Investigation on the strength characteristics of frozen lean clay influenced by anisotropy

IF 3.8 2区工程技术 Q1 ENGINEERING, CIVIL

Cold Regions Science and Technology Pub Date : 2025-08-07 DOI:10.1016/j.coldregions.2025.104628

Yu Tang, Jiahui Wang, Ping Yang

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引用次数: 0

Abstract

Artificial ground freezing (AGF) technology is commonly utilized to stabilize adjacent soils and guarantee the safety during subway tunnel construction by inserting freezing pipes into the ground to form a frozen soil mass. Nonetheless, inclined installation of freezing pipes, aside from the conventional horizontal or vertical configurations, frequently arises due to the complex subterranean pipelines and restricted construction areas. The directional dependence of mechanical properties of lean clay under such conditions remains insufficiently investigated. To address this issue, it is essential to systematically analyze the coupled effect of freezing temperature and sampling angle on the mechanical behavior of lean clay, which is commonly encountered in shield tunnel excavation. Consequently, this study proposed an apparatus and its method for preparing anisotropic clay specimens sampled at various angles ranging from 0° to 90° relative to the natural deposition direction. The anisotropic characteristics of the specimens was verified through the 3D X-ray computed tomography (CT) scanning, focusing on porosity. Uniaxial compressive strength (UCS) tests were then conducted on lean clay specimens prepared by slurry-based consolidation method. The impact of anisotropy on mechanical properties was comprehensively investigated by testing specimens at different sampling angles θ (0°、30°、45°、60° and 90°). The UCS results showed consistent strain-hardening behavior across different sampling angles under subfreezing temperatures of −5 °C, −10 °C and − 15 °C. The combined influences of anisotropy and freezing temperature on the strength of frozen lean clay were discussed by regression analysis. UCS exhibited an exponential decrease with increasing sample angle, and a linear rise with decreasing freezing temperature. A mathematical model was established to predict strength and deformation behavior of lean clay, incorporating the coupled effects of anisotropy and freezing conditions. In addition, the correlation between macroscopic strength and mesoscopic porosity was investigated. The augmentation of porosity resulted in a diminution of frozen soil strength. The research provides a reliable foundation for predicting of mechanical properties of lean clay in the AGF-reinforced engineering of subway tunnel and holds practical engineering significance for disease control.

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各向异性影响下冷冻贫黏土强度特性研究

人工冻结技术是地铁隧道施工中常用的通过在地下插入冻结管形成冻结土体来稳定邻近土体，保证施工安全的技术。然而，由于地下管道复杂，施工区域有限，除了常规的水平或垂直配置外，还经常出现倾斜安装冷冻管的情况。在这种条件下，贫粘土力学性能的方向依赖性还没有得到充分的研究。为了解决这一问题，有必要系统地分析冻结温度和取样角度对盾构隧道开挖中常见的贫黏土力学行为的耦合影响。因此，本研究提出了一种制备相对于自然沉积方向0°~ 90°不同角度的各向异性粘土试样的装置和方法。通过三维x射线计算机断层扫描（CT）验证了试样的各向异性特征，重点关注孔隙率。然后对采用浆基固结法制备的贫粘土试件进行了单轴抗压强度试验。通过不同采样角度θ（0°，30°，45°，60°和90°）的试样，全面研究了各向异性对力学性能的影响。UCS结果显示，在- 5°C、- 10°C和- 15°C的亚冷冻温度下，不同取样角度的应变硬化行为一致。通过回归分析，探讨了各向异性和冻结温度对冻结贫黏土强度的综合影响。随试样夹角的增大，单截面积呈指数下降，随冻结温度的降低，单截面积呈线性上升。建立了考虑各向异性和冻结条件耦合影响的贫黏土强度和变形特性预测数学模型。此外，还研究了宏观强度与介观孔隙率之间的关系。孔隙率的增大导致冻土强度的降低。研究结果为地铁隧道agf加筋工程中贫粘土的力学性能预测提供了可靠的依据，对病害防治具有实际的工程意义。

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来源期刊

Cold Regions Science and Technology 工程技术-地球科学综合

CiteScore

7.40

自引率

12.20%

发文量

209

审稿时长

4.9 months

期刊介绍： Cold Regions Science and Technology is an international journal dealing with the science and technical problems of cold environments in both the polar regions and more temperate locations. It includes fundamental aspects of cryospheric sciences which have applications for cold regions problems as well as engineering topics which relate to the cryosphere. Emphasis is given to applied science with broad coverage of the physical and mechanical aspects of ice (including glaciers and sea ice), snow and snow avalanches, ice-water systems, ice-bonded soils and permafrost. Relevant aspects of Earth science, materials science, offshore and river ice engineering are also of primary interest. These include icing of ships and structures as well as trafficability in cold environments. Technological advances for cold regions in research, development, and engineering practice are relevant to the journal. Theoretical papers must include a detailed discussion of the potential application of the theory to address cold regions problems. The journal serves a wide range of specialists, providing a medium for interdisciplinary communication and a convenient source of reference.