膨胀土完全软化强度指标试验研究

张坤勇; 徐娜; 陈恕; ENAMULLAHBaba Kalan; 谢宇飞

doi:10.11779/CJGE202011003

膨胀土完全软化强度指标试验研究 English Version

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.
河海大学岩土工程科学研究所,江苏　南京　210024
3.
深圳市水务局,广东　深圳　518000
4.
河南城建学院市政与环境工程学院,河南　平顶山　467036

基金项目:

国家自然科学基金项目 51578214

详细信息

作者简介:
张坤勇(1975—),男,教授,硕士生导师,主要从事土的基本特性,尤其是复杂应力状态下土体本构关系、边坡稳定分析等方面的教学和科研工作。E-mail：ky_zhang@hhu.edu.cn

中图分类号: TU443
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出版历程
- 收稿日期: 2019-09-02
- 网络出版日期: 2022-12-05
- 刊出日期: 2020-10-31

Experimental study on fully softened shear strength of expansive soil

1.
Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering, Hohai University, Nanjing 210024, China
2.
Geotechnical Engineering Institute, Hohai University, Nanjing 210024, China
3.
Water Resources Bureau of Shenzhen Municipality, Shenzhen 518000, China
4.
School of Municipal and Environmental Engineering, Henan University of Urban Construction, Pingdingshan 467036, China

摘要

摘要: 以引江济淮试验段工程项目为依托,开展膨胀土完全软化强度试验,分析了膨胀土完全软化强度指标在不同含水率、剪切速率下的变化规律,并在此基础上与膨胀土干湿循环强度指标展开对比分析。完全软化状态下,膨胀土黏聚力接近0,完全软化强度主要由内摩擦角决定；内摩擦角受含水率影响不大且几乎不受剪切速率影响；黏聚力普遍较小,符合完全软化状态黏聚力接近0的定义。分别采用干湿循环后强度指标和完全软化强度指标,对简单膨胀土边坡开展了干湿循环后浅层稳定性分析。结果表明,和干湿循环试验相比,完全软化试验工作量小,试验周期短,能反映膨胀土边坡浅层滑塌的破坏机理,可用以对膨胀土边坡受干湿循环作用后的浅层稳定性分析。
- 膨胀土 /
- 完全软化强度 /
- 干湿循环 /
- 浅层滑动
Abstract: The fully softened strength tests are carried out on the expansive soil samples from the Yangtze-Huaihe River Water Transfer Project. The fully softened strength indexes under different moisture contents and shear rates are discussed and analyzed. On this basis, they are compared with the shear strength indexes from the wetting-drying cycle direct shear tests on expansive soil. The results show that in the fully softened state, the cohesive force of expansive soil is close to zero, and the fully softened strength is mainly determined by the inernal friction angle. The inernal friction angle is little affected by the moisture content and shear rate. The strength indexes obtained from wetting-dring cycle tests and fully softened tests are applied to the safety analysis of simple expansive soil slope respectively. Compared with the wetting-drying cycle direct shear tests, the fully softened strenght tests need less lab work and shorter test peroid. The fully softened strength indexes can also reflect the failure mechanism of the shallow failure of expansive soil slopes after wetting-drying cycles in practice. It is recommended to apply the fully softened strength indexes in the analysis of the shallow stability of expansive soil slopes after wetting-drying cycles.
- expansive soil /
- fully softened strength /
- wetting-drying cycle /
- shallow failure

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图 1 峰值强度、残余强度及完全软化强度比较

Figure 1. Comparison among peak strength, residual strength and fully softened strength

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图 2 引江济淮试验段K41+600边坡膨胀土

Figure 2. Expansive soil at excavated slope in section K41+600

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图 3 重塑土小饼样

Figure 3. Pie-shaped remolded expansive soil sample

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图 4 完全软化样

Figure 4. Fully softened expansive soil sample

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图 5 四联应变控制式直剪仪

Figure 5. Strain-controlled direct shear apparatus

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图 6 抗剪强度与法向应力关系曲线

Figure 6. Relationship between shear strength and normal stress

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图 7 膨胀土完全软化样在各级法向应力下的抗剪强度

Figure 7. Fully softened shear strengths under different normal stress

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图 8 完全软化强度指标随土样含水率变化曲线

Figure 8. Relationship between fully softened strength indexes and moisture content

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图 9 膨胀土完全软化样在不同剪切速率下的剪切位移-剪应力的关系曲线

Figure 9. Relationship between shear stress and shear displacement under different shear rates

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图 10 不同强度指标计算膨胀土抗剪强度

Figure 10. Calculated values of shear strength with different indexes

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图 11 使用干湿循环强度指标的膨胀土边坡模型

Figure 11. Model of expansive soil slope usimg shear strength indexes from wetting-drying cycle tests

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图 12 使用完全软化强度指标的膨胀土边坡模型

Figure 12. Model of expansive soil slope using shear strength indexes from fully softened tests

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图 13 仅考虑干湿循环过程

Figure 13. Model only considering process of wetting-drying cycles

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图 14 仅考虑完全软化过程

Figure 14. Model only considering fully softened process

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表 1 完全软化试验设计方案

Table 1 Programs of fully softened tests

试验条件编号	试样含水率/%	剪切速率/(mm·min^-1)
^#0	45.0	0.1,0.6,0.8,1.2
^#1	47.5	0.1,0.6,0.8,1.2
^#2	50.0	0.1,0.6,0.8,1.2
^#3	52.5	0.1,0.6,0.8,1.2
^#4	55.0	0.1,0.6,0.8,1.2

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表 2 重塑样抗剪强度试验结果

Table 2 Shear strength results of remolded soil

法向应力/kPa	干湿循环次数
法向应力/kPa	0	1	3	5
12.5	19.2	15.7	12.9	12.7
25.0	23.2	17.9	17.8	17.6
37.5	27.1	22.2	20.7	20.4
50.0	30.6	26.5	24.3	24.3
100	32.3	28.6	27.7	26.9
200	36.3	32.9	29.2	29.0
300	38.9	34.6	33.5	32.9
400	42.3	38.4	35.8	36.1

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表 3 重塑样抗剪强度指标

Table 3 Shear strength indexes of remolded soil

循环次数	高应力段		低应力段
循环次数	c/kPa	ϕ/(°)	c/kPa	ϕ/(°)
0	29.3	1.9	15.5	17.6
1	25.9	1.9	11.4	16.4
3	24.3	1.6	9.6	16.6
5	23.6	1.8	9.3	16.7
注：循环幅度为4%~31%,脱湿温度为40℃。

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表 4 膨胀土完全软化强度指标

Table 4 Fully softened shear strength indexes

土样含水率w/%	剪切速率/(mm·min^-1)
	0.1		0.6		0.8		1.2
	c/kPa	ϕ/(°)	c/kPa	ϕ/(°)	c/kPa	ϕ/(°)	c/kPa	ϕ/(°)
45.0	2.4	25.2	2.1	25.2	1.9	25.2	1.7	24.8
47.5	1.8	25.3	1.5	25.0	1.4	24.9	1.3	24.9
50.0	1.3	24.8	1.1	24.6	1.1	24.8	0.9	24.4
52.5	1.0	24.6	0.8	24.3	0.7	24.1	0.6	23.8
55.0	0.9	24.4	0.8	24.2	0.6	23.9	0.5	23.8

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表 5 边坡土体抗剪强度指标

Table 5 Shear strength indexes of expansive soil slopes

土体埋深/m	初始强度指标		干湿循环强度指标		完全软化强度指标
土体埋深/m	c/kPa	ϕ/(°)	c/kPa	ϕ/(°)	c/kPa	ϕ/(°)
0~2.5	15.5	17.6	9.3	16.7	0.6	23.9
2.5~4.0	29.3	1.9	23.6	1.8	0.6	23.9
4.0~9.0	29.3	1.9	29.3	1.9	29.3	1.9

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