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Controllable hydrophobization of sands with self-healing polymeric microcapsules 利用自修复聚合物微胶囊对泥沙进行可控憎水处理
IF 5.6 1区 工程技术 Q1 ENGINEERING, GEOLOGICAL Pub Date : 2024-05-18 DOI: 10.1007/s11440-024-02294-z
Rui Qi, Ke Chen, Hongjie Lin, Sérgio D. N. Lourenço, Antonios Kanellopoulos

Hydrophobized soils have functional hydrophobic coatings to delay or restrict water infiltration and thus prevent infrastructure failure and long-term degradation. Over time, hydrophobized soils will be subjected to degradation under the action of external stresses, leading to the loss of its functional properties. Microencapsulation approaches, initially developed for self-healing applications emerge as a potential solution to enhance, switch (from hydrophilic) or prolong the longevity of hydrophobized soils. The aim of this study is to produce and investigate the effectiveness of microencapsulation to impart hydrophobicity in granular materials in response to external stimuli. In this research, polydimethylsiloxane (PDMS), with hydrophobic properties, is encapsulated in calcium alginate microcapsules with the ionic gelation method. The effectiveness of the microcapsules to induce hydrophobicity is investigated by mixing sand with microcapsules and quantifying the change of the contact angle and water drop penetration time (measures of hydrophobicity) under an external trigger, i.e., under drying and consecutive wetting–drying cycles. The results show that microcapsules release the hydrophobic cargo (PDMS) during shrinkage. After drying, the PDMS content in sand increased to 0.1–0.8% by mass of sand. The released hydrophobic cargo (PDMS) induced hydrophobicity in sands, reflected by a contact angle increase from 29.7° to at least 87.7°. The amount of polydimethylsiloxane encapsulated is a key parameter controlling the release of hydrophobic cargo. In addition, 4% capsule content in sands is identified as an effective microcapsule content in inducing hydrophobicity.

疏水土具有疏水功能涂层,可延缓或限制水的渗透,从而防止基础设施失效和长期退化。随着时间的推移,疏水土会在外部压力的作用下发生降解,导致其功能特性丧失。最初为自愈应用而开发的微胶囊方法成为一种潜在的解决方案,可增强、转换(从亲水性)或延长疏水土的寿命。本研究的目的是生产和调查微胶囊技术在颗粒材料中对外界刺激赋予疏水性的有效性。在这项研究中,利用离子凝胶法将具有疏水特性的聚二甲基硅氧烷(PDMS)封装在海藻酸钙微胶囊中。通过将沙子与微胶囊混合,并量化接触角和水滴渗透时间(衡量疏水性的指标)在外部触发(即干燥和连续润湿-干燥循环)下的变化,研究了微胶囊诱导疏水性的效果。结果表明,微胶囊在收缩过程中会释放疏水性物质(PDMS)。干燥后,按沙子质量计算,沙子中的 PDMS 含量增加到 0.1-0.8%。释放出的疏水性物质(PDMS)使沙子具有疏水性,接触角从 29.7°增加到至少 87.7°。聚二甲基硅氧烷的封装量是控制疏水货物释放的关键参数。此外,金沙中 4% 的胶囊含量被认为是诱导疏水性的有效微胶囊含量。
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引用次数: 0
Compacted sand–bentonite mixtures for the confinement of waste landfills 用于封闭垃圾填埋场的压实砂膨润土混合物
IF 5.7 1区 工程技术 Q1 Earth and Planetary Sciences Pub Date : 2024-05-17 DOI: 10.1007/s11440-024-02335-7
Robeta Proia, E. Salvatore, P. Croce, G. Modoni
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引用次数: 0
Experimental and analytical study on the reinforcement mechanism of in-pipe deep dynamic compaction in loose sandy soil 松散砂土管内深层动力压实加固机理的试验与分析研究
IF 5.7 1区 工程技术 Q1 Earth and Planetary Sciences Pub Date : 2024-05-15 DOI: 10.1007/s11440-024-02340-w
Ping Li, Xinfei Sun, Jun Yu, Gangqiang Kong, Junjun Chen
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引用次数: 0
Frozen enzyme EICP method for more effective soil improvement 冷冻酶 EICP 法更有效地改良土壤
IF 5.7 1区 工程技术 Q1 Earth and Planetary Sciences Pub Date : 2024-05-14 DOI: 10.1007/s11440-024-02348-2
Samuel Ng, Jian Chu

Enzyme-induced calcite precipitation (EICP) is one of the emerging soil improvement methods. However, when plant-based enzyme is used, the urease enzyme harvested from plants cannot be stored long. This affects large-scale applications of this method. This paper presents a new method that not only enables urease enzyme to be stored for a long duration, but also improves significantly the effectiveness and efficiency of EICP for soil improvement. In this method, the storage duration of soybean derived urease enzyme is prolonged by storing it at negative 20 degrees. The experimental results indicated that the frozen-stored urease enzyme had an activity of 326% higher than that of fresh enzyme. The shear strength of a fine sand treated using the frozen-stored enzyme is 238.8% higher than that using a normal EICP method. Thus, the frozen method not only overcomes the enzyme storage problem, but also offers a much-improved EICP method. The reasons for the higher urease activity and improved strength enhancement are also explained in this paper.

酶诱导方解石沉淀法(EICP)是一种新兴的土壤改良方法。然而,在使用植物酶时,从植物中提取的脲酶不能长期储存。这影响了这种方法的大规模应用。本文提出了一种新方法,它不仅能使脲酶长时间储存,还能显著提高 EICP 在土壤改良中的效果和效率。在这种方法中,大豆提取的脲酶通过在负 20 度的环境中储存,延长了脲酶的储存时间。实验结果表明,冷冻储存的脲酶活性比新鲜酶高出 326%。使用冷冻储存酶处理的细砂的剪切强度比使用普通 EICP 方法处理的细砂高 238.8%。因此,冷冻法不仅克服了酶的储存问题,还大大改进了 EICP 方法。本文还解释了脲酶活性提高和强度增强改善的原因。
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引用次数: 0
Progressive yielding/softening of soil–cement columns under embankment loading: a case study 路堤荷载下土灰柱的渐进屈服/软化:案例研究
IF 5.7 1区 工程技术 Q1 Earth and Planetary Sciences Pub Date : 2024-05-13 DOI: 10.1007/s11440-024-02346-4
Jin-chun Chai, Takenori Hino, Yafei Qiao, Wenqi Ding

An embankment with a fill thickness of 7.5 m was built on a soil–cement column-slab system improved about 15.8 m thick soft subsoil. The embankment was stable for about 5 months after construction, and then, its settlement rate increased rapidly. To avoid the failure of the embankment, 1.0 m thick fill was removed and the embankment was stabilized again. The results of field investigation using all-core boring through a cement deep mixing (CDM) column under the central of the embankment and 3D finite element analysis (FEA) indicate that the most likely mechanism for the observed field behavior is progressive yielding/softening of the upper part of the columns. In FEA, the yielding/softening of the upper part of columns was simulated using strength reduction option and the start of the softening was triggered manually at the time of observed rapid increase in the settlement rate. This case history indicates that in field quality control of CDM columns, identifying local weak part(s) by continuous measuring the strength of the column samples retrieved from all-core boring is important. It is suggested that combination of unconfined compression test as well as needle penetration tests for the cores retrieved can be an economic and practical way to do this.

在土-水泥柱-板系统上修建了填土厚度为 7.5 米的堤坝,改良了约 15.8 米厚的软基土。堤坝在建成后约 5 个月内保持稳定,随后沉降速度迅速加快。为了避免路堤坍塌,我们清除了 1.0 米厚的填土,并重新稳固了路堤。通过对堤坝中央下方的水泥深层搅拌(CDM)柱进行全芯钻孔实地调查和三维有限元分析(FEA)的结果表明,实地观察到的行为最可能的机制是柱子上部的逐渐屈服/软化。在有限元分析中,使用强度降低选项模拟了支柱上部的屈服/软化,并在观察到沉降速度快速增加时手动触发软化开始。这一案例表明,在对 CDM 柱进行现场质量控制时,通过连续测量从全岩心钻孔取回的柱样本的强度来识别局部薄弱部分非常重要。建议对取回的岩心结合进行无约束压缩试验和针入度试验,这是一种经济实用的方法。
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引用次数: 0
Morphology characterization of unsaturated soils under drying-wetting cycles: crack opening and closure 干燥-湿润循环条件下非饱和土壤的形态特征:裂缝开合
IF 5.7 1区 工程技术 Q1 Earth and Planetary Sciences Pub Date : 2024-05-12 DOI: 10.1007/s11440-024-02347-3
Zhuang Zhuo, Weiling Cai, Cheng Zhu, Chao-Sheng Tang, Kaniz Roksana

The volumetric and hydrological responses of clayey soils subjected to drying-wetting (D-W) cycles are of paramount importance for the integrity of geoenvironmental infrastructures. The study aimed to investigate the cracking behavior of clayey soils under D-W cycles by using advanced 2D imaging and 3D scanning techniques to capture the initiation and propagation of desiccation cracks within a soil specimen. The temporal variation in the soil water content and the corresponding 2D digital photography and 3D morphology of cracks were simultaneously monitored, and the cracking characteristics were interpreted. It was found that the time-dependent evaporation process was independent of the D-W cycles. Both 2D and 3D characterization showed the cracking hysteresis phenomenon in the unsaturated soil, which indicates the dependency of the crack opening and closure on the degree of saturation. D-W cycles led to the formation of subcracks and the increase in the total crack length, reflecting the soil degradation. Additionally, it was demonstrated that the 3D characterization exhibited the advantage of capturing the volumetric change and the subtle change in the macroporosity of the cracked soil over the 2D visualization. The current study provides a perspective of combining 2D and 3D characterization for interpreting the volumetric change of cracked soils and enhancing the understanding of the hydromechanical responses and the soil-atmosphere interactions.

粘性土在干燥-湿润(D-W)循环下的体积和水文响应对地质环境基础设施的完整性至关重要。本研究旨在利用先进的二维成像和三维扫描技术,捕捉土壤试样中干燥裂缝的产生和扩展过程,从而研究粘性土壤在干湿循环条件下的开裂行为。同时监测了土壤含水量的时间变化以及相应的二维数字摄影和三维裂缝形态,并对裂缝特征进行了解释。研究发现,与时间相关的蒸发过程与 D-W 周期无关。二维和三维表征均显示了非饱和土壤中的裂缝滞后现象,这表明裂缝的开合与饱和度有关。D-W 循环导致子裂缝的形成和总裂缝长度的增加,反映了土壤退化。此外,与二维可视化相比,三维表征在捕捉开裂土壤的体积变化和宏观孔隙度的微妙变化方面具有优势。当前的研究提供了一个结合二维和三维表征的视角,以解释开裂土壤的体积变化,并加深对水力学响应和土壤-大气相互作用的理解。
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引用次数: 0
Correlation of fabric parameters and characteristic features of granular material behaviour in DEM in constitutive modelling 构造模型中 DEM 中织物参数与颗粒材料行为特征的相关性
IF 5.6 1区 工程技术 Q1 ENGINEERING, GEOLOGICAL Pub Date : 2024-05-11 DOI: 10.1007/s11440-024-02333-9
Farid Khayyer, Md Mizanur Rahman, Md Rajibul Karim

The anisotropic microstructure of granular materials has a profound effect on their macroscopic behaviour and can be characterised using a fabric tensor. To include of fabric in the critical state theory (CST), anisotropic critical state theory (ACST) was proposed by modifying the state parameter ((psi )) of CST to a fabric-dependent dilatancy state parameter ((upzeta )). Noteworthy that (uppsi) showed a very strong correlation with characteristic features (e.g. instability, phase transformation and characteristic state) of macroscopic behaviour and, as a result, it has been adopted in many constitutive models. While (upzeta) aided the inclusion of fabric in ACST models, the correlation between (upzeta) and characteristic features has not been evaluated in detail yet, although a large number of works are found on micromechanics and fabric only. In this study, a large number of discrete element method simulations for drained and undrained triaxial were conducted to evaluate the correlation between (upzeta) and characteristic features. To this purpose, the correlation between stress ratio and both classic and dilatancy state parameter ((psi) and (upzeta)) were studied in important characteristic features (e.g. instability, phase transformation and characteristic state). It was found that this correlation was improved using (upzeta) which might be due to the inclusion of fabric in our model. This observation is new and significant for inclusion of fabric evolution in constitutive modelling.

粒状材料的各向异性微观结构对其宏观行为有着深远的影响,可以用织物张量来表征。为了将织物纳入临界状态理论(CST),有人提出了各向异性临界状态理论(ACST),将 CST 的状态参数 ((psi))修改为依赖于织物的膨胀状态参数 ((upzeta))。值得注意的是(uppsi)与宏观行为的特征(如不稳定性、相变和特征状态)有很强的相关性,因此,它已被许多构成模型所采用。虽然(upzeta)有助于将织物纳入 ACST 模型,但(upzeta)与特征特性之间的相关性尚未得到详细评估,尽管有大量关于微观力学和织物的研究。在这项研究中,对排水和非排水三轴进行了大量离散元法模拟,以评估(upzeta)与特征特性之间的相关性。为此,研究了重要特征(如不稳定性、相变和特征状态)中应力比与经典参数和膨胀状态参数((psi)和(upzeta))之间的相关性。结果发现,使用 (upzeta) 时这种相关性得到了改善,这可能是由于我们的模型中包含了织物。这一观察结果是新的,对于在构造模型中纳入织物演化具有重要意义。
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引用次数: 0
Effect of compression and shear on particle breakage of silica and calcareous sands 压缩和剪切对硅砂和石灰砂颗粒破碎的影响
IF 5.7 1区 工程技术 Q1 Earth and Planetary Sciences Pub Date : 2024-05-08 DOI: 10.1007/s11440-024-02339-3
Andrzej Głuchowski, Linzhu Li, Magued Iskander

Changes in particle granulometry could lead to significant changes in a soil’s behavior, making an understanding of micro-scale granulometry essential for practical applications. Changes in particle size, shape, and particle size distribution could result from a combination of applied normal and shearing stresses, which can in turn influence further response of the material. This study explored particle breakage during both compressive and shear loading under typical stresses. A deeper understanding of the phenomenon requires distinguishing broken and unbroken grains at the particle scale. Dynamic Image Analysis (DIA) was therefore employed to quantify changes in particle granulometry in two sands, a siliceous Ottawa sand and a calcareous sand known as Fiji Pink. Pre-sorted specimens having similar size, granulometry, and particle size distributions were tested using both oedometric and direct shear tests having the same aspect ratio, facilitating a direct comparison of the effects of shearing and compression on similar materials having different mineralogy. A breakage index was used for prognosis of particle breakage at key reference diameters. During oedometric tests, grain breakage was limited in both sands at stresses up to 1.2 MPa, but it increased significantly during direct shear tests. A conceptual model was proposed to explain the particle breakage mechanism during shear, at four key phase points representing (1) maximum compaction, (2) transition from compaction to dilative behavior, (3) maximum shear stress, and (4) peak test strain. In addition, a loading intensity framework was adopted to explain the relative roles of normal and shearing stresses on particle breakage. An increase of fines in soil during shearing was also observed and related to two sources: coarser grain abrasion and finer particle crushing. The vulnerability of grains with more anisotropic shapes was also observed. The loading intensity framework suggested that attrition of particle diameter could be divided into two phases, with a transitional critical loading intensity that appeared constant for each sand. For Ottawa sand, abrasion was the primary mechanism observed, causing a significant increase in Aspect Ratio (AR) and Sphericity (S) for finer grains. For Fiji sand, a transition from abrasion to attrition was noted, leading to limited sphericity decrease for the largest particles. Finer particles cushioning larger Fiji sand particles are more prone to breakage, resulting in increased AR and S. Finally, test results were used to propose a simple hyperbolic model to predict evolution of the particle size distribution during shear, for sands. The model was also verified using published data on grain evolution during shear of a different sand, not employed in its development.

颗粒粒度的变化会导致土壤行为的重大改变,因此了解微尺度粒度对实际应用至关重要。施加的法向应力和剪切应力会导致颗粒大小、形状和粒度分布发生变化,进而影响材料的进一步响应。本研究探讨了在典型应力下的压缩和剪切加载过程中的颗粒断裂现象。要深入了解这一现象,需要在颗粒尺度上区分断裂和未断裂的颗粒。因此,我们采用了动态图像分析法(DIA)来量化两种砂(一种是硅质渥太华砂,另一种是被称为 "斐济粉红 "的钙质砂)中颗粒粒度的变化。对具有相似尺寸、粒度和粒度分布的预分选出的试样,采用具有相同长径比的油压试验和直接剪切试验进行测试,以便直接比较剪切和压缩对具有不同矿物学性质的相似材料的影响。破损指数用于预测关键参考直径处的颗粒破损情况。在气压试验中,当应力达到 1.2 兆帕时,两种砂的颗粒破损都很有限,但在直接剪切试验中,颗粒破损明显增加。提出了一个概念模型来解释颗粒在剪切过程中的断裂机制,四个关键阶段点分别代表:(1)最大压实;(2)从压实到扩张行为的过渡;(3)最大剪切应力;以及(4)测试应变峰值。此外,还采用了加载强度框架来解释法向应力和剪切应力对颗粒破碎的相对作用。在剪切过程中还观察到土壤中细粒的增加,这与两个来源有关:较粗颗粒的磨损和较细颗粒的破碎。此外,还观察到形状各向异性较大的颗粒的脆弱性。加载强度框架表明,颗粒直径的损耗可分为两个阶段,每个砂的过渡临界加载强度似乎是恒定的。对于渥太华砂,磨损是观察到的主要机制,导致较细颗粒的长宽比(AR)和球形度(S)显著增加。对于斐济砂,观察到的是从磨损到损耗的过渡,导致最大颗粒的球形度有限下降。最后,试验结果被用来提出一个简单的双曲线模型,以预测砂在剪切过程中粒度分布的演变。该模型还利用已公布的另一种沙子在剪切过程中的粒度演变数据进行了验证,但该模型在开发过程中并未使用。
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引用次数: 0
DEM investigation on flow instability of particulate assemblies under coupling between volumetric and axial strains 体积应变和轴向应变耦合下颗粒组件流动不稳定性的 DEM 研究
IF 5.7 1区 工程技术 Q1 Earth and Planetary Sciences Pub Date : 2024-05-08 DOI: 10.1007/s11440-024-02331-x
M. Salimi, A. Lashkari, M. Tafili

The discrete element method (DEM) is employed to investigate the impact of coupling between volumetric and axial strains on the flow liquefaction vulnerability of 3D cubic particulate specimens. The virtual testing program conducted here encompasses a wide range of initial states and varying degrees of coupling between volumetric and axial strains. Utilizing data obtained from DEM simulations, the evolution of micro- and macroscale variables, including coordination number, contact fabric anisotropy, redundancy index, strong force networks, invariants of the effective stress tensor, and excess pore-water pressure, is examined. Results from DEM tests indicate that coupling expansive volumetric strain with axial strain leads to a gradual loosening of the load bearing microstructure, a decrease in coordination number, and a faster change in contact anisotropy. DEM simulations demonstrate that the triggering of flow liquefaction instability is followed by a sudden increase in contact fabric anisotropy and abrupt drops in coordination number and redundancy index. Moreover, a detailed analysis of the findings suggests that the stress ratio at the onset of post-peak softening decreases with increasing expansive volumetric strains.

本文采用离散元素法(DEM)研究了体积应变和轴向应变之间的耦合对三维立方颗粒试样流动液化脆弱性的影响。这里进行的虚拟测试程序包括多种初始状态以及体积应变和轴向应变之间不同程度的耦合。利用从 DEM 模拟中获得的数据,研究了微观和宏观变量的演变,包括配位数、接触织物各向异性、冗余指数、强力网络、有效应力张量不变量和过剩孔隙水压力。DEM 试验结果表明,膨胀性体积应变与轴向应变的耦合会导致承载微观结构的逐渐松动、配位数的减少以及接触各向异性的快速变化。DEM 模拟表明,在触发流动液化不稳定性后,接触织物各向异性会突然增加,配位数和冗余指数会突然下降。此外,对研究结果的详细分析表明,峰后软化开始时的应力比会随着膨胀体积应变的增加而减小。
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引用次数: 0
Influence of wetting and drying cycles on the shear behavior of discontinuities between two different rock types with various surface topographies 湿润和干燥循环对具有不同表面形貌的两种不同类型岩石之间不连续面的剪切行为的影响
IF 5.7 1区 工程技术 Q1 Earth and Planetary Sciences Pub Date : 2024-05-06 DOI: 10.1007/s11440-024-02332-w
Qiong Wu, Yue Qin, Huiming Tang, Zhen Meng, Changdong Li, Sha Lu

Wetting and drying cycles (WDCs) have a significant impact on the shear behavior of discontinuities with different joint wall materials (DDJMs). This influence is crucial for the reasonable evaluation of the long-term stability of soft and hard interbedded rock slopes under water level fluctuations. As the surface topographies of natural discontinuities collected from the field vary, conducting comparative experiments on natural discontinuity specimens with identical surface topographies is challenging. To solve this problem, a 3D surface topography reconstruction technique was employed to obtain DDJM specimens with three types of surface topographies collected from a typical sliding-prone stratum in the Three Gorges Reservoir area, China. A series of experiments, including computed tomography scanning, 3D laser scanning, and direct shear tests, were conducted to investigate the influence of WDCs on the micro- and macroproperties of joint walls, surface topographies, and shear behavior of DDJMs. The experimental results showed that repeated WDC treatments caused the degradation of the microstructures and macroscopic physical properties of the studied joint walls, and the more severely weakened joint wall played a predominant role in reducing the shear strength of DDJMs. The influence of WDCs on the surface topographies of DDJMs was negligible in this study; changes in the shear behavior of DDJMs were closely associated with the weakening of joint walls induced by WDCs; and the impact degree of joint wall weakening on the deterioration of the shear behavior of DDJMs was interactively influenced by and positively correlated with both the joint roughness coefficient and normal stress. These results will contribute to a better understanding of the evolution of the stability of soft and hard interbedded rock slopes induced by water level fluctuations in the Three Gorges Reservoir area and other reservoir regions.

湿润和干燥周期(WDCs)对采用不同接壁材料(DDJMs)的不连续面的剪切行为有重大影响。这种影响对于合理评估软硬夹层岩石边坡在水位波动下的长期稳定性至关重要。由于从野外采集的天然不连续面的表面形貌各不相同,因此在具有相同表面形貌的天然不连续面试样上进行对比实验具有挑战性。为了解决这个问题,我们采用了三维表面形貌重建技术,从中国三峡库区典型的易滑动地层中采集到三种表面形貌的 DDJM 试样。在本研究中,WDC 对 DDJM 表面形貌的影响可以忽略不计;DDJM 剪切行为的变化与 WDC 引起的接合壁削弱密切相关;接合壁削弱对 DDJM 剪切行为恶化的影响程度受接合粗糙度系数和法向应力的交互影响,并与之呈正相关。这些结果将有助于更好地理解三峡库区及其他库区水位波动诱发的软硬夹层岩质边坡稳定性的演变过程。
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引用次数: 0
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