国盛¹,
梅国雄^{1, 3}

1.
中国地质大学(武汉)工程学院岩土钻掘与防护教育部工程研究中心, 湖北武汉 430074
2.
中国长江三峡集团有限公司科学技术研究院，北京 101100
3.
浙江大学海洋学院，浙江舟山 316021

基金项目:

国家自然科学基金项目 52178371

国家自然科学基金项目 52308383

湖北省自然科学基金青年项目 2023AFB008

中国博士后科学基金面上项目 2022M712964

详细信息

作者简介:
李立辰(1994—)，男，博士，助理研究员，主要从事桩基工程理论与技术方面的教学与科研工作。E-mail: 20121003645@cug.edu.cn

通讯作者:
吴文兵, E-mail: zjuwwb1126@163.com

中图分类号: TU470
计量
- 文章访问数: 474
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出版历程
- 收稿日期: 2023-04-18
- 网络出版日期: 2023-11-29
- 刊出日期: 2024-06-30

DEM analysis of installation and bearing process of open-ended piles considering plugging effects

1.
Faculty of Engineering, Engineering Research Centre of Rock-Soil Drilling & Excavation and Protection, Ministry of Education, China University of Geosciences, Wuhan 430074, China
2.
Institute of Science and Technology, China Three Gorges Corporation, Beijing 101100, China
3.
Ocean College, Zhejiang University, Zhoushan 316021, China

摘要

摘要: 开口管桩贯入过程中会产生复杂的土塞效应，显著影响管桩的沉桩过程与承载特性。考虑到试验方法成本高、周期长、且难以直观反映土塞与管桩的相互作用特性，基于离散元方法开展砂土地基中静压开口管桩沉桩与承载全过程模拟分析。基于室内试验数据对离散元模型参数进行标定，并采用周期性单元复制法生成均质且应力沿深度线性分布的地基模型。基于土体变形特征，揭示管桩中土塞的主动拱与被动拱分布特征。进一步地，结合土塞参数的演化规律，得出土塞增长率（IFR）对土塞状态变化更为敏感，且土塞阻力的发挥趋势与IFR值变化趋势有较高的相似性。基于管桩静载试验模拟，得出静载下开口管桩呈完全闭塞状态，土塞的荷载-位移响应呈弹塑性，并最终建立考虑CPT锥尖阻力、土塞效应、管桩尺寸的静压开口管桩桩端阻力经验计算公式。本文研究成果揭示了土塞的形成演化过程与承载机制，对于考虑土塞效应的开口管桩沉桩阻力预测与承载力计算具有一定参考价值。
- 开口管桩 /
- 土塞效应 /
- 离散元法 /
- 桩端阻力
Abstract: The penetration process of open-ended piles will cause complex plugging effects, which further influence the installation and bearing characteristics of piles. Considering the high cost, long period and limitations in reflecting the interaction between piles and soil plugs of the traditional experimental approach, the jacking installation and subsequent loading process of open-ended piles in sand are simulated based on the discrete element method (DEM). The periodic cell replication method is used to generate a homogeneous foundation sample with linear stress distribution. Based on the analysis of the soil deformation characteristics, the characteristics of the active arch and passive arch distribution of the soil plugs are revealed. Based on the analysis of the evolution of soil plugging parameters and plug bearing characteristics, it is found that the incremental filling ratio (IFR) is more sensitive to the plug behavior, and the development of plug resistance shows good consistency with the trend of the IFR value. Also, the open-ended piles are in the fully plugged mode under the static loads, and the load-displacement response of soil plugs is elastic-plastic. Finally, the method for calculating the end bearing capacity of open-ended jacked piles is established by considering the CPT cone resistances, plugging effects and pile size effects. The above results reveal the evolution process and bearing mechanism of soil plugs and can provide reference value for the prediction of installation resistance and calculation of bearing capacity of open-ended piles considering soil plugging effects.
- open-ended pile /
- plugging effect /
- discrete element method /
- end bearing capacity

HTML全文

图 1 应力应变曲线标定结果

Figure 1. Calibrated results of stress-strain response

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图 2 地基模型示意图

Figure 2. Schematic view of soil foundation

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图 3 初始平衡状态下地基参数沿深度分布特征

Figure 3. Distribution of foundation parameters at balance

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图 4 不同贯入速度下P2沉桩总阻力发展特征

Figure 4. Development of installation resistance for P2 under different penetration speeds

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图 5 沉桩结束时桩周土体变形特征

Figure 5. Soil deformations around piles at the end of pile installation

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图 6 沉桩过程中桩端土体运移轨迹特征

Figure 6. Particle movements relative to pile tip during pile Installation

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图 7 土塞参数随贯入深度变化特征

Figure 7. Development of soil plugging parameter with penetration.depth

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图 8 土塞增长率与土塞率经验拟合关系

Figure 8. Relationship between IFR and PLR

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图 9 沉桩阻力随贯入深度变化特征

Figure 9. Development of pile installation resistance with penetration depth

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图 10 单位内摩阻力随贯入深度变化特征

Figure 10. Development of unit inner shaft resistance with penetration depth

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图 11 内摩阻力沿桩身分布特征

Figure 11. Distribution of inner shaft resistance

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图 12 承载结束时桩周土体变形特征

Figure 12. Soil deformations around pile at the end of static loading

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图 13 桩顶位移对贯入阻力的影响

Figure 13. Development of penetration resistance with displacement of pile head

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图 14 q_plug/q_c和q_ann/q_c与IFR经验拟合关系

Figure 14. Relationship between q_plug/q_c, q_ann/q_c and IFR

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图 15 归一化桩端阻力(q_b/q_c)经验拟合关系

Figure 15. Normalized relationship between q_b/q_c and A_{rb, eff}

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表 1 UWA硅质砂及其等效离散砂样参数

Table 1 Properties of UWA superfine sand and its DEM analogue

参数	G_s	颗粒尺寸/mm			C_u	C_c	${\varphi '_{{\text{cs}}}}$ /(°)
参数	G_s	d₁₀	d₅₀	d₆₀	C_u	C_c	${\varphi '_{{\text{cs}}}}$ /(°)
试验值	2.67	0.12	0.18	0.20	1.67	1.020	33
模拟值	2.67	1.80	2.70	3.00	1.67	0.975	32
注： ${\varphi '_{{\text{cs}}}}$ 为极限状态摩擦角，C_u，C_c分别为不均匀系数和曲率系数。

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表 2 离散元模型参数

Table 2 Parameters for discrete model

地基土样								墙		桩
k_n/(N·m^-1)	k_s/(N·m^-1)	μ	$\gamma$	μ_r	β_n	β_s	M_d	k_n/(N·m^-1)	k_s/(N·m^-1)	μ_w	k_n/(N·m^-1)	k_s/(N·m^-1)	μ_p
1×10⁸	2×10⁷	0.5	0.1	0.45	0.1	0.1	3	1×10¹⁰	1×10¹⁰	0	1.5×10⁹	1.5×10⁹	0.5
注：k_n，k_s分别为法向刚度和剪切刚度；μ为摩擦系数； $\gamma$ 为阻尼比；μ_r为滚动摩擦系数；β_n为法向极限阻尼比；β_s为剪切极限阻尼比；M_d为黏壶模式；μ_w为墙摩擦系数；μ_p为桩摩擦系数。

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