盐湖区高速铁路长短桩复合地基变形特性

杨晓华; 王东清; 张莎莎; 孔祥鑫; 李安洪; 赵彦虎

doi:10.19818/j.cnki.1671-1637.2024.03.012

盐湖区高速铁路长短桩复合地基变形特性

doi: 10.19818/j.cnki.1671-1637.2024.03.012

1.
长安大学公路学院，陕西西安 710064
2.
中铁二院工程集团有限责任公司，四川成都 610031

基金项目:

国家自然科学基金项目 42101126

陕西省自然科学基础研究计划 2019JM-147

中国中铁股份有限公司科技研究开发计划 2017-major-11-04

详细信息

作者简介:
杨晓华(1961-)，男，河北唐山人，长安大学教授，工学博士，从事岩土与隧道工程研究

中图分类号: U213.15
计量
- 文章访问数: 96
- HTML全文浏览量: 29
- PDF下载量: 24
- 被引次数: 0
出版历程
- 收稿日期: 2024-01-21
- 网络出版日期: 2024-07-18
- 刊出日期: 2024-06-30

Deformation characteristics of long-short pile composite foundation for high-speed railway in salt lake region

1.
School of Highway, Chang'an University, Xi'an 710064, Shaanxi, China
2.
China Railway Eryuan Engineering Group Co., Ltd., Chengdu 610031, Sichuan, China

Funds:

National Natural Science Foundation of China 42101126

Natural Science Basic Research Plan in Shaanxi Province of China 2019JM-147

Science and Technology Development Project of China Railway Group Limited 2017-major-11-04

More Information

Author Bio:
YANG Xiao-hua(1961-), male, professor, PhD, xiaohuay@126.com

摘要

摘要: 依托伊朗德黑兰至伊斯法罕高速铁路项目，开展全长桩(混凝土桩)、全短桩(碎石桩)和长短桩(混凝土桩-碎石桩)复合地基离心模型试验，模拟了填筑与工后2年的地基沉降过程，研究了桩长比、桩间距、短桩布置形式与填土高度对地基沉降特性的影响。研究结果表明：在相同地质条件下，全长桩、长短桩和全短桩复合地基的桩间土工后沉降分别为28.16、36.17和53.95 mm，分别减小了70%、60%和40%以上，因此，全长桩和长短桩复合地基工后沉降可以满足规范要求(不超过于50 mm)，长短桩复合地基工后沉降介于全长桩和全短桩复合地基工后沉降之间；桩长比每增加0.1，桩间距分别为3、4倍桩径时长短桩复合地基沉降分别减小7%~12%和8%左右，表明提高桩长比能够显著改善复合地基的沉降控制效果，并随桩间距的增大而更为有效；桩间距从3倍桩径增大到5倍桩径，桩长比为0.5时复合地基沉降从36.56 mm增至55.71 mm，桩长比为0.7时复合地基沉降从28.38 mm增至45.93 mm，表明在较大桩间距下沉降控制效果较差，为使沉降满足规范要求，桩间距为5倍桩径时桩长比应不小于0.5；桩长比为0.7时，一长一短、一长两短和一长三短3种布置形式复合地基沉降分别为28.37、38.06和43.69 mm，表明在相邻两长桩之间布置更多短桩可以兼顾沉降控制与经济性，短桩布置越多，长桩应力越大，但应力整体趋势保持不变；不同填土高度下长短桩复合地基中碎石桩块体以向下运动为主，长桩刺入垫层，短桩刺入软土，并在剪切变形与块体侧向挤出的作用下形成局部潜在滑移面。
- 高速铁路 /
- 路基工程 /
- 长短桩复合地基 /
- 软弱盐渍土 /
- 沉降 /
- 离心模型试验 /
- 数值模拟
Abstract: Based on the Tehran-Isfahan high-speed railway project in Iran, centrifuge model tests were conducted for full-length pile (concrete pile) composite foundation, full-short pile (gravel pile) composite foundation, and long-short pile (concrete pile-gravel pile) composite foundation, their settlement processes were simulated in embankment construction and following two years, and the effects of pile length ratio, pile spacing, short pile layout and filling height on the settlement characteristics were studied. Research results show that under the same geological condition, the post-construction settlements of the soils between piles for full-length, long-short, and full-short pile composite foundations are 28.16, 36.17, and 53.95 mm and reduce by over 70%, 60%, and 40%. Therefore, the post-construction settlements for full-length and long-short pile composite foundations meet the regulatory requirement of no more than 50 mm, and the post-construction settlement of long-short pile composite foundation is between the settlements of full-length and full-short pile composite foundations. For long-short pile composite foundation, increasing pile length ratio by 0.1 may reduce settlement by 7%-12% for the pile spacing of 3 times pile diameter and around 8% for the pile spacing of 4 times pile diameter, indicating that increasing pile length ratio can significantly improves settlement control, and the control is more effective as pile spacing increases. When the pile spacing increases from 3 times pile diameter to 5 times pile diameter, composite foundation settlement increases from 36.56 mm to 55.71 mm for a pile length ratio of 0.5, and from 28.38 mm to 45.93 mm for a pile length ratio of 0.7, indicating that settlement control is less effective at larger pile spacing. To meet the regulatory settlement requirement, the pile length ratio should not be less than 0.5 when the pile spacing is 5 times pile diameter. For a pile length ratio of 0.7, composite foundations settlements with one long-one short, one long-two short, and one long-three short pile arrangements are 28.37, 38.06, and 43.69 mm, indicating that placing more short piles between adjacent long piles can balance settlement control and economic efficiency. As the number of short piles increases, the stress on the long piles increases, but the stress distribution trend remains unchanged. Under different filling heights, in long-short pile composite foundation, gravel piles primarily move downward, long piles penetrate cushion layer, short piles penetrate soft soil, and localized potential slip surfaces form due to shear deformation and lateral extrusion of gravel piles.
- high-speed railway /
- subgrade engineering /
- long-short pile composite foundation /
- weak saline soil /
- settlement /
- centrifugal model test /
- numerical simulation

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图 1 盐湖地质

Figure 1. Salt lake geology

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图 2 试验设备

Figure 2. Test equipments

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图 3 试验模型(单位：mm)

Figure 3. Test model (unit: mm)

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图 4 地基模型

Figure 4. Foundation models

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图 5 复合地基累计沉降曲线

Figure 5. Cumulative settlement curves of composite foundations

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图 6 复合地基桩土应力比

Figure 6. Pile-soil stress ratios in composite foundations

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图 7 复合地基模型与接触面类型

Figure 7. Composite foundation model and contact surface types

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图 8 离心模型试验数据与数值计算结果对比

Figure 8. Comparison of centrifugal model test data and numerical calculation results

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图 9 短桩桩长对复合地基沉降的影响

Figure 9. Influence of short pile length on settlements of composite foundations

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图 10 桩长比对长桩应力的影响

Figure 10. Influence of pile length ratio on long pile stress

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图 11 桩间距对复合地基沉降的影响

Figure 11. Influence of pile spacing on settlements of composite foundations

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图 12 桩间距对长桩应力的影响

Figure 12. Influence of pile spacing on long pile stress

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图 13 短桩布置形式

Figure 13. Arrangements of short piles

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图 14 不同短桩布置形式的复合地基沉降

Figure 14. Settlements of composite foundations with different short piles arrangements

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图 15 不同短桩布置形式的长桩应力

Figure 15. Long pile stresses under different short piles arrangements

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图 16 连续-非连续计算模型

Figure 16. Continuous-discontinuous calculation model

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图 17 不同填土高度复合地基沉降

Figure 17. Settlements of composite foundations with different filling heights

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图 18 填土高度为3.5和5.0 m复合地基剪应变增量

Figure 18. Shear strain increments of composite foundations with filling heights of 3.5 and 5.0 m

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表 1 盐湖区地基土物理力学参数

Table 1. Physical and mechanical parameters of foundation soils in salt lake region

断面土层	天然密度/(g·cm^-3 )	黏聚力/kPa	内摩擦角/(°)	压缩模量/MPa	压缩系数	泊松比
盐渍化松软土	1.60	13	15	3	0.46	0.33
盐渍化黏土	1.70	28	23	8	0.19	0.33

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表 2 模型地基土物理力学参数

Table 2. Physical and mechanical parameters of model foundation soils

断面土层	含水率/%	密度/(g·cm^-3 )	黏聚力/kPa	内摩擦角/(°)
盐渍化松软土	24.2	1.61	11.5	14.4
盐渍化黏土	8.6	1.78	20.1	23.6

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表 3 离心模型试验物理量的相似比

Table 3. Similarity ratios of physical quantities in centrifugal model tests

物理量	相似比	物理量	相似比
长度	1/n	弹性模量	1
重度	n	加速度	n
黏聚力	1	应力	1
内摩擦角	1	位移	1/n

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表 4 离心模型试验加速方案

Table 4. Acceleration scheme in centrifugal model tests

试验阶段	填土高度/m	加速度/g	模型历时/min	原型历时/d
模型预压		10.0	5.0	1
填土过程	2	29.1	51.2	30
	4	60.5	11.8	30
	5	80.0	6.8	30
工后1年	5	80.0	82.2	365
工后2年	5	80.0	82.2	365

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表 5 地基处理方案

Table 5. Foundation treatment schemes

复合地基形式		长度/m	尺寸/m	桩间距/m	置换率	布桩形式
全长桩复合地基		22	0.45×0.45	1.35	0.088
全短桩复合地基		11	0.50	1.35	0.088
长短桩复合地基	长桩	22	0.45×0.45	1.35	0.044
长短桩复合地基	短桩	11	0.50	1.35	0.044

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表 6 地基结构的数值计算参数

Table 6. Numerical calculation parameters of foundation structures

地基结构	天然密度/(g·cm^-3 )	黏聚力/kPa	内摩擦角/(°)	泊松比	压缩模量/MPa	弹性模/MPa	渗透系数/(m·s^-1)
垫层	2.1	5	30	0.33	30		1.2×10^-4
路堤填方	2.1	15	27	0.33	25
盐渍化松软土	1.6	13	15	0.33	3		2.7×10^-7
盐渍化黏土	1.7	28	23	0.33	8		4.3×10^-7
预制桩	2.1			0.20		3.5×10⁴
碎石桩	2.0	0	38	0.25		70.0	1.7×10^-3

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表 7 碎石桩参数

Table 7. Parameters of gravel pile

接触杨氏模量/GPa	接触刚度比	接触摩擦因数	密实度	块体重度/(kN·m^-3)
2.0	2.0	0.55	0.8	25

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