冻融围压作用下冻融软土孔压发展及微观结构试验研究

许超; 王龙泉; 陈峰; 肖丹丹; 黄自凯; 唐小东; 张俊寒

doi:10.20265/j.cnki.issn.1007-2993.2024-0334

冻融围压作用下冻融软土孔压发展及微观结构试验研究

doi: 10.20265/j.cnki.issn.1007-2993.2024-0334

中国联合工程有限公司，浙江杭州　310000

基金项目: 浙江省自然科学基金（ZJXL-JTT-202222）

详细信息

作者简介:
许　超，男，1987年生，大学专科，高级工程师，主要研究方向：土木工程。E-mail：xuc3@chinacuc.com

通讯作者:
陈　峰，男，1995年生，硕士研究生，工程师，主要研究方向：岩土工程。E-mail：chenfeng@chinacuc.com

中图分类号: TU411
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出版历程
- 收稿日期: 2024-07-20
- 修回日期: 2025-02-27
- 录用日期: 2025-03-10
- 网络出版日期: 2025-12-08
- 刊出日期: 2025-12-08

Pore pressure development of freeze-thaw soft soil under cyclic loading

China United Engineering Co., Ltd., Hangzhou 310000, Zhejiang, China

摘要

摘要: 人工冻结法以其成本低、安全性高而广泛应用于地铁隧道工程中。软土经冻融作用后力学性质将发生改变，通过动三轴试验，对冻融软土在不同冻结温度和冻融围压（P_F-T）下的轴向累积应变、刚度以及孔压发展情况进行研究，并在二次对数模型的基础上建立循环荷载作用下冻融软土的动孔压预测模型。基于核磁共振试验，研究P_F-T对冻融土样孔隙分布的影响规律。研究结果表明：土样内部结构在P_F-T的作用下达到平衡，且P_F-T对土样变形的约束作用随P_F-T增大而逐渐减小；冻结温度越低，土体受冻胀效应越明显；随着冻融围压的增加，土样的刚度软化程度逐渐减弱；土样在冻融过程中，P_F-T的增大促使土体内部损伤骨架挤密作用更明显。经初次冻融后土体的力学性能衰减程度最大，2次、3次冻融后将加重已有的结构损伤区，同时带来新的结构损伤。冻融过程中，施加的P_F-T越大，未冻水增加，冻胀作用减小，融土骨架结构越紧实。研究成果可为预测循环荷载作用下冻融软土的孔压发展提供理论依据。
- 人工冻结法 /
- 孔压模型 /
- 冻结温度 /
- 冻融围压 /
- 孔径分布
Abstract: Artificial freezing method is widely used in subway tunnel engineering because of its low cost and high safety. The mechanical properties of soft soil will change after freezing and thawing. The development of axial cumulative strain, stiffness and pore water pressure of frozen and thawed soft soil under different freezing temperatures and freezing and thawing confining pressure P_F-T was studied through dynamic triaxial tests, and the dynamic pore water pressure prediction model of frozen and thawed soft soil under cyclic loading was established on the basis of quadratic logarithmic model. Based on the nuclear magnetic resonance test, the influence tf P_F-T on the pore distribution of frozen-thawed soil samples was studied. The research results show that: the internal structure of the soil sample was balanced under the action of P_F-T, and the restraining effect of P_F-T on the deformation of the soil sample gradually decreases with the increase of P_F-T; the lower the freezing temperature, the more obvious the frost heave effect of soil; with the increase of freezing and thawing confining pressure, the stiffness softening degree of soil samples gradually weakens; during the freezing and thawing process of soil samples, the increase of P_F-T promotes the compaction of damaged skeleton in soil. After the first freeze-thaw, the mechanical properties of soil have the greatest attenuation, and after the second and third freeze-thaw, the existing structural damage area will be aggravated and new structural damage will be brought. In the process of freezing and thawing, the larger P_F-T was applied, the more unfrozen water is, the less frost heaving is, and the more compact the skeleton structure is. The research results can provide theoretical basis for predicting the development of pore pressure of frozen-thawed soft soil under cyclic loading.
- artificial ground freezing /
- pore pressure model /
- freezing temperature /
- freez-thaw confining pressure /
- pore distribution

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图 1 试验土样

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图 2 三轴试验系统

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图 3 核磁共振扫描仪

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图 4 累积应变曲线

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图 5 刚度软化曲线

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图 6 冻融围压P_F-T对孔压发展影响

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图 7 冻结温度T对孔压发展影响

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图 8 冻融循环次数F_t对孔压发展影响

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图 9 冻融软土孔压模型拟合情况

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图 10 不同冻融围压下孔隙分布变化

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表 1 试验方案

试样编号	T/℃	q_s/kPa	P_F-T/kPa	P/kPa	f/Hz	F_t	N
S-1	0	30	0	200	1	0	20000
S-2	−10	30	100	200	1	1~3	20000
S-3	−20	30	100	200	1	1~3	20000
S-4	−30	30	100	200	1	1~3	20000
S-5	−10	30	200	200	1	1~3	20000
S-6	−20	30	200	200	1	1~3	20000
S-7	−30	30	200	200	1	1~3	20000
S-8	−10	30	300	200	1	1~3	20000
S-9	−20	30	300	200	1	1~3	20000
S-10	−30	30	300	200	1	1~3	20000
S-11	−10	30	400	200	1	1~3	20000
S-12	−20	30	400	200	1	1~3	20000
S-13	−30	30	400	200	1	1~3	20000

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表 2 拟合参数

T/℃	P_F-T/kPa	A	B	C	拟合度
−10	100	−0.0004	0.0173	0.4027	0.997
	200	−0.0012	0.0283	−0.1711	0.986
	300	−0.0014	0.0282	−1.999	0.980
	400	−0.0011	0.0233	−0.0832	0.973
−20	100	−0.0012	0.0270	0.7515	0.992
	200	−0.0015	0.0292	0.2936	0.991
	300	−0.0007	0.0228	−0.0709	0.985
	400	0.0004	0.0171	0.0733	0.997
−30	100	−0.0013	0.0287	0.7122	0.995
	200	−0.0021	0.0443	−0.4566	0.990
	300	−0.0015	0.0293	0.1407	0.990
	400	−0.0007	0.0283	−0.2437	0.975

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