强震作用下近断层桥梁桩基动力响应

冯忠居; 张聪; 何静斌; 关云辉; 袁枫斌

doi:10.19818/j.cnki.1671-1637.2022.04.012

强震作用下近断层桥梁桩基动力响应

doi: 10.19818/j.cnki.1671-1637.2022.04.012

1.
长安大学公路学院，陕西西安 710064
2.
中国电力建设集团有限公司西北勘测设计研究院有限公司，陕西西安 710064
3.
陕西建工机械施工集团有限公司，陕西西安 710064
4.
北京建达道桥咨询有限公司，北京 102308

基金项目:

国家自然科学基金项目 51708040

海南省交通科技项目 HNZXY2015-045R

详细信息

作者简介:
冯忠居(1965-)，男，山西万荣人，长安大学教授，工学博士，从事桥梁桩基与岩土工程研究

通讯作者:
张聪(1994-)，男，河南焦作人，长安大学工学博士研究生

中图分类号: U443.1
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- 被引次数: 0
出版历程
- 收稿日期: 2022-02-21
- 网络出版日期: 2022-10-08
- 刊出日期: 2022-08-25

Dynamic response of bridge pile foundation near fault under strong earthquake

1.
School of Highway, Chang'an University, Xi'an 710064, Shaanxi, China
2.
Northwest Engineering Co., Ltd., Power China, Xi'an 710064, Shaanxi, China
3.
SCEGC Mechanized Construction Group Co., Ltd., Xi'an 710064, Shaanxi, China
4.
Beijing JianDa Road and Bridge Consulting Co., Ltd., Beijing 102308, China

Funds:

National Natural Science Foundation of China 51708040

Hainan Transportation Technology Project HNZXY2015-045R

More Information

Author Bio:
FENG Zhong-ju(1965-), male, professor, PhD, ysf@gl.chd.edu.cn

ZHANG Cong(1994-), male, doctoral student, zhangcong@chd.edu.cn

摘要

摘要: 为探明强震作用下断层上、下盘桥梁桩基动力响应差异，依托海南省海文大桥工程，通过振动台模型试验，研究了0.15g~0.60g地震动强度作用下断层上、下盘桩基的桩身加速度、桩顶相对位移、桩身弯矩响应规律差异与桩基损伤特征。研究结果表明：在不同地震动强度作用下，断层上、下盘桩基的桩顶加速度峰值相差0.291~0.488 m·s^-2，桩顶加速度放大系数相差0.067~0.195，原因为断层对两侧岩土体影响范围存在差异与桩周岩土体“非线性”差异；随着地震动强度的增大，断层上、下盘桩基的桩顶相对位移差值逐渐增大，最大差值为0.77 mm；断层上、下盘桩基的弯矩最大值相差5.294~82.932 kN·m，且弯矩最大值均出现在覆盖层软硬土交界面与基岩面附近，原因在于下盘作为稳定盘，受上盘土体挤压作用，对下盘岩土体的振动剪切有一定抑制作用；地震动强度为0.35g时，断层上、下盘桩的最大弯矩均未超过抗弯承载力，满足海文大桥抗震设防烈度Ⅷ度(0.35g)的要求；地震动强度为0.35g~0.45g时，断层上盘桩的基频变化幅度较小，地震动强度为0.50g~0.60g时，断层上盘桩的基频显著降低，在桩顶与承台连接处、软硬土层界面与基岩面附近出现裂缝，说明此时桩基已发生损伤。可见，断层上盘桩基的桩身加速度峰值、桩顶相对位移与桩身弯矩动力响应指标均大于下盘桩基，断层上、下盘桩基动力响应变化规律差异显著，体现出显著的“断层上盘效应”，因此，强震作用下近断层桥梁桩基础抗震设计时，应着重考虑断层上盘桩基础的抗震承载能力。
- 桥梁工程 /
- 桩基础 /
- 振动台试验 /
- 强震 /
- 断层破裂带 /
- 动力响应
Abstract: In order to find out the difference in the dynamic responses of bridge piles on the hanging wall and footwall of the fault under a strong earthquake, relying on the Haiwen Bridge project in Hainan Province, the shaking table model test was carried out to study the response differences of pile acceleration, pile top relative displacement and pile bending moment response laws, and the piles damage characteristics on the hanging wall and footwall of the fault under the action of 0.15g-0.60g ground motion intensity. Research result shows that the difference between pile top peak accelerations on the hanging wall and footwall of the fault is 0.291-0.488 m·s^-2, and the difference in the amplification factor of pile top acceleration is 0.067-0.195 under the different ground motion intensities. The reason is the difference in the influence range of the fault on the rock and soil mass on both sides and the "non-linear" difference of the rock and soil mass around the pile. With the increase of earthquake intensity, the difference between the pile top relative displacements on the hanging wall and footwall of the fault increases gradually, and the maximum difference is 0.77 mm. The difference between the maximum bending moments of the pile foundations on the hanging wall and footwall of the fault is 5.294-82.932 kN·m, and the maximum bending moment occurs at the interface of soft and hard soil and near the bedrock surface. The reason is that the footwall, as a stable plate, is squeezed by the soil mass of the hanging wall, which has a certain inhibitory effect on the vibration and shear of the rock and soil mass of the footwall. When the ground motion strength is 0.35g, the maximum bending moment of the pile on the hanging wall and footwall of the fault does not exceed the bending bearing capacity, which meets the requirement of seismic fortification intensity Ⅷ of Haiwen Bridge(0.35g). When the ground motion intensity is 0.35g-0.45g, the pile fundamental frequency on the hanging wall of the fault has a small variation range. When the ground motion intensity is 0.50g-0.60g, the pile foundation frequency on the hanging wall decreases significantly. The cracks appear at the connection between the pile top and cap, the interface between the soft and hard soil layer, and the bedrock surface, which shows that the piles have been damaged. In summary, the acceleration of pile, the relative displacement of pile top, and the bending moment of pile on the hanging wall are larger than those on the footwall. The dynamic response changes of the piles on the hanging wall and footwall of the fault are significantly different, which shows significant "the hanging wall effect of fault". Therefore, in the seismic design of bridge pile foundation near the fault under strong earthquake, the seismic capacity of hanging wall pile foundation should be considered.
- bridge engineering /
- pile foundation /
- shaking table test /
- strong earthquake /
- fault fracture zone /
- dynamic response

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图 1 桩基础与断层相对位置

Figure 1. Relative position of pile foundation and fault

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图 2 叠层剪切式模型箱

Figure 2. Laminated shear model box

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图 3 土体剪切波速测试

Figure 3. Shear wave velocity test of soil

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图 4 模型桩

Figure 4. Model pile

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图 5 模型桩布置

Figure 5. Layout of model piles

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图 6 0.35g-5010波

Figure 6. 0.35g-5010 wave

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图 7 不同强度地震动作用下桩身加速度峰值

Figure 7. Peak accelerations of piles under ground motions with different intensities

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图 8 桩顶加速度峰值与放大系数

Figure 8. Peak acceleration and amplification factors of pile tops

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图 9 桩顶相对位移变化规律

Figure 9. Variation laws of relative displacements at pile tops

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图 10 桩身弯矩峰值变化规律

Figure 10. Variation laws of peak bending moments of piles

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图 11 桩身弯矩最大值

Figure 11. Maximum bending moments of piles

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图 12 抗弯承载能力安全度

Figure 12. Safety degrees of flexural bearing capacity

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图 13 断层上盘桩(38-1^#)傅里叶谱

Figure 13. Fourier spectrums of 38-1^# pile on hanging wall of fault

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图 14 断层上盘38-1^#桩基频变化规律

Figure 14. Variation law of foundation frequency of 38-1^# pile on hanging wall of fault

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图 15 桩基损伤

Figure 15. Damage of pile foundation

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表 1 振动台技术指标

Table 1. Technical specifications of vibrating table

性能	台面尺寸/mm	振动模式	频率范围/Hz	模型载重/t	抗倾覆力矩/(kN·m)	最大加速度幅值(满载)/g		最大速度幅值/(cm·s^-1)		最大位移幅值/mm
参数	5 000×5 000	正弦、随机地震动	0.5~50	0~30	300	水平向	1.0	水平向	50	水平向	80
参数	5 000×5 000	正弦、随机地震动	0.5~50	0~30	300	纵向	0.7	纵向	40	纵向	50

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表 2 试验物理量相似常数

Table 2. Similarity constants of test physical quantities

分类	物理量	相似常数
荷载	速度	0.18
	时间	0.18
	加速度	1
	人工质量	100 kg
	重力加速度	1
几何形状	频率	5.48
	线位移	1/30
	线尺寸	1/30
材料特征	应力	1
	应变	1
	泊松比	1
	弹性模量	1

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表 3 模型土参数

Table 3. Model soil parameters

模型土	密度/(g·cm^-3)	含水率/%	压缩模量/MPa	孔隙比	黏聚力/kPa	内摩擦角/(°)
淤泥质黏土	1.67	49.8	3.78	1.32	10.2	4
砂砾	1.94	23.2	4.68	0.91	13.3	25
卵石土	2.03	31.5	24.00	0.73	8.0	39

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表 4 土体剪切波速

Table 4. Shear wave velocities of soils m·s^-1

土体		淤泥质黏土	砂砾	卵石土	微风化花岗岩/混凝土	破碎带/碎石
剪切波速	原型	136	263	526	899
剪切波速	模型	138	276	539	917	120

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表 5 模型桩参数

Table 5. Model pile parameters

桩身材料	桩长/cm	桩径/cm	桩身钢筋直径/mm	配筋率/%
C35混凝土	180	8	4	2.4

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