膨胀土的长期回弹特性试验研究

于世祥; 孔令明

doi:10.20265/j.cnki.issn.1007-2993.2024-0485

膨胀土的长期回弹特性试验研究

doi: 10.20265/j.cnki.issn.1007-2993.2024-0485

于世祥,
孔令明^,

北京建筑大学土木与交通工程学院，北京　102616

基金项目: 国家自然科学基金（41902284）；北京市自然科学基金（8204057）；北京市教委一般项目（KM201910016015）

详细信息

作者简介:
于世祥，男，1999年生，在读硕士研究生，主要从事岩土与地下工程研究。E-mail：yushixiang99@163.com

通讯作者:
孔令明，男，1988年生，博士，副教授，主要从事土的基本力学特性和本构模型等研究。E-mail：konglingming@bucea.edu.cn

中图分类号: TU411
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出版历程
- 收稿日期: 2024-10-23
- 修回日期: 2024-12-20
- 录用日期: 2025-03-06
- 刊出日期: 2026-02-06

Experimental study on long-term rebound characteristics of expansive soil

YU Shixiang,
KONG Lingming^,

Beijing University of Civil Engineering and Architecture, School of Civil and Transportation Engineering, Beijing 102616, China

摘要

摘要: 为研究膨胀土的长期回弹变形特性，以人工配置的具有不同膨胀潜势的饱和膨胀土为研究对象，开展了不同应力水平下的长期侧限回弹试验。研究发现：（1）卸荷过程中，弱膨胀土表现出良好的线性回弹特征，而强膨胀土表现出高度非线性；（2）卸荷后的长期回弹变形可划分为主回弹变形、次固结变形两部分；当强膨胀土的回弹率小于极限回弹率，变形两阶段均存在；回弹率达到极限回弹率后，主回弹阶段消失，次固结阶段占据整个变形过程；（3）膨胀土自由膨胀率越大，其压缩指数、回弹指数、极限回弹率越大，临界卸荷比越小，极限回弹率与自由膨胀率之间存在明显的线性关系；（4）随自由膨胀率的增大，次固结系数呈指数型增加，次固结阶段开始时间推迟。
- 膨胀土 /
- 自由膨胀率 /
- 次固结 /
- 回弹 /
- 卸荷
Abstract: To investigate the long-term rebound deformation characteristics of expansive soils, a series of confined long-term rebound tests under varying stress levels was conducted on artificially prepared saturated expansive soils with different swelling potentials. The key findings are: (1) During unloading, weak expansive soils demonstrate clear linear rebound characteristics, while strong expansive soils exhibit pronounced nonlinear rebound characteristics. (2) Long-term rebound deformation following unloading consists of two distinct components: primary rebound deformation and secondary consolidation deformation. When the rebound rate of strong expansive soil is less than the ultimate rebound rate, both deformation stages exist. After the rebound rate reaches the ultimate rebound rate, the primary rebound deformation disappears, and the secondary consolidation deformation occupies the entire deformation process. (3) As the free swell ratio of expansive soils increases, so do the compression index, rebound index, and ultimate rebound ratio, while the critical unloading ratio decreases. A strong linear correlation is observed between the ultimate rebound ratio and the free swell ratio. (4) As the free swell ratio increases, the secondary consolidation coefficient grows exponentially, and the onset of the secondary consolidation stage is delayed.
- expansive soil /
- free swell ratio /
- secondary consolidation /
- rebound /
- unloading

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图 1 混合土样的颗粒级配曲线

Figure 1. Particle gradation curve of mixed soil samples

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图 2 侧限变形曲线

Figure 2. Confined deformation curve

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图 3 压缩指数和回弹指数与自由膨胀率的关系

Figure 3. Relationship between compression index, rebound index and free swell rate

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图 4 卸荷过程的e-t曲线

Figure 4. Unloading e-t curve

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图 5 e - t关系曲线三阶段划分示意图

Figure 5. Three-stage division schematic of e-t curve

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图 6 回弹变形量和吸水量随时间的变化曲线（数据来源于文献[15]）

Figure 6. Curves of rebound deformation and water absorption capacity vs. time

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图 7 e - t关系曲线两阶段划分示意图

Figure 7. Two-stage division schematic of e-t curve

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图 8 试样回弹率曲线

Figure 8. Rebound rate curve of the test sample

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图 9 极限回弹率与自由膨胀率的关系

Figure 9. Correlation between ultimate rebound rate and free swell rate

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图 10 次固结系数与自由膨胀率的关系

Figure 10. Correlation between coefficient of secondary consolidation and free swell rate

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图 11 次固结开始时间与自由膨胀率的关系

Figure 11. Correlation between secondary consolidation onset time and free swell rate

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表 1 膨润土主要矿物成分

Table 1. Main mineral components of bentonite

矿物名称	含量/%
蒙脱石	45.8
斜发沸石	22.8
长石	18.6
方解石	4.4
石英	4.1

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表 2 膨润土物理性质指标

Table 2. Physical property indicators of bentonite

指标名称	指标值
膨胀指数/(mL/2g)	25.0
阳离子交换量/(cmol∙kg⁻¹)	62.1
比重	2.71
液限/%	153.4
塑限/%	26.8
塑性指数	126.6

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表 3 混合土样的物理性质指标

Table 3. Physical properties of mixed soil samples

组别	膨润土掺量/%	饱和含水率/%	饱和度 /%	初始孔隙比	塑性指数	${\delta _{{\text{ef}}}}$/%
A	10	27.6	100	0.69	14.8	56
B	20	25.8	99	0.69	18.9	97
C	30	27.0	100	0.69	30.6	101
D	40	27.4	100	0.69	45.0	106
E	50	30.0	100	0.69	67.9	109

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表 4 试样的回弹率

Table 4. Rebound rate of the test sample

组别	回弹率$\lambda $
组别	R=0.5	R=0.75	R=0.875	R=0.94	R=0.97	${\lambda _{\max }}$
A	−0.0002	−0.0012	−0.0010	0.0005	0.0007	0.0007
B	−0.0004	0.0009	0.0108	0.0339	0.0328	0.0343
C	−0.0004	0.0157	0.0382	0.0367	0.0336	0.0393
D	0.0159	0.0415	0.0396	0.0371	0.0341	0.0437
E	0.0208	0.0455	0.0439	0.0409	0.0374	0.0473

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