地下管廊基坑开挖对CFG桩受力变形特性的影响研究

刘涛; 胡柏春; 杨迅

doi:10.11779/CJGE2022S1040

地下管廊基坑开挖对CFG桩受力变形特性的影响研究 English Version

中国电建集团贵阳勘测设计研究院有限公司, 贵州贵阳 558801

基金项目:

贵州省科技支撑项目黔科合支撑[2019]2853号

详细信息

作者简介:
刘涛(1988—)，男，硕士研究生，主要从事地下综合管廊方向研究及相关工程设计研究工作。E-mail: 1500492441@qq.com

中图分类号: TU431
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- PDF下载量: 30
出版历程
- 收稿日期: 2022-09-24
- 网络出版日期: 2023-02-06
- 刊出日期: 2022-11-30

Influences of excavation of foundation pit of underground pipe gallery on mechanical deformation characteristics of CFG piles

PowerChina Guiyang Engineering Corporation Limited, Guiyang 558801, China

摘要

摘要: 在先施工工程桩再进行开挖的基坑工程中，坑底土体在基坑开挖卸荷的过程中产生的回弹变形会导致基坑底部土体产生相对于桩体向上的位移，此时桩体可能因较大的拉力断裂，从而大大减弱地基承载力。以贵州某地下综合管廊项目为依托，利用有限元计算软件MIDAS GTS NX模拟了基坑开挖的施工过程，研究了桩长和桩体弹模对CFG桩受力及变形的影响规律。结果表明：桩长对CFG桩受力及变形有着较为明显的影响，而桩长超过一定范围后影响显著降低；增加桩体弹模会让桩体承受更大的拉应力，但是能使桩体处于更加安全的状态。
- 基坑开挖 /
- CFG桩 /
- 回弹变形 /
- 拉应力 /
- 数值模拟
Abstract: In the foundation pit in which the engineering piles are constructed first and then excavated, the rebound deformation of the soil at the bottom of the pit in the process of excavation and unloading will lead to the upward displacement of the soil at the bottom of the pit relative to the piles. At this time, the piles may be broken due to large tensile force, which will greatly reduce the bearing capacity of the foundation. Based on an underground comprehensive pipe gallery project in Guizhou, the construction process of excavation of foundation pit is simulated by using the finite element software MIDAS GTS NX, and the influence laws of length and elastic modulus of the piles on the stress and deformation of the CFG piles are studied. The results show that the length of the piles has obvious influences on the stress and deformation of the CFG piles, and the influences decrease significantly when the pile length exceeds a certain range. Increasing their elastic modulus will make the piles bear greater tensile stress, but it can make them be in a safer state.
- excavation of foundation pit /
- CFG pile /
- rebound deformation /
- tensile stress /
- numerical simulation

HTML全文

图 1 地下综合管廊施工图

Figure 1. Construction of underground pipe gallery

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图 2 基坑三维模型图

Figure 2. 3D model for foundation pit

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图 3 基坑计算模型横截面简图

Figure 3. Cross section of model for foundation pit

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图 4 基坑底部(土体)回弹量变化曲线

Figure 4. Variation curves of rebound amount at bottom of foundation pit (soil)

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图 5 桩顶竖向位移变化曲线

Figure 5. Curves of vertical displacement of pile top

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图 6 桩体拉应力分布

Figure 6. Distribution of tensile stress of piles

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图 7 基坑横截面最大拉应力变化曲线

Figure 7. Variation curves of maximum tensile stress of cross section of foundation pit

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图 8 基坑底部(土体)回弹量变化曲线

Figure 8. Variation curve of rebound amount at the bottom of foundation pit (soil)

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图 9 桩顶竖向位移变化曲线

Figure 9. Curves of vertical displacement of pile top

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图 10 基坑横截面最大拉应力变化曲线

Figure 10. Variation curves of maximum tensile stress of cross section of foundation pit

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图 11 拉应力与抗拉强度对比图

Figure 11. Comparison between tensile stress and strength

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表 1 土层参数取值表

Table 1 Values of parameters of soil layers

土层	重度/(kN·m^-3)	$E_{{\text{50}}}^{{\text{ref}}}$ /MPa	$E_{{\text{oed}}}^{{\text{ref}}}$ /MPa	$E_{{\text{ur}}}^{{\text{ref}}}$ /MPa	泊松比 $\nu$	黏聚力c/kPa	摩擦角 $\varphi$ /(°)
杂填土	19.0	30	30	90	0.32	5	28
黏土(可塑)	18.0	43	43	129	0.34	25	18
黏土(软塑)	17.3	22	22	66	0.34	20	15
强风化泥岩	24.0	120	120	360	0.37	30	20
注：表中 $E_{{\text{50}}}^{{\text{ref}}}$ 为三轴实验割线刚度； $E_{{\text{oed}}}^{{\text{ref}}}$ 为主压密加载试验的切线刚度； $E_{{\text{ur}}}^{{\text{ref}}}$ 为卸载弹性模量。

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表 2 计算步骤设置一览表

Table 2 List of calculation steps

施工阶段	施工阶段描述
第1步	初始地应力平衡
第2步	施工基坑围护结构与CFG桩
第3步	施工冠梁
第4步	施工内支撑（位移清零）
第5~10步	开挖至-6 m（每步开挖1 m）

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