陀螺桩垫层加强袋装砂井排水地基现场试验

李国维; 余彦杰; 熊力; 吴建涛; 曹雪山

doi:10.11779/CJGE202103004

陀螺桩垫层加强袋装砂井排水地基现场试验 English Version

李国维^{1, 2,},
余彦杰^{1, 3},
熊力^{1, 4},
吴建涛^{1, 2, ,},
曹雪山^{1, 2}

1.
河海大学岩土力学与堤坝工程教育部重点实验室,江苏　南京　210024
2.
河海大学道路与铁道工程研究所,江苏　南京　210024
3.
浙江省电力建设有限公司,浙江　宁波　315000
4.
河海大学岩土工程科学研究所,江苏　南京　210024

基金项目:

国家自然科学基金项目 41272327

详细信息

作者简介:
李国维（1964— ）,男,博士,研究员,主要从事软基路堤变形和高边坡稳定性等方面的教学与科研工作。E-mail：lgwnj@163.com

通讯作者:
吴建涛, E-mail: jiantao.wu@hhu.edu.cn

中图分类号: TU441
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出版历程
- 收稿日期: 2020-06-14
- 网络出版日期: 2022-12-04
- 刊出日期: 2021-02-28

Field tests on top-shaped concrete block cushion-reinforced soft soil foundation drained with sand bag well

LI Guo-wei^{1, 2,},
YU Yan-jie^{1, 3},
XIONG Li^{1, 4},
WU Jiang-tao^{1, 2, ,},
CAO Xue-shan^{1, 2}

1.
Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering, Hohai University, Nanjing 210024, China
2.
Highway and Railway Research Institute, Hohai University, Nanjing 210024, China
3.
Zhejiang Electric Power Construction Company, Ningbo 315000, China
4.
Geotechnical Research Institute, Hohai University, Nanjing 210024, China

摘要

摘要: 常规袋装砂井排水的软土地基要求缓慢加荷因而占用了较多工期不利于工后沉降控制。为加快袋装砂井排水地基的加荷速率开展陀螺桩垫层加强袋装砂井排水地基现场试验。研究表明：陀螺桩垫层可以提高地基的整体稳定性,在快速加荷导致软土孔压系数 $\bar{B}$ 值大于1的条件下保持地基稳定；陀螺桩垫层降低了地基浅部高压缩性土层的压缩量,相对增大了软土层下无排水体土层的压缩量,抑制软土侧向变形的发展,降低工后沉降的速率；陀螺桩垫层降低了压缩层中的孔压峰值,使软土固结过程加快；相对于砂垫层陀螺桩垫层具有更大刚度,导致上部荷载在地基中产生的附加应力分布型式发生显著变化,使得袋装砂井排水地基的综合性状得到加强。
- 陀螺桩垫层 /
- 袋装砂井 /
- 工后沉降 /
- 孔隙水压力 /
- 数值模拟
Abstract: The soft soil foundation drained by the conventional sand bag wells requires slow loading, which occupies more construction period and is not conducive to post-construction settlement control. In order to accelerate the loading rate of the drainage foundation of sand bag wells, field tests on the top-shaped concrete blocks-reinforced drainage foundation of sand bag wells are conducted. The research shows that the top-shaped concrete blocks can improve the overall stability of the foundation, and keep the foundation stable under the condition that the rapid loading causes the value of the pore pressure coefficient $\bar{B}$ of soft soil to be greater than 1. The top-shaped concrete blocks reduce the high-compressibility soil in the shallow part of the foundation. The compression of the layer relatively increases the compression of the undrained soil layer under the soft soil layer, inhibits the development of lateral deformation of the soft soil, and reduces the rate of post-construction settlement. The top-shaped concrete block layer reduces the pore pressure in the compression layer, and the peak value accelerates the consolidation process of soft soil. The top-shaped concrete blocks have greater rigidity than the sand cushions, resulting in a significant change in the type of additional stress distribution generated by the upper load in the foundation, leading to that the comprehensive behavior of the drainage sandbag ground is strengthened.
- top-shaped concrete block cushion /
- sand bag well /
- post-construction settlement /
- porewater pressure /
- numerical simulation

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图 1 铺设陀螺桩混凝土块

Figure 1. Laying top-shaped concrete blocks

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图 2 仪器埋设布置图

Figure 2. Layout of instrument embedment

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图 3 地基沉降时间曲线

Figure 3. Settlement-time curve of foundation

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图 4 双曲线法推算最终沉降量

Figure 4. Hyperbolic method for calculating final settlement

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图 5 路基中深度6 m处实测孔压时间曲线

Figure 5. Curve of measured pore pressure at a depth of 6 m in roadbed

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图 6 深层位移曲线

Figure 6. Curve of deep displacement

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图 7 模型视图

Figure 7. Model view

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图 8 模型剖面图

Figure 8. Model section

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图 9 路中地基0~18 m土层模拟沉降时间过程

Figure 9. Time histories of simulated settlement of soil layer of 0~18 m in foundation of road

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图 10 路中地基深度6 m处模拟孔压时间过程

Figure 10. Time histories of simulated pore pressure at depth of 6 m

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图 11 有无陀螺桩的路基边缘水平位移-深度的对比曲线

Figure 11. Comparative curves of horizontal displacement-depth of subgrade edge with or without top-shaped concrete block pile

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表 1 土层物理力学性质指标

Table 1 Physical and mechanical properties of soil

地层名称		层厚/m	含水率/%	密度/(g·cm^-3)	孔隙比	液限/%	塑限/%	压缩系数/MPa^-1	压缩模量/MPa	q_c/MPa	f_s/kPa	黏聚力c₀/kPa	内摩擦角 $φ_{0}$ /(°)
①	淤泥质土	3.7	55	1.56	1.7	58	41	1.25	2.15	0.22	6.0	8.4	11
②	淤泥质土	4.0	52	1.70	1.4	62	45	0.76	3.12	0.45	14.4	11.4	16
③	淤泥质细砂	7.7	22	2.06	0.6	—	—	0.13	12.12	2.65	34.5	—	32
④	粉质黏土	4.6	35	1.82	0.9	43	30	0.21	8.85	1.85	40.7	12.8	18

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表 2 软土地基加固方案参数汇总表

Table 2 Parameters of soft soil foundation reinforcement program

加固措施	直径/mm	间距/m	深度位置/m	材料属性	布置方式
袋装砂井	70	1.3	10	聚丙烯编织布	正三角形
砂垫层	中粗砂	—	0.6	2.3×10^-3 cm/d	等厚
陀螺桩	500	0.5	0.5	C30砼	正方形
桩顶系筋	12	0.5	桩顶面	HRB400	正方形网格
桩身系筋	横筋20纵筋14	0.5	桩顶下0.25	HRB400	正方形网格

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表 3 原位试验方案汇总表

Table 3 Summary of test plan

序号	材料仪器	测点深度/m	仪器型号	量程	精度	测点土层
1	沉降计	8	CJ-1000	1000 mm	±0.1 mm	淤泥土
2	沉降计	18	CJ-1000	1000 mm	±0.1 mm	粉质黏土
3	孔压计	4	JMZX-55XXHAT	200 kPa	±0.1 kPa	淤泥土
4	孔压计	6	JMZX-55XXHAT	200 kPa	±0.1 kPa	淤泥土
5	测斜管	0~15	JMZX7000	偏离垂直±30°	±0.1mm/m	淤泥土砂土粉质黏土

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表 4 沉降观测数据分析汇总表

Table 4 Analysis of observed data of settlement

观测时间/d	累计填土厚度/m	左路肩地基土0~18 m		路中地基土0~18 m		路中地基土0~8 m
观测时间/d	累计填土厚度/m	累计压缩量/mm	沉降速率/(mm·d^-1)	累计压缩量/mm	沉降速率/(mm·d^-1)	累计压缩量/mm	沉降速率/(mm·d^-1)
0~23	0	0.5	0.02	0.2	0.01	0.2	0.01
24~42	0.5	1.4	0.05	6.9	0.38	31.0	1.71
43~62	2.5	78.9	4.07	105.0	5.16	116.3	4.27
63~81	3.0	112.9	1.88	153.7	2.70	178.6	3.46
82~145	3.5	135.9	0.37	182.9	0.46	200.4	0.34
146~163	4.5	149.4	0.79	198.3	0.91	219.6	1.13
164~260	5.5	243.6	0.98	362.2	1.71	337.7	1.23

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表 5 地基沉降双曲线经验模型参数和固结度

Table 5 Parameters and consolidation degrees of hyperbolic empirical model for foundation settlement

测点位置/ 压缩层范围	双曲线模型参数		S_t=168d/mm	S_t=260d/mm	S_∞/mm	U_t=260d _/%	工后沉降/mm
测点位置/ 压缩层范围	α	β	S_t=168d/mm	S_t=260d/mm	S_∞/mm	U_t=260d _/%	工后沉降/mm
路基中/0~18 m	0.0993	0.0055	209	362	391	93	29
路基中/0~8 m	0.1070	0.0078	223	338	351	96	13
路基中/8~18 m	—	—	—	24	40	61	16

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表 6 超静孔隙水压力观测数据分析汇总表

Table 6 Analysis of observed data of excess-static pore water pressure

观测时间/d		填土高度/m	荷载增量/kPa	孔压 $u$ /kPa	$Δ u$ /kPa	$\bar{B} = \frac{Δ u}{Δ σ_{1}}$	速率/(kPa·d^-1)
观测时间/d		填土高度/m	荷载增量/kPa	孔压 $u$ /kPa	$Δ u$ /kPa	$\bar{B} = \frac{Δ u}{Δ σ_{1}}$	荷载	孔压
⑴	0~42	0.5	8.75	2.3	2.3	0.26	0.21	0.05
⑵	43~62	2.5	35.0	27.9	25.6	0.73	1.84	1.34
⑶	63~81	3.0	8.75	18.5	-9.4	-1.07	0.49	-0.52
⑷	82~145	3.5	8.75	4.3	-14.2	-1.62	0.14	-0.23
⑸	146~163	4.5	17.5	23.4	19.1	1.09	1.02	1.12
⑹	164~168	5.5	17.5	36.4	13.0	0.74	4.38	3.25
⑺	168~260	5.5	0	9.6	-26.8	—	0.00	-0.29

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表 7 模拟与实测累计沉降量对比表

Table 7 Comparison of simulated and measured progressive Accumulated settlements

测点位置	0~145 d累计沉降/mm		0~260 d累计沉降/mm
测点位置	实测值	模拟值	实测值	模拟值
路基中0~8 m	182.9	197.8	337.7	332.5
路中0~18 m	200.4	209.9	362.2	358.5
路肩0~18 m	136.9	150.3	243.6	248.3

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表 8 模拟与实测最大孔隙水压力对比表

Table 8 Comparison between simulated and measured maximum pore water pressures

测点位置/深度	0~14 5d最大孔压/kPa		145~260 d最大孔压/kPa
测点位置/深度	模拟值	实测值	模拟值	实测值
路基中心/6 m	25.93	27.92	35.92	36.40

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表 9 数值模型采用的等效力学参数

Table 9 Equivalent mechanical parameters used in numerical model

材料	ρ/(g·cm^-3)	c/kPa	φ/(°)	E/MPa	$ν$	k/(m·d^-1)	k/(cm·s^-1)
填土	1.75	15.0	20	20.0	0.22	4.3×10^-4	4.98×10^-6
碎石	2.30	0.1	40	4.5	0.30	15	1.7×10^-2
淤泥质土①	1.56	8.0	11	2.7	0.33	9.53×10^-5	1.1×10^-7
淤泥质土②	1.70	11.0	16	5.8	0.28	1.43×10^-4	1.7×10^-7
淤泥质细砂	1.80	0.1	32	12.2	0.25	4.32×10^-2	5.0×10^-5
粉质黏土	1.90	13.0	18	8.6	0.25	8.01×10^-4	9.3×10^-7
砂井	2.12	5.0	30	1.2	0.25	20	2.3×10^-2
钢筋	7.80	—	—	2×10⁵	0.31	—	—
陀螺桩	2.40	—	—	3×10⁴	0.30	—	—

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表 10 累计沉降对比表

Table 10 Comparison of cumulative settlements

压缩层范围	0~145 d累计沉降/mm			0~260 d累计沉降/mm
压缩层范围	陀螺桩S_a	砂垫层S_b	S_a/S_b	陀螺桩S_a	砂垫层S_b	S_a/S_b
路基中0~18 m	209.9	357.7	0.58	358.5	616.6	0.58
路基中0~8 m	197.8	347.0	0.57	332.5	598.0	0.56
路基中8~18 m	12.1	10.7	1.13	26.0	18.6	1.40

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表 11 路中地基深度6 m处模拟孔压特征值

Table 11 Characteristic values of simulated pore pressure at depth of 6 m

模拟过程时段/d		荷载增量 $Δ σ_{1}$ /kPa	陀螺桩孔压峰值		砂垫层孔压峰值		$\frac{u_{a}}{u_{b}}$	$\bar{B} = \frac{Δ u}{Δ σ_{1}}$		路基塑性区贯通状态
模拟过程时段/d		荷载增量 $Δ σ_{1}$ /kPa	$u_{a}$ /kPa	$Δ u_{a}$ /kPa	$u_{b}$ /kPa	$Δ u_{b}$ /kPa	$\frac{u_{a}}{u_{b}}$	陀螺桩	砂垫层	陀螺桩	砂垫层
⑵	43~63	35.0	27.9	24.8	32.9	29.9	0.85	0.71	0.85	无	无
⑸	146~163	17.5	23.1	20.1	25.8	24.1	0.90	1.14	1.37	无	发展
⑹	164~168	17.5	32.9	13.3	43.6	23.3	0.75	0.76	1.33	无	贯通

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表 12 路基坡脚深层水平位移分布特征值

Table 12 Characteristic values of deep horizontal displacement distribution of subgrade slope foot

模拟加荷过程	匝道基底宽/m	最大位移点深/m	地基软土侧凸面积/m²			软土侧凸衍生沉降均值/mm
模拟加荷过程	匝道基底宽/m	最大位移点深/m	陀螺桩A_a	砂垫层A_b	A_a/A_b	陀螺桩D_a	砂垫层D_b	D_a/D_b
0~145 d	30	2.9	0.105	0.169	0.62	3.5	5.6	0.62
145~260 d	30	2.9	0.398	0.628	0.63	13.3	20.9	0.63

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