掺砂率与干密度对膨润土收缩特性影响

马鸿发; 刘清秉; 李靖

doi:10.19509/j.cnki.dzkq.tb20220099

掺砂率与干密度对膨润土收缩特性影响

doi: 10.19509/j.cnki.dzkq.tb20220099

中国地质大学(武汉)湖北巴东地质灾害国家野外科学观测研究站, 武汉 430074

基金项目:

国家自然科学基金项目 41972298

详细信息

作者简介:
马鸿发(1998—), 男, 现正攻读地质工程专业硕士学位, 主要从事膨润土工程性质方面的研究工作。E-mail: wuther12@qq.com

通讯作者:
刘清秉(1984—), 男, 副研究员, 主要从事特殊土工程性质方面的研究工作。E-mail: liuqingbing_1357@163.com

中图分类号: TU443
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- 文章访问数: 406
- PDF下载量: 39
- 被引次数: 0
出版历程
- 收稿日期: 2022-03-09
- 录用日期: 2022-12-15
- 修回日期: 2022-12-13

Effect of shrinkage characteristics of bentonite with different sand mixing rates and dry densities

Hubei Badong National Observation and Research Station of Geohazards, China University of Geosciences(Wuhan), Wuhan 430074, China

摘要

摘要:
膨润土具有明显胀缩性, 收缩引起膨润土的强度变化并伴随着裂隙的产生, 对工程结构安全有非常重要的影响, 研究膨润土的收缩性对工程安全具有重要意义。通过对膨润土开展恒温干燥收缩试验, 结合数字图像技术, 从干密度和掺砂率2个方面研究其对土体干燥收缩过程中水分蒸发、各向收缩应变和裂隙的影响。土体的干燥收缩过程可以分为减速阶段和残余阶段, 高干密度和高掺砂率土样在干燥收缩过程中失水更少、各向收缩应变更小、裂隙更少。通过扫描电镜试验观察得到高干密度和高掺砂率的土体在微观结构上更加均匀、密实, 孔隙明显减少。针对土样收缩特征模型的选取发现T&D模型数据拟合效果较好。试验表明提高掺砂率和干密度是减小膨润土收缩性的有效手段。
- 膨润土 /
- 掺砂率 /
- 干密度 /
- 干燥收缩 /
- 裂隙
Abstract: Objective
Bentonite is a special soil with obvious expansion and shrinkage, and its strength change caused by shrinkage, accompanied by the formation of fissure has significant impact on the safety of engineering structures.Thereby, investigation on the shrinkage of bentonite is of great importance to engineering safety.
Methods
By carrying out the drying shrinkage test under constant temperature, combined with digital image technology, the effects of dry density and sand mixing rate on water evaporation, anisotropic strain and fissure during the drying shrinkage process of soil were studied.
Results
The results showed that the drying shrinkage process of the soil can be divided into deceleration stage and residual stages. During shrinkage process, the higher the dry density and sand content ratio in soil sample, the less the water loss, the smaller the strain in each direction and the fewer the fissure created. The soil microstructure observed by scanning electron microscopy showed that the higher the dry density and sand content ratio, the more uniform and dense the soil microstructure, and the less the pores in soil. According to the selection of the soil sample shrinkage characteristic model, the T&D model has a better data fitting effect.
Conclusion
Experimental results evidence that increasing the sand addition rate and dry density is an effective means to reduce the shrinkage of bentonite.
- bentonite /
- sand mixing rate /
- dry density /
- dry shrinkage /
- fissure
注释:

(所有作者声明不存在利益冲突)

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图 1 试验装置示意图

Figure 1. Schematic diagram of the test device

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图 2 不同掺砂率土样含水率曲线(a)和蒸发速率曲线(b)

1.5-T.初始干密度为1.5 g/cm³，未掺砂土样；1.5-10T.初始干密度为1.5 g/cm³，掺砂率为10%土样；1.5-20T.初始干密度为1.5 g/cm³，掺砂率为20%土样；1.5-30T.初始干密度为1.5 g/cm³，掺砂率为30%土样；1.5-50T.初始干密度为1.5 g/cm³，掺砂率为50%土样，下同

Figure 2. Moisture content curve (a) and evaporation rate curve (b) for soil samples with different sand content ratios

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图 3 不同初始干密度土样含水率曲线(a)和蒸发速率曲线(b)

Figure 3. Moisture content curve (a) and evaporation rate curve (b) for soil samples with different dry densities

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图 4 不同掺砂率土样的轴向收缩应变曲线(a)和径向收缩应变曲线(b)

Figure 4. Axial strain curves (a) and radial strain curves (b) for soil samples with different sand content ratios

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图 5 不同掺砂率土样校正前(a)、后(b)体积收缩应变曲线

Figure 5. Volume strain curves for soil samples with different sand content ratios before (a) and after (b) calibration

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图 6 不同掺砂率土样收缩应变特征参数

Figure 6. Shrinkage characteristic parameters for soil samples with different sand content ratios

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图 7 不同初始干密度下土样体积收缩应变参数

Figure 7. Volume shrinkage strain parameters for soil samples with different dry densities

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图 8 土样最终裂隙发育状态

a₁, a₂, a₃, a₄.掺砂率0，干密度分别为1.2, 1.3, 1.4, 1.5 g/cm³；b₁, b₂, b₃, b₄.掺砂率10%，干密度分别为1.2, 1.3, 1.4, 1.5 g/cm³；c₁, c₂, c₃, c₄.掺砂率20%，干密度分别为1.2, 1.3, 1.4, 1.5 g/cm³；d₁, d₂, d₃, d₄.掺砂率30%，干密度分别为1.2, 1.3, 1.4, 1.5 g/cm³

Figure 8. Final fissure development status of soil samples

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图 9 不同掺砂率土样表面裂隙率曲线

Figure 9. Surface fissure rate curves for soil samples with different sand content ratios

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图 10 不同初始干密度土样裂隙参数图

Figure 10. Fissure parameters for soil samples with different dry densities

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图 11 初始干密度1.5 g/cm³试样模型拟合曲线

Figure 11. Fitting curves of model for soil sample with dry density of 1.5 g/cm³

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图 12 不同掺砂率微观结构图片

Figure 12. Microstructure pictures for soil sample with different sand content rates

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图 13 不同初始干密度微观结构图片

Figure 13. Microstructure pictures for soil sample with different dry densities

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表 1 膨润土主要化学成分

Table 1. Main chemical components of bentonite

成分	SiO₂	Al₂O₃	Fe₂O₃	MgO	CaO	Na₂O	K₂O	MnO	TiO₂	P₂O₅
w_B/%	61.52	16.62	4.73	5.45	2.73	0.13	0.11	0.03	0.30	0.03

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表 2 膨润土基本物理性质

Table 2. Basic physical properties of bentonite

密度/(g·cm^-3)	液限/%	塑限/%	比表面积/(m²·g^-1)	自由膨胀率/%	线缩率/%	缩限/%	体缩率/%
2.75	155.08	49.54	468.2	155.0	2.22	24.0	27.0

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表 3 干密度1.5 g/cm³模型拟合参数

Table 3. Fitting parameters for soil sample with dry density of 1.5 g/cm³

掺砂率/%	k₀	k₁	k₂	k₃	相关系数R²
0	0.710 95	-0.766 96	2.128 19	-0.976 89	0.997 57
10	0.615 34	-0.471 21	1.712 42	-0.771 90	0.999 30
20	0.658 48	-0.889 31	2.486 71	-1.349 52	0.999 45
30	0.735 41	-1.512 43	3.772 39	-1.949 72	0.999 41
50	0.564 69	-0.798 85	2.221 90	-0.947 26	0.998 14
注：k₀, k₁, k₂, k₃均为模型参数

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