竖向荷载作用下螺杆灌注桩受压承载机理的试验研究

王曙光; 冯浙; 唐建中; 赵志鹏

doi:10.11779/CJGE202102019

竖向荷载作用下螺杆灌注桩受压承载机理的试验研究 English Version

王曙光^{1, 2,},
冯浙³,
唐建中¹,
赵志鹏¹

1.
中国建筑科学研究院地基基础研究所,北京100013
2.
住房和城乡建设部防灾研究中心,北京100013
3.
国网四川省电力公司建设分公司,四川　成都　610052

详细信息

作者简介:
王曙光（1972— ）,男,工学博士,研究员,主要从事上部结构地基基础共同作用、基坑支护、地基处理等方面的研究工作。E-mail：wshgcabr@aliyun.com

中图分类号: TU43
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出版历程
- 收稿日期: 2020-05-25
- 网络出版日期: 2022-12-04
- 刊出日期: 2021-01-31

Experimental study on bearing mechanism of screw cast-in-place piles under vertical loads

1.
Institute of Foundation Engineering, China Academy of Building Research, Beijing 100013, China
2.
Disaster Prevention Research Center, Ministry of Housing and Urban-Rural Development, Beijing 100013, China
3.
State Grid Sichuan Construction Company, Chengdu 610052, China

摘要

摘要: 螺杆灌注桩是一种上部为圆柱形、下部为螺丝形的组合式灌注桩,由于具有承载力高、节约材料、文明施工程度高等特点,在工程中得到广泛应用。螺杆灌注桩由于其特有的施工工艺及截面形式,使得其承载机理不同于等截面灌注桩。通过室内模型试验,采用图像处理技术直观地得到螺杆桩和直杆桩的破坏形态,进而对其承载机理和承载力计算进行探讨,并采用现场试验进行验证。模型试验和现场试验表明,螺杆桩的单桩承载力高于同直径的等截面桩,螺纹段的侧阻力与等截面桩的侧阻力相比明显提高。螺纹段和直杆段的极限侧阻力产生机理有所不同。对于螺纹段,在极限状态下,由于螺牙的机械咬合作用使得螺牙以及螺牙之间的土体作为整体与周边土体产生剪切位移,螺纹段的极限侧阻力表现为周边土体的抗剪强度,破坏面为连续的拱形,拱形截面的平均直径大于螺牙的外径；对于直杆桩,在极限状态下,侧阻力表现为桩体与桩周土体的摩擦阻力,破坏面为桩周的圆柱面。根据试验结果,给出螺杆灌注桩单桩极限承载力的表达式,并给出相关参数的取值建议。
- 螺杆灌注桩 /
- 变形形态 /
- 竖向承载机理 /
- 模型试验 /
- 现场试验
Abstract: The screw cast-in-place pile is a kind of variable-section cast-in-place pile with cylindrical top and threaded bottom. Due to its special construction technology and section form, the bearing mechanism of screw piles is different from that of piles with the same section. Through the indoor model tests, the failure modes of the screw piles and the straight rod piles are obtained intuitively by using the image processing technology, and then the bearing mechanism and the calculation of the bearing capacity are discussed, and the field tests are used for verifiction. The model and field tests show that the bearing capacity of a single screw pile is higher than that of the pile with the same diameter, and the lateral resistance of the screw pile is obviously higher than that of the pile with the same diameter. The mechanism of limit lateral resistance is different between the screw segment and the straight segment. For the screw section, under the limit state, because of the teeth of mechanical interlocking between the teeth and the teeth of the soils as a whole and the shear displacement of surrounding soils, the lateral resistance is shear strength of surrounding soils, the fracture surface is continuously arch-shaped, and the average diameter of the arch section is higher than the diameter of the screw teeth. For the straight pile, under the limit state, the lateral resistance is the friction resistance between the pile body and the soils around the pile, and the failure surface is the cylinder around the pile. According to the test results, the expression for the ultimate bearing capacity of a single screw cast-in-place pile is given, and the value of the relevant parameters are suggested.
- screw cast-in-place pile /
- displacement feature /
- vertical bearing mechanism /
- model test /
- field test

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图 1 模型桩详图

Figure 1. Schematic diagram of model piles

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图 2 砂箱及加载装置

Figure 2. Sand box and loading devices

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图 3 模型桩的荷载沉降曲线

Figure 3. Load settlement curves of model piles

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图 4 模型桩的平均侧阻力和平均端阻力曲线

Figure 4. Average lateral and terminal resistances of model piles

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图 5 模型桩桩周土体位移场

Figure 5. Displacement fields of soils around model piles

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图 6 模型桩的极限破坏形态

Figure 6. Ultimate failure modes of model piles

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图 7 工程地质剖面

Figure 7. Geological prospecting section

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图 8 螺杆灌注桩详图

Figure 8. Schematic diagram of screw cast-in-place piles

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图 9 试验桩的荷载沉降曲线

Figure 9. Load-settlement curves of test piles

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图 10 试验桩轴力分布图

Figure 10. Axial forces of test piles

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图 11 试验桩侧阻力分布图

Figure 11. Lateral resistance diagram of test piles

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表 1 模型桩参数

Table 1 Parameters of model piles (mm)

桩型	桩长	外径	内径	螺距	螺牙宽度	螺牙厚度
螺杆桩	400	40	30	50	5	2
直杆桩	400	40	—	—	—	—

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表 2 土性指标

Table 2 Property indices of soils

岩土名称	天然重度 $γ$ /(kN·m^-3)	天然含水率w/%	孔隙比e	塑性指数I_P	液性指数I_L	压缩模量 E_s /MPa	压缩系数 $α_{1 \sim 2}$ /(MPa^-1)	黏聚力c/ kPa	内摩擦角φ/(°)	承载力特征值 f_ak / kPa
素填土①	17.0	—	—	—	—	3.0	—	10	8	80
粉质黏土③-2	19.5	26.47	0.767	14.3	0.41	5.5	0.27	25	15	120
含碎石粉质黏土④	19.0	27.66	0.796	16.2	0.38	6.0	0.26	30	18	160
含粉质黏土碎石⑨	21.5	—	—	—	—	30.0	—	8	35	380
昔格达组粉砂岩⑩	19.0	—	—	—	—	15.0	—	30	26	260

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表 3 试验桩的参数

Table 3 Specific parameters of test piles

桩号	桩长/m	直杆段桩长/m	螺纹段桩长/m	外径/mm	内径/mm	螺距/mm
1	10	10	—	600	—	—
3	10	3	7	600	540	500

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