Cold Regions Science and Technology最新文献_第2页

Mesoscopic shear evolution characteristics of frozen soil-concrete interface 冻土-混凝土界面的介观剪切演变特征

IF 3.8 2区工程技术 Q1 ENGINEERING, CIVIL

Cold Regions Science and Technology

Pub Date : 2024-10-22 DOI: 10.1016/j.coldregions.2024.104342

Xusheng Wan , Hao Zhou , Fengxi Zhou , Jishuai Zhu , Khan Muhammad Shahab

The mechanical properties of frozen-concrete interfaces affect the stability and durability of engineering structures in cold regions. To investigate these properties, laboratory tests and numerical simulations were conducted to study the mesoscopic evolution of the shear stress-displacement relationship and the shearing process at the interface. The direct shear tests were performed at different environmental temperatures (−2 °C, −5 °C, and −10 °C) and normal stresses (100 kPa, 200 kPa, and 300 kPa) on the frozen soil-concrete interface, and Particle Flow Code (PFC) model of direct shear was developed. The mesoscopic parameters (particle displacement, rotation, force chain, stress, coordination number, porosity, fabric, etc.) of the interface during shearing were simulated using the PFC model. Moreover, the relationship among the interface temperature, cohesion, and friction coefficient was determined based on experimental data, and the accuracy of the PFC model was verified using previous experimental data. The results of the PFC shear model aligned well with those of the laboratory test, and the formation of shear bands was simulated well. The displacement of the soil particles on the upper layer outside the shear zone was uniform, and the direction was the same, whereas the particles inside the shear zone showed significant differences in the dislocation and rotation of the soil particles. The force chain, stress field, coordination number, and porosity were similar in the shear process and showed a concentrated distribution in the opposite direction of the shear motion, which reflected the consistency of the microcosmic response of the particles under the action of macroscopic external forces. The regression equations for the temperature, cohesion, and friction coefficient in this study can be used to simulate the shear behavior of frozen soil-concrete interfaces under different temperatures and normal stresses.

受冻混凝土界面的力学性能影响着寒冷地区工程结构的稳定性和耐久性。为了研究这些特性，我们进行了实验室试验和数值模拟，以研究剪应力-位移关系的中观演变和界面的剪切过程。在不同的环境温度（-2 °C、-5 °C 和 -10 °C）和法向应力（100 kPa、200 kPa 和 300 kPa）下，对冻土-混凝土界面进行了直接剪切试验，并建立了直接剪切的粒子流代码（PFC）模型。利用 PFC 模型模拟了剪切过程中界面的中观参数（颗粒位移、旋转、力链、应力、配位数、孔隙度、结构等）。此外，还根据实验数据确定了界面温度、内聚力和摩擦系数之间的关系，并利用先前的实验数据验证了 PFC 模型的准确性。PFC 剪切模型的结果与实验室试验的结果吻合，很好地模拟了剪切带的形成。剪切带外上层土体颗粒位移均匀，方向一致，而剪切带内土体颗粒位错和旋转差异明显。在剪切过程中，力链、应力场、配位数、孔隙度等均相似，并呈现出与剪切运动方向相反的集中分布，反映了颗粒在宏观外力作用下微观响应的一致性。本研究中的温度、内聚力和摩擦系数回归方程可用于模拟冻土-混凝土界面在不同温度和法向应力下的剪切行为。

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引用次数: 0

New insights into icephobic material assessment: Introducing the human motion–inspired automated apparatus (HMA) 疏冰材料评估的新见解：人体运动启发自动仪器（HMA）介绍

IF 3.8 2区工程技术 Q1 ENGINEERING, CIVIL

Cold Regions Science and Technology

Pub Date : 2024-10-22 DOI: 10.1016/j.coldregions.2024.104351

Jean-Denis Brassard, Sarah Sobhani, Maria-Lucia Loaiza Osorio, Gelareh Momen

The impact of winter on exposed structures and transportation poses significant dangers and costs to various industries, particularly the transportation sector. Icephobic surfaces are currently being developed to reduce winter-related impacts. Creating such surfaces requires considering various factors, including reducing and preventing ice accumulation, significantly decreasing ice adhesion, and/or delaying water solidification. Although established methods such as centrifugal force and push-off tests exist for measuring ice adhesion, the results may not always correlate or offer the needed information for specific applications. To better assess icephobic properties, we have developed a novel device called the human motion–inspired automated apparatus (HMA) that mimics manual de-icing performed by humans in a scraping mode. The primary objective of the HMA is to emulate human removal of ice-covered surfaces, providing a more realistic evaluation of icephobic properties according to the ease of ice removal. This apparatus aims to revolutionize icephobic material assessment by offering improved accuracy, repeatability, and versatility in testing. We developed a unique procedure using low icing conditions, which are challenging to evaluate using conventional methods, and assessed four surfaces: aluminum as a reference, an epoxy-based hydrophilic coating, a hydrophobic silicone elastomer coating, and a hydrophobic epoxy–silicone coating. Our HMA characterizes surfaces according to several crucial parameters, including the normal force required to initiate ice scraping removal, the maximum force achieved, the angle of attack, and the equivalent force, all consistent with validation tests conducted by humans. Among the evaluated surfaces, the silicone coating required the lowest normal force, and the epoxy–silicone coating had the lowest maximum and equivalent forces. Our HMA results align well with validation tests conducted by humans. The HMA enables evaluating various critical icing conditions and promises a broad range of applications in research and development.

冬季对裸露结构和运输的影响给各行各业，尤其是运输业带来了巨大的危险和成本。目前正在开发疏冰表面，以减少与冬季有关的影响。创建此类表面需要考虑各种因素，包括减少和防止冰的积累、显著降低冰的附着力和/或延迟水的凝固。虽然已有离心力和推脱试验等测量冰附着力的成熟方法，但其结果并不总是相关联，也不能提供特定应用所需的信息。为了更好地评估憎冰特性，我们开发了一种名为 "人体运动启发自动装置（HMA）"的新型装置，该装置可模仿刮冰模式下的人工除冰。HMA 的主要目的是模拟人类清除冰雪覆盖表面的过程，根据除冰的难易程度对疏冰特性进行更真实的评估。该仪器旨在通过提高测试的准确性、可重复性和多功能性，彻底改变疏冰材料评估方法。我们利用传统方法难以评估的低结冰条件开发了一种独特的程序，并对四种表面进行了评估：作为参照的铝、环氧基亲水涂层、疏水性硅弹性体涂层和疏水性环氧硅涂层。我们的 HMA 根据几个关键参数对表面进行表征，包括启动刮冰去除所需的法向力、达到的最大力、攻击角度和等效力，所有这些参数都与人类进行的验证测试一致。在所评估的表面中，硅树脂涂层所需的法向力最小，环氧硅树脂涂层的最大力和等效应力最小。我们的 HMA 结果与人类进行的验证测试非常吻合。HMA 可以评估各种关键结冰条件，有望在研发领域得到广泛应用。

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引用次数: 0

Enhancing artificial permafrost table predictions using integrated climate and ground temperature data: A case study from the Qinghai-Xizang highway 利用综合气候和地温数据加强人工冻土层表预测：青藏公路案例研究

IF 3.8 2区工程技术 Q1 ENGINEERING, CIVIL

Cold Regions Science and Technology

Pub Date : 2024-10-18 DOI: 10.1016/j.coldregions.2024.104341

Yu-Zhi Zhang , Shao-Jie Liang , Jian-Bing Chen , Meng Wang , Ming-Tao Jia , Ya-Ting Jiang

The complexities of permafrost changes, driven by climate warming and engineering activities, coupled with challenges in data acquisition, make it crucial and challenging to accurately predict the artificial permafrost table, particularly for subgrades in high-temperature unstable permafrost regions. To address this, this study developed a hybrid machine learning model (RF-LSTM-XGBoost) for permafrost table prediction. By analyzing climate change and ground temperature data from various positions and depths along the subgrade in the Tuotuo River section of the Qinghai-Xizang Highway, the Spearman correlation coefficient method was initially used to determine the important influencing factors. Random Forest (RF), Long Short-Term Memory Neural Network (LSTM), and Extreme Gradient Boosting (XGBoost) models were used to predict the artificial permafrost table, and grid search and cross-validation methods were employed to optimize the hyperparameters of each model. A linear weighted combination method based on the minimum cumulative absolute error was utilized to merge the models, and its performance was compared with the individual RF, LSTM, and XGBoost models. Subsequently, the feature importance of the variables in the machine learning model was analyzed. The results indicated a strong correlation between artificial permafrost table changes and factors such as daily average atmospheric temperature, subgrade surface ground temperature, and subgrade surface ground heat flux during the freezing-thawing cycle. The combined model highlighted daily atmospheric temperature as the most influential predictor, followed by ground heat flux, with the surface ground temperature being less impactful. The combined model demonstrated improved predictive accuracy, with MSE, MAPE, RMSE, MAE, and R² values of 0.003, 0.052, 0.0085, 0.029, and 0.989, respectively, surpassing those of individual models. This model offers a rapid, accurate, and reliable approach for permafrost table prediction, advancing subgrade stability research in challenging permafrost environments.

在气候变暖和工程活动的驱动下，冻土层的变化十分复杂，再加上数据采集方面的挑战，因此准确预测人工冻土层表，尤其是高温不稳定冻土地区的下层冻土层表至关重要且极具挑战性。为此，本研究开发了一种用于冻土层预测的混合机器学习模型（RF-LSTM-XGBoost）。通过分析青藏公路沱沱河段路基沿线不同位置和深度的气候变化和地温数据，初步采用斯皮尔曼相关系数法确定了重要的影响因素。采用随机森林（RF）、长短期记忆神经网络（LSTM）和极梯度提升（XGBoost）模型预测人工冻土层表层，并采用网格搜索法和交叉验证法优化各模型的超参数。利用基于最小累积绝对误差的线性加权组合方法合并模型，并将其性能与 RF、LSTM 和 XGBoost 模型进行比较。随后，分析了机器学习模型中变量特征的重要性。结果表明，在冻融循环期间，人工冻土层表层变化与日平均大气温度、基层表层地温和基层表层地热通量等因素之间存在很强的相关性。综合模型突出显示，日大气温度是影响最大的预测因素，其次是地表热通量，而地表地温的影响较小。组合模型提高了预测精度，其 MSE、MAPE、RMSE、MAE 和 R2 值分别为 0.003、0.052、0.0085、0.029 和 0.989，超过了单个模型。该模型为冻土层表层预测提供了一种快速、准确、可靠的方法，推动了具有挑战性的冻土环境中的路基稳定性研究。

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引用次数: 0

Model test investigation on heat and deformation behaviors of canal slopes with protective layers caused by freeze-thaw action 带有保护层的运河边坡在冻融作用下的受热和变形行为的模型试验研究

IF 3.8 2区工程技术 Q1 ENGINEERING, CIVIL

Cold Regions Science and Technology

Pub Date : 2024-10-05 DOI: 10.1016/j.coldregions.2024.104338

Haiqiang Jiang , Xingchao Liu , Yuwei Chen , Enliang Wang , Qiang Fu , Junlin He , Hua Zhong

Frost damage is one of the main factors affecting the stability of canal slopes in cold regions. To alleviate the damage, laying protective layers during the construction process has become an indispensable measure. In this study, two slope models were constructed using polyester geotextiles (slope I) and composite geomembranes (slope II) as the protective layer. Additionally, the insulation board in the control group were laid on specific section to examine their anti-frost effect. The temperature, frozen depth, and frost deformations of slope models during the freeze-thaw process were recorded and analyzed. Results suggest that the temperature of slope II is relatively lower than that of slope I in the freezing process. The temperature reduction at all monitoring sections of slope II are larger than that of slope I. The slope I exhibits a significant decrease in maximum frozen depth and maximum frost deformation. In particular, the section with the maximum frost deformation is independent of the type of protective layer, which all occurs in the middle of the slopes. The maximum frost deformations of slope models are 33.60 mm and 37.69 mm, respectively after laying the polyester geotextiles and composite geomembranes. Therefore, the polyester geotextiles have more advantages in reducing frost deformation than composite geomembranes. Additionally, if the insulation board and polyester geotextiles are laid together inside the slope, the maximum frost deformation can be further reduced to 9.72 mm. This study will help in the design and construction of canal slopes in cold regions.

冻害是影响寒冷地区运河边坡稳定性的主要因素之一。为了减轻冻害，在施工过程中铺设保护层已成为一项不可或缺的措施。本研究使用聚酯土工织物（边坡 I）和复合土工膜（边坡 II）作为保护层，建造了两个边坡模型。此外，还在特定地段铺设了对照组的保温板，以检验其防冻效果。记录并分析了冻融过程中边坡模型的温度、冻结深度和霜冻变形。结果表明，在冻结过程中，斜坡 II 的温度相对低于斜坡 I。边坡 I 的最大冻结深度和最大冻胀变形均有显著下降。特别是，最大冻胀变形段与保护层类型无关，均出现在斜坡中部。在铺设聚酯土工织物和复合土工膜后，边坡模型的最大冻胀变形分别为 33.60 毫米和 37.69 毫米。因此，聚酯土工织物在减少冻害变形方面比复合土工膜更有优势。此外，如果将保温板和聚酯土工织物一起铺设在斜坡内，最大冻胀变形可进一步减小到 9.72 毫米。这项研究将有助于寒冷地区运河边坡的设计和施工。

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引用次数: 0

Cutting speed and behaviors of ice using Yb-doped fiber laser 使用掺镱光纤激光器切割冰的速度和行为

IF 3.8 2区工程技术 Q1 ENGINEERING, CIVIL

Cold Regions Science and Technology

Pub Date : 2024-10-05 DOI: 10.1016/j.coldregions.2024.104335

Merlin L. Mah , Andrei V. Kurbatov , Joseph J. Talghader

The use of a laser to cut or drill ice has been proposed and demonstrated multiple times in previous decades as a novel, but never adopted, machining tool in glaciology and paleoclimate studies. However, with the rapid development of high power fiber-laser technology over the past few decades, it is timely to perform further studies using this new tool. An investigation is made herein on the cutting of ice using a Yb-doped fiber laser emitting at a wavelength of 1070 nm, the most extensively developed and highest power fiber laser technology, in pulsed and continuous-wave operation. Visible-light observations of clear tap water ice samples, moving at a constant velocity relative to a pulsed laser beam, demonstrate a linear relationship between the duration of a millisecond-range laser pulse and the depth of the meltwater-free cut formed in response. Thermal imaging of the irradiated face shows that peripheral heating trends linearly for pulse lengths greater than 5 ms. A comparison of pulse trains with a constant time-averaged power suggests that shorter pulses are advantageous in slot-cutting efficiency and in minimizing visible alterations in the surrounding ice. These results demonstrate the viability of powerful fiber-compatible lasers as a tool for ice sample retrieval and processing.

在过去的几十年中，使用激光切割或钻孔冰作为一种新颖的加工工具在冰川学和古气候研究中被多次提出和论证，但从未被采用。然而，随着高功率光纤激光技术在过去几十年的快速发展，现在是利用这种新工具开展进一步研究的时候了。本文对使用波长为 1070 纳米的掺镱光纤激光器切割冰层的情况进行了研究，该激光器是目前开发最广泛、功率最大的光纤激光器技术，可进行脉冲和连续波操作。对相对于脉冲激光束匀速运动的透明自来水冰样品进行的可见光观察表明，毫秒级激光脉冲的持续时间与响应形成的无融水切割深度之间存在线性关系。照射面的热成像显示，当脉冲长度大于 5 毫秒时，外围加热呈线性趋势。对具有恒定时间平均功率的脉冲序列进行的比较表明，较短的脉冲在切槽效率和最大限度地减少周围冰层的可见变化方面具有优势。这些结果表明，功能强大的光纤兼容激光器可作为冰样品回收和处理的工具。

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引用次数: 0

Effectiveness evaluation of cooling measures for express highway construction in permafrost regions based on GPR and ERT 基于 GPR 和 ERT 的冻土地区快速公路建设冷却措施效果评估

IF 3.8 2区工程技术 Q1 ENGINEERING, CIVIL

Cold Regions Science and Technology

Pub Date : 2024-10-03 DOI: 10.1016/j.coldregions.2024.104339

Yunhui Huang , Fujun Niu , Peifeng He , Weidong Pan , Kun Yuan , Wenji Su

Global warming and human activities are accelerating the degradation of permafrost on the Qinghai-Tibet Plateau (QTP), leading to significant settlement and cracking issues in the local express highway infrastructures. In response, the Gonghe-Yushu Express Highway (GYE) on the east edge of the QTP incorporated extensive cooling measures during its construction to enhance embankment stability. Despite these efforts, field investigations have disclosed that embankment diseases persist across various sections, including those with implemented cooling measures. This study focuses on a specific test and demonstration section of the GYE, employing a suite of cooling measures to assess their engineering effectiveness. Utilizing a combination of multi-time ground-penetrating radar (GPR) and electrical resistivity tomography (ERT) detection, alongside on-site disease investigations and temperature monitoring, this research comprehensively evaluates the efficacy of different cooling interventions. Findings indicate that although cooling measures generally curb permafrost degradation in areas with ice-rich and ice-saturated soils, they fall short in sections with massive ground ice. Of the six cooling measures examined in the demonstration section, ventilation duct embankments emerge as the most effective, whereas crushed-rock layer embankments rank as the least. The study further reveals that the combined use of XPS insulation boards and two-phase closed thermosyphons inadequately addresses the issue of central heat accumulation in broad-width express highways, reducing uneven settlement issues but aggravating longitudinal cracking. Comparative analysis of on-site surveys and monitoring data suggests that regular application of GPR and ERT techniques can proficiently assess the performance of cooling measures.

全球变暖和人类活动正在加速青藏高原（QTP）冻土层的退化，导致当地高速公路基础设施出现严重的沉降和开裂问题。为此，位于青藏高原东缘的共和至玉树高速公路（GYE）在建设过程中采取了大量降温措施，以增强路堤的稳定性。尽管做出了这些努力，但实地调查显示，不同路段的路堤病害依然存在，包括已采取降温措施的路段。本研究主要针对青羊河的一个特定试验和示范段，采用一系列冷却措施来评估其工程效果。这项研究结合使用了多时间探地雷达 (GPR) 和电阻率断层扫描 (ERT) 探测技术，以及现场疾病调查和温度监测，全面评估了不同冷却干预措施的效果。研究结果表明，虽然在富冰和冰饱和土壤地区，降温措施一般都能遏制冻土层退化，但在有大量地表冰的地段，降温措施就显得力不从心了。在示范区研究的六种降温措施中，通风管道堤坝最为有效，而碎石层堤坝的降温效果最差。研究进一步揭示，结合使用聚苯乙烯保温板和两相封闭式温水箱不足以解决宽幅快速公路的中心热量积聚问题，虽然减少了不均匀沉降问题，但却加剧了纵向开裂。对现场调查和监测数据的比较分析表明，定期应用 GPR 和 ERT 技术可有效评估冷却措施的性能。

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引用次数: 0

Applicability of two-phase modeling with compression experiments for snow compaction dynamics 两相模型与压缩实验在雪地压实动力学中的适用性

IF 3.8 2区工程技术 Q1 ENGINEERING, CIVIL

Cold Regions Science and Technology

Pub Date : 2024-10-02 DOI: 10.1016/j.coldregions.2024.104336

B. Ilyse Horlings , Zoe Courville , Andrii Murdza , Kaitlin M. Keegan

Compaction is a rheological process which, in many fields, has been modeled using a 1-D two-phase continuum framework. However, only recently has it been posed as a promising method for modeling the densification of snow into glacial ice, where the conventional model is empirical or semi-empirical. Here, we explore the applicability of a standard one-dimensional two-phase continuum framework for modeling snow compaction through theoretical and laboratory methods by analyzing and simplifying theory, and then experimentally constraining the model coefficient. We find in our theory analysis that the limit of slow compaction is reached such that air evacuation during the compaction process does not impede the deformation of ice grains. Model-data comparisons are performed using data from a series of uniaxial compression experiments of snow samples under a range of compaction rates (1 × 10⁻⁶ to 3 × 10⁻⁵ m s⁻¹) and densities (250 to 450 kg m⁻³) at −10° and –20 °C, which show good measures of fit (

r^{2}

>0.996). By defining a linear effective pressure function, we then constrain the model parameter by tuning against the data. While our model follows proper simplification of theory, the temperature and microstructural dependence are determined exclusively by the model parameter in a rheological formulation with the strain rate, and much scatter still exists. Within the selected range of compaction rates and densities, our results indicate that a 1-D two-phase model with a continuum framework alone does not likely capture important processes involved in the compaction process.

压实是一种流变过程，在许多领域都使用一维两相连续框架进行建模。然而，直到最近，它才被认为是一种很有前途的方法，可用于模拟积雪变成冰川冰的致密化过程，而传统的模型都是经验或半经验模型。在这里，我们通过理论分析和简化理论，然后通过实验对模型系数进行约束，探索了标准一维两相连续体框架在模拟积雪压实方面的适用性。我们在理论分析中发现，达到缓慢压实的极限时，压实过程中的空气排空不会阻碍冰粒的变形。在-10°和-20°C条件下，我们使用一系列雪样单轴压缩实验的数据进行了模型与数据的比较，结果显示拟合度良好（r2>0.996）。通过定义线性有效压力函数，我们可以根据数据调整模型参数。虽然我们的模型遵循了适当的简化理论，但温度和微观结构依赖性完全由流变公式中的模型参数和应变率决定，因此仍然存在很大的分散性。在选定的压实速率和密度范围内，我们的结果表明，仅采用连续体框架的一维两相模型不可能捕捉到压实过程中的重要过程。

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引用次数: 0

A systematic investigation of the freezing process of silty clay through unidirectional stepwise freezing method combined with digital imaging processing technology 结合数字图像处理技术的单向分步冻结法对淤泥质粘土冻结过程的系统研究

IF 3.8 2区工程技术 Q1 ENGINEERING, CIVIL

Cold Regions Science and Technology

Pub Date : 2024-10-02 DOI: 10.1016/j.coldregions.2024.104340

Yongtao Wang , Xiangtian Xu , Zuoyu Guo , Dayan Wang , Yuhang Liu , Jiwei Wang

Soil freezing represents a complex thermo-hydro-mechanical coupling process that encompasses a range of physical and mechanical phenomena, such as heat transfer, moisture migration, cryostructure development, ice lens segregation, frost heave, and consolidation, all of which interact and influence one another throughout the freezing process. This study conducted a unidirectional stepwise freezing test, comprising three distinct freezing stages, to investigate the freezing behavior of Qinghai-Tibet silty clay using digital imaging processing technology (DIPT), which includes an image acquisition system and a digital image processing system. The results demonstrate that the stepwise freezing test provides a more comprehensive insight into the physical and mechanical processes occurring during unidirectional soil freezing. At various stages of freezing, the temperature distribution within the sample achieves a linear stabilization, with the frozen zone exhibiting a slightly larger extent compared to the unfrozen zone. The longitudinal section of the sample developed layered cryogenic cracks, whereas the horizontal section revealed interconnected cryogenic polygonal cracks of varying sizes, which facilitated moisture migration and ice segregation. Furthermore, ice lenses can segregate within a broad temperature range below the soil freezing point in the frozen zone, resulting in frost heave within the frozen zone and consolidation of the unfrozen zone. This study proposes an experimental method to clarify the complex phenomenon and mechanisms of frost heave during soil freezing.

土壤冻结是一个复杂的热-水-机械耦合过程，包括一系列物理和机械现象，如热传导、水分迁移、冰冻结构发展、冰晶体离析、冻胀和固结等，所有这些现象在整个冻结过程中相互作用、相互影响。本研究利用数字图像处理技术（DIPT）（包括图像采集系统和数字图像处理系统）对青藏淤泥质粘土的冻结行为进行了单向分步冻结试验，包括三个不同的冻结阶段。结果表明，分步冻结试验能更全面地了解土壤单向冻结过程中发生的物理和力学过程。在冻结的不同阶段，样品内部的温度分布实现了线性稳定，与未冻结区相比，冻结区的范围略大。样本的纵向断面出现了分层的低温裂缝，而横向断面则出现了相互连接的大小不等的多边形低温裂缝，这有利于水分迁移和冰析出。此外，冰透镜体可在冻结区低于土壤冰点的较大温度范围内发生离析，导致冻结区内的冻胀和未冻结区的固结。本研究提出了一种实验方法，以阐明土壤冻结期间冻胀的复杂现象和机理。

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引用次数: 0

Monitoring evolutionary damage of bended concrete beams subjected to freeze-thaw cycling through piezoelectric-enabled wave propagation method 通过压电波传播方法监测受冻融循环影响的弯曲混凝土梁的进化损伤

IF 3.8 2区工程技术 Q1 ENGINEERING, CIVIL

Cold Regions Science and Technology

Pub Date : 2024-09-30 DOI: 10.1016/j.coldregions.2024.104337

Qixiang Yan , Yunhui Qiu , Chuan Zhang , Zhengyu Xiong , Xiaolong Liao , Caihou Xu

Tunnels in cold regions are often subjected to freeze-thaw cycling, which poses a great challenge to a large number of tunnels in operation or to be built in these regions. Therefore, structural health monitoring (SHM) for lining concrete in cold regions is essential to ensure the safety and long-term operation of tunnels. In this study, the wave propagation method (WPM) is applied for the first time to monitor the cyclic freeze-thaw damage of lining concrete. First of all, the failure behaviors of concrete beams subjected to the coupling effect of flexural loading and freeze-thaw cycling are investigated. Particularly, the authors propose a refined numerical model to simulate the freeze-thaw cycling damage process of concrete beams considering the ice-water phase transition and concrete elastoplastic damage. Based on the numerical results, the internal damage expansion and flexural strength attenuation of concrete beams are revealed. Furthermore, the dynamic attenuation characteristics of stress waves are analyzed by using the wavelet packet decomposition and continuous wavelet transform to reveal. In addition, the WPM-based energy index is proposed to characterize the freeze-thaw damage degree of the lining concrete. A strong correlation is found between the stress wave signal and freeze-thaw damage, with a favorable correlation coefficient of 0.932, suggesting the excellent performance of the WPM in assessing the freeze-thaw damage of lining concrete. This research sufficiently manifests the applicability of the WPM method to monitoring the freeze-thaw damage within cold regional tunnel linings.

寒冷地区的隧道经常受到冻融循环的影响，这给这些地区大量正在运营或即将建设的隧道带来了巨大挑战。因此，寒冷地区衬砌混凝土的结构健康监测（SHM）对于确保隧道的安全和长期运营至关重要。本研究首次采用波传播法（WPM）监测衬砌混凝土的循环冻融破坏。首先，研究了混凝土梁在挠曲荷载和冻融循环耦合作用下的破坏行为。特别是，考虑到冰水相变和混凝土弹塑性破坏，作者提出了一个精细的数值模型来模拟混凝土梁的冻融循环破坏过程。基于数值结果，揭示了混凝土梁的内部损伤扩展和抗弯强度衰减。此外，利用小波包分解和连续小波变换分析了应力波的动态衰减特性。此外，还提出了基于 WPM 的能量指数来表征衬砌混凝土的冻融破坏程度。研究发现，应力波信号与冻融破坏之间具有很强的相关性，相关系数高达 0.932，表明小波包分解技术在评估衬砌混凝土冻融破坏方面具有优异的性能。这项研究充分体现了 WPM 方法在监测寒冷地区隧道衬砌冻融破坏方面的适用性。

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引用次数: 0

Experimental investigations of the shear strength and deformation behavior of a frozen unsaturated silt 冰冻非饱和淤泥的剪切强度和变形行为实验研究

IF 3.8 2区工程技术 Q1 ENGINEERING, CIVIL

Cold Regions Science and Technology

Pub Date : 2024-09-24 DOI: 10.1016/j.coldregions.2024.104332

Hao Wang , Xu Li , Wenhao Huang , Sai K. Vanapalli

There are limited studies in literature with respect to the deformation and shear strength behavior of frozen unsaturated soils that consider sensitive changes in temperatures below 0 °C. For this reason, the focus of the present study is directed towards investigating the shear strength and deformation behavior of a frozen unsaturated silt. As a part of the study, one-dimensional freezing tests were performed on compacted silt samples with various initial water contents and dry densities. The pulsed nuclear magnetic resonance (P-NMR) method was used to obtain distribution of unfrozen water content of silt samples; this information was used to explain the deformation behavior during freezing. The volume change behavior in unsaturated soils due to freezing can be associated to three primary factors: expansion caused by the ice-water phase transition and shrinkage induced by ice-cementation and dehydration. A critical water saturation was also observed at which the frost heave is minimum, or no volume change occurs. In addition, conventional direct shear tests were performed on compacted unsaturated silt samples both in frozen and unfrozen conditions to determine and quantify the shear strength contribution arising from the different cohesion components. The investigations in this study provide valuable information that can be used in rational explanation of the strength and deformation behavior of unsaturated frozen soils.

关于冻结非饱和土壤的变形和剪切强度行为，考虑到 0 °C 以下温度的敏感变化的文献研究非常有限。因此，本研究的重点是调查冻结非饱和淤泥的剪切强度和变形行为。作为研究的一部分，对具有不同初始含水量和干密度的压实淤泥样本进行了一维冻结试验。利用脉冲核磁共振（P-NMR）方法获得了淤泥样品未冻结含水量的分布情况；这一信息被用来解释冻结过程中的变形行为。非饱和土壤在冻结过程中的体积变化行为主要与三个因素有关：冰-水相变引起的膨胀以及冰凝结和脱水引起的收缩。此外，还观察到一个临界水饱和度，在这个临界点上，冻胀最小或不发生体积变化。此外，还在冰冻和非冰冻条件下对压实的非饱和淤泥样本进行了传统的直接剪切试验，以确定和量化不同内聚力成分对剪切强度的贡献。这项研究提供了宝贵的信息，可用于合理解释非饱和冻土的强度和变形行为。

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引用次数: 0