软土地区桩基横向抗力系数的精细化取值研究

张俊云; 张乐; 冯君

doi:10.11779/CJGE2021S2048

软土地区桩基横向抗力系数的精细化取值研究 English Version

西南交通大学土木工程学院,四川　成都　610031

基金项目:

四川省科技计划重点项目 2021YFS0321

详细信息

作者简介:
张俊云(1974— ),男,博士,副教授,主要从事土力学与基础工程方面的教学和科研。E-mail: zjy74@126.com

中图分类号: TU473.1
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出版历程
- 收稿日期: 2021-08-14
- 网络出版日期: 2022-12-05
- 刊出日期: 2021-10-31

Refined value of lateral resistance coefficient of pile foundation in soft soil areas

School of Civil Engineering, Southwest Jiaotong University, Chengdu 610031, China

摘要

摘要: m法是横向受荷桩桩身变形和内力分析的一种常用方法。在没有试桩的条件下,m法中横向抗力系数的比例系数m值只能根据地基土的类型等从规范推荐的较大范围中取值,对工程经验依赖性强,具有较大的随机性。将沪通铁路沿线主要软土按压缩特性分为11亚类,通过有限元模拟分析了水平力H、泥面（桩顶）水平位移和土体压缩指数 $C_{c}$ 等对m值的影响作用；经统计分析建立了m值与 $Y_{0}$ , $C_{c}$ 间的拟合关系式,并以现场水平静载试验对其进行校核验证。结果表明：m值随H, $Y_{0}$ 和 $C_{c}$ 的增大而减小,且衰减速度不断减小；桩径D对m值有一定影响,现有桩径水平中D=1.25 m最佳；现场试验修正后的m值拟合关系计算可靠,且能依据土体变形参数精细化取值。
- 软土地区 /
- 桩基 /
- m值 /
- 精细化取值 /
- 拟合关系式
Abstract: The m method is a common method to analyze the deformation and internal force of laterally loaded piles. In the absence of test piles, the ratio coefficient m value of lateral resistance coefficient in the m method can only be taken from a wide range recommended by the relevant code according to the type of foundation soil, etc., highly dependent on engineering experience and random. Main soft soils along Shanghai-Nantong Railway are classified into 11 subcategories according to the compression characteristics. The influences of horizontal force H, horizontal displacement $Y_{0}$ of mud surface (pile top), pile diameter D and soil compression index $C_{c}$ on m value are analyzed through the numerical test method. The fitting relation between m and $C_{c}$ and the relation between m and $Y_{0}$ are established through statistical analysis, and are verified by the field horizontal static load tests. The results show that the m value decreases with H, $Y_{0}$ and $C_{c}$ , and the attenuation speed decreases continuously. D has a certain influence on the m value, corresponding to the best diameter of pile D=1.25 m. The fitting formula for m value corrected by the field tests is reliable and can be fine-tuned according to the deformation parameters of soils.
- soft soil area /
- pile foundation /
- m value /
- refined value /
- fitting formula

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图 1 地层概化

Figure 1. Stratigraphic generalization

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图 2 有限元模型

Figure 2. Finite element model

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图 3 土样压缩系数 $C_{c}$ 与压缩指数 $a_{v}$ 关系

Figure 3. Relationship between compression coefficient $C_{c}$ of soil samples and compression index $a_{v}$

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图 4 数值模拟结果(D=1.25 m)

Figure 4. Results of numerical simulation (D=1.25 m)

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图 5 桩径D与m值关系

Figure 5. Relationship between pile diameter D and m value

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图 6 压缩指数 $C_{c}$ 与m值关系

Figure 6. Relationship between compression index of soil $C_{c}$ and m value

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图 7 单桩水平静载现场试验

Figure 7. Horizontal static load field tests on single pile

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图 8 现场试验结果

Figure 8. Results of field tests

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图 9 土体压缩指数 $C_{c}$ 与m值关系

Figure 9. Relationship between compression index of soil $C_{c}$ and m value

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图 10 系数a, b与 $Y_{0}$ 关系

Figure 10. Relationship among coefficient a, b and $Y_{0}$

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图 11 m值拟合关系式修正

Figure 11. Correction of modified formula for m value

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图 12 m值拟合关系式验证

Figure 12. Verification of modified formula for m value

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表 1 沿线主要软土亚类划分

Table 1 Classification of main soft soil subclasses along line

材料编号	压缩系数 $a_{v}$ /MPa^-1	压缩指数 $C_{c}$	压缩参数λ	回弹参数k
Mat1	0.280	0.102	0.044	0.0044
Mat2	0.455	0.158	0.069	0.0069
Mat3	0.630	0.214	0.093	0.0093
Mat4	0.805	0.270	0.117	0.0117
Mat5	0.980	0.326	0.142	0.0142
Mat6	1.155	0.381	0.166	0.0166
Mat7	1.330	0.437	0.190	0.0190
Mat8	1.505	0.493	0.214	0.0214
Mat9	1.680	0.549	0.239	0.0239
Mat10	1.855	0.605	0.263	0.0263
Mat11	2.030	0.661	0.287	0.0287

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表 2 修正剑桥模型参数（软土）

Table 2 Material parameters for MCC (soft soil)

材料	重度 $γ$ /(kN·m^-3)	初始孔隙比 $e_{0}$	CSL斜率M	压缩参数 $λ$
黏土	18.5	1.07	0.566	0.044~0.287

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表 3 中砂与桩基物理力学参数

Table 3 Physico-mechanical parameters of medium sand and pile foundation

材料	重度 $γ$ /(kN·m^-3)	模量E/MPa	泊松比 $ν$	摩擦角 $φ$ /(°)
中砂	20.5	36	0.25	35
桩基	24.0	30000	0.20	—

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表 4 桩顶水平位移系数 $v_{y}$ 取值

Table 4 Values of coefficient of horizontal displacement of pile top $v_{y}$

$α h$	≥4.0	3.5	3.0	2.8	2.6	2.4
$v_{y}$	2.441	2.502	2.727	2.905	3.163	3.526

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