沿海组合地层人工冻结过程中的水分迁移及变形特性

doi:10.16183/j.cnki.jsjtu.2021.057

摘要/Abstract

摘要：

在沿海上软黏下粉砂组合地层中进行人工地层冻结法施工时,粉砂土和软黏土在冻结过程中表现出的水分迁移和变形特性上的差异性不可忽略,是目前较多冻结法工程事故的根源.为了探明两者之间的差异性,通过自制单向冻结仪对原状上海第②₃层灰色粉砂土及重塑上海第④层淤泥质软黏土分别进行冷端温度为 -20、-15、-10 ℃的冻结试验,分析两种土在冻结过程中水分迁移及变形特征的差异.结果表明,粉砂土及软黏土的总变形曲线和分层变形曲线可按土性分为 I 类陡变型曲线(粉砂土)和 II 类缓变型曲线(软黏土),软黏土分层变形曲线在某些分层中还表现出较大的波动性.表明冻结过程中, 软黏土内部水分迁移充分发展,而粉砂土内部大部分水分迅速冻结,迁移不显著.两种土性表现出的变形曲线的差异性和冻结前后的水分分布曲线存在一致对应性.该研究成果可为沿海上软黏下粉砂组合地层冻结法实践中应对冻胀等工程问题的相关措施提出针对性建议.

关键词: 人工地层冻结法, 水分迁移, 粉砂土, 软黏土

Abstract:

The difference in the water migration and the deformation characteristics of silty sand and clay in the freezing process cannot be ignored when the artificial ground freezing method is used in coastal complex strata consisting of clay and silty sand, and is also the root cause of current engineering accidents caused by freezing. In order to find out the difference of the water migration and the deformation characteristics between the silty sand and clay, a self-made single side freezing instrument was used to conduct a series of freezing tests of original silty sand of ②₃ layer and the remodeled clay of ④ layer in Shanghai at a freezing temperature of -20 ℃, -15 ℃, and -10 ℃. The results show that the deformation curves can be divided into steep curve I(silty sand) and gradual curve II(clay). The deformation curves of different layers of clay soil sample fluctuated greatly with time. The results indicate that water migration is fully developed inside the clay during the freezing process, while most of the water inside the silty sand freeze quickly and thus water migration is not developed as obvious as that inside the clay. In addition, the deformation curves of the two types of soils is consistent with the distribution changes of water inside the silty sand and clay after freezing. Based on the research results, specific suggestions can be made for the relevant measures to deal with engineering problems such as frost heave in the practice of the freezing method for coastal complex strata consisted of silty sand and clay.

Key words: artificial ground freezing method, water migration, silty sand, clay

中图分类号:

TU111.2

周洁, 任君杰. 沿海组合地层人工冻结过程中的水分迁移及变形特性[J]. 上海交通大学学报, 2022, 56(5): 675-683.

ZHOU Jie, REN Junjie. Water Migration and Deformation Characteristics of Coastal Complex Strata in Artificial Freezing Process[J]. Journal of Shanghai Jiao Tong University, 2022, 56(5): 675-683.

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试验土样与指标	内摩擦角/(°)	黏聚力/kPa	重度/(kN·cm^-3)	含水率/ %	土粒比重
原状采集软黏土	11.5	14.0	16.90	49.86	2.69
试验用重塑软黏土	11.0	12.7	16.55	48.96	2.69
原状采集粉砂土	28.5	1.4	18.60	28.78	2.71
试验用原状粉砂土	28.3	1.4	18.61	28.69	2.71

试验编号	土样类型	冷端温度/℃
1	原状粉砂土	-10
2	原状粉砂土	-15
3	原状粉砂土	-20
4	重塑软黏土	-10
5	重塑软黏土	-15
6	重塑软黏土	-20

土样	冷端温度/℃	a	b	c	R²
粉砂土	-20	3.2185	0.0023	-11.1340	0.9937
粉砂土	-15	2.6785	0.0029	-10.2072	0.9961
粉砂土	-10	2.2085	0.0010	-8.5531	0.9975
软黏土	-20	1.8151	0.0069	-4.6629	0.9735
软黏土	-15	1.7139	0.0043	-4.2650	0.9924
软黏土	-10	1.7851	0.0035	-5.7038	0.9753