旋喷搅拌桩加固含易液化粉土夹层软基的现场试验

章定文; 刘涉川; 蔺文峰; 时洪斌; 毛忠良

doi:10.19818/j.cnki.1671-1637.2022.01.008

旋喷搅拌桩加固含易液化粉土夹层软基的现场试验

doi: 10.19818/j.cnki.1671-1637.2022.01.008

1.
东南大学交通学院, 江苏南京 211189
2.
中国水利水电第四工程局有限公司, 青海西宁 810007
3.
中铁第五勘察设计院集团有限公司, 北京 102600

基金项目:

国家自然科学基金项目 52078129

详细信息

作者简介:
章定文(1978-)，男，湖南常德人，东南大学教授，工学博士，从事岩土工程研究

中图分类号: U213.1
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出版历程
- 收稿日期: 2021-08-06
- 刊出日期: 2022-02-25

Field test on soft ground with liquefiable silt interlayer reinforced by jet-grouted mixing piles

1.
School of Transportation, Southeast University, Nanjing 211189, Jiangsu, China
2.
Sinohydro Engineering Bureau 4 Co., Ltd., Xining 810007, Qinghai, China
3.
China Railway Fifth Survey and Design Institute Group Co., Ltd., Beijing 102600, China

Funds:

National Natural Science Foundation of China 52078129

More Information

Author Bio:
ZHANG Ding-wen (1978-), male, professor, PhD, zhang@seu.edu.cn

摘要

摘要: 依托含易液化粉土夹层软基加固实体工程，采用现场试验的方法研究了旋喷搅拌桩加固含易液化粉土夹层软基的适用性和加固效果；通过钻孔取芯和静载试验测量分析了旋喷搅拌桩在含易液化粉土夹层软基中的成桩质量和桩芯强度；监测了路堤荷载下旋喷搅拌桩加固含易液化粉土夹层软基典型断面的施工期间及工后的地表沉降、深层水平位移、桩体荷载分担比、桩土应力比和超静孔隙水压力等数据，分析了旋喷搅拌桩加固含易液化粉土夹层软基的实际加固效果和工程受力特性。研究结果表明：旋喷搅拌桩在含易液化粉土夹层软基中可完整成桩，桩芯28 d无侧限抗压强度可达2.5 MPa，相对于常规搅拌桩强度提升了约一倍；在路堤荷载下，旋喷搅拌桩能有效地减小地基沉降和坡脚深层水平位移，并提高路堤的稳定性；旋喷搅拌桩加固地基桩土差异沉降较小，桩土应力比介于5~10，桩体荷载分担比小于50%，具有复合地基特性，复合地基分为柔性桩复合地基和刚性桩复合地基，两者设计方法差异很大，本文研究的旋喷搅拌桩建议按照柔性桩复合地基设计。可见，旋喷搅拌桩加固含易液化粉土夹层软基效果良好，可适用于实际工程。
- 岩土工程 /
- 地基处理 /
- 旋喷搅拌桩 /
- 现场试验 /
- 成桩质量 /
- 桩土应力比 /
- 复合地基
Abstract: For the engineering projects involving the reinforcement of soft ground with liquefiable silt interlayer, the applicability and effect of reinforcement using jet-grouted mixing piles were investigated on-site. The pile-forming quality and core strength of jet-grouted mixing pile were measured and analyzed by investigating the core samples obtained by drilling and static loading test. The data pertaining to ground surface settlement, deep horizontal displacement, pile load sharing ratio, pile-soil stress ratio, and excess pore water pressure were monitored under embankment load at a typical section of the soft ground during and after reinforcement. The reinforcement effect and stress characteristic on soft ground with liquefiable silt interlayer reinforced by the jet-grouted mixing piles were analyzed. Analysis results show that jet-grouted mixing piles can be successfully driven into the soft ground with liquefiable silt interlayer. The unconfined compressive strength of the pile core reaches 2.5 MPa at 28 d, which is nearly twice as high as the value of the core of conventional mixing pile. Under the embankment load, the jet-grouted mixing piles can effectively reduce the foundation settlement and the deep horizontal displacement at the toe of the slope, and improve the embankment stability. The pile-soil differential settlement is relatively small, the pile-soil stress ratio is 5-10, and the pile load sharing ratio is less than 50% in the jet-grouted mixing pile reinforced foundation, demonstrating the advantageous characteristic of the composite foundation. Composite foundation is divided into flexible pile composite foundation and rigid pile composite foundation. The design methods of the two are very different. The jet-grouted mixing piles studied in this paper is suggested to be designed as flexible pile composite foundation. Therefore, the soft ground with liquefiable silt interlayer reinforced by the jet-grouted mixing piles demonstrates satisfactory effect and can be used in practical engineering. 2 tabs, 12 figs, 30 refs.
- geotechnical engineering /
- ground improvement /
- jet-grouted mixing pile /
- field test /
- pile-forming quality /
- pile-soil stress ratio /
- composite foundation

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图 1 旋喷搅拌桩的施工设备

Figure 1. Construction equipment of jet-grouted mixing pile

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图 2 传感器埋设

Figure 2. Sensor embedding

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图 3 旋喷搅拌桩芯样

Figure 3. Core samples of jet-grouted mixing pile

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图 4 芯样无侧限抗压强度试验结果

Figure 4. Test results of unconfined compressive strengths of core samples

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图 5 旋喷搅拌桩单桩载荷试验结果

Figure 5. Load test results of single jet-grouted mixing pile

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图 6 路堤填高和地表沉降历时曲线

Figure 6. Curves of embankment height and ground surface settlement with time

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图 7 桩土差异沉降历时曲线

Figure 7. Curves of pile-soil different settlement with time

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图 8 路堤坡脚处深层水平位移

Figure 8. Deep horizontal displacements at toe of embankment slope

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图 9 不同位置处应力

Figure 9. Stresses at different positions

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图 10 不同位置桩土应力比

Figure 10. Pile-soil stress ratios at different positions

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图 11 不同位置桩体荷载分担比

Figure 11. Load share ratios of pile at different positions

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图 12 不同深度的超静孔隙水压力

Figure 12. Excess pore water pressures at different depths

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表 1 旋喷搅拌桩施工设备的技术参数

Table 1. Technical parameters of construction equipment of jet-grouted mixing pile

成桩深度/m	成桩直径/mm	钻杆动力/kW	卷扬机功率/kW	注浆泵排量/(L·min^-1)	喷射压力/MPa
0~25	500~800	55	75	125	10~25

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表 2 各土层物理力学性质指标

Table 2. Physical and mechanical properties of each soil layer

层号	土类	重度/(kN·m^-1)	土粒比重	含水率/%	孔隙比	液限/%	塑限/%	黏聚力/kPa	内摩擦角/(°)	压缩模量/MPa
1	粉土	19.6	2.70	25.8	0.780	28.0	19.8	9	27.6	10.11
2	软黏土	19.0	2.75	36.8	0.904	41.4	22.5	20	5.7	3.50
3	粉土	19.8	2.70	25.3	0.712	27.7	19.5	10	28.3	9.87
4	黏土	19.6	2.73	27.7	0.819	37.4	21.0	32	8.3	6.05
5	黏土	19.9	2.75	25.9	0.742	42.7	22.3	61	12.7	8.70

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