Soils and Foundations最新文献_第2页

Soil compaction control by monitoring compacted states based on soil stiffness indices 基于土体刚度指标监测压实状态的土壤压实控制

IF 3.3 2区工程技术 Q2 ENGINEERING, GEOLOGICAL

Soils and Foundations

Pub Date : 2026-01-02 DOI: 10.1016/j.sandf.2025.101709

F. Tatsuoka , T. Yoshida , H. Nagai , Y. Tomita , R. Latimer , Y. Kikuchi , J. Koseki

A number of empirical equations, expressing the various types of soil stiffness indices (SSIs) of compacted soil as functions of dry density ρ_d and degree of saturation S_r, are summarized in this study. They are generalized in the normalized form of SSI= C_SSI·F_SSI(ΔS_r)·G_SSI([D_c]_1Ec). C_SSI is the coefficient, different for different SSI test conditions, F_SSI(ΔS_r) is a decreasing function of ΔS_r= S_r – “the optimum, (S_r)_opt” with F_SSI(ΔS_r = 0) = 1.0, and G_SSI([D_c]_1Ec) is an increasing function of the degree of compaction by the Standard Proctor test, [D_c]_1Ec, with G_SSI([D_c]_1Ec = 100 %) = 1.0. Under the various conditions of the data, the G_SSI functions are rather similar, whereas the F_SSI functions are largely different. With drained SSIs evaluated at relatively low strains and relatively low confining pressures, F_SSI is considerably large when ΔS_r < 0 due to the fairly large effects of S_r on these SSIs. As a result, when S_r is in a certain range just below (S_r)_opt, the SSIs become the effective indices of water content w, rather than ρ_d. The compacted water content can be estimated and controlled to remain within a narrow range centered at the target by keeping the frequently measured field SSIs between the defined upper and lower thresholds. The procedure for determining the target and the upper and lower bounds of the SSIs, based on field calibration compaction test data and relevant normalized empirical SSI equations, is explained. A simplified method is proposed, which suggests that, when field SSIs are kept between 0.5 and 2.0 times the target SSI, compacted w values are expected to be approximately maintained between 0.8 and 1.2 times the target w.

本文总结了各种类型的压实土刚度指数（ssi）随干密度ρd和饱和度Sr的函数的经验方程。它们的归一化形式为SSI= CSSI·FSSI（ΔSr）·GSSI（[Dc]1Ec）。CSSI是系数，对于不同的SSI测试条件不同，FSSI（ΔSr）是ΔSr= Sr -“最优，（Sr）opt”的递减函数，FSSI（ΔSr = 0） = 1.0， GSSI（[Dc]1Ec）是标准Proctor测试的压实度的递增函数，[Dc]1Ec， GSSI([Dc]1Ec = 100%) = 1.0。在不同的数据条件下，GSSI函数非常相似，而FSSI函数差异很大。在相对低应变和相对低围压条件下，由于Sr对ssi的影响较大，在ΔSr <； 0时，FSSI相当大。因此，当Sr在刚好低于（Sr）opt的一定范围内时，ssi成为表征含水率w的有效指标，而不是ρd。通过将频繁测量的场ssi保持在定义的上限和下限之间，可以估计和控制压实水含量，使其保持在以目标为中心的狭窄范围内。说明了基于现场标定压实试验数据和相关归一化经验SSI方程确定SSI目标和上下界的过程。提出了一种简化方法，该方法表明，当字段SSI保持在目标SSI的0.5 ~ 2.0倍之间时，预计压缩w值将大致保持在目标w的0.8 ~ 1.2倍之间。

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引用次数: 0

Drainage and imbibition along main and scanning curves: A pore-scale morphology approach 沿主曲线和扫描曲线的排水和渗吸：一种孔隙尺度的形态学方法

IF 3.3 2区工程技术 Q2 ENGINEERING, GEOLOGICAL

Soils and Foundations

Pub Date : 2025-12-31 DOI: 10.1016/j.sandf.2025.101722

Shizuka Eshiro, Shuta Fuchisaki, Yosuke Higo

This study quantifies the three-dimensional morphologies of pore air and pore water, and examines drainage and imbibition behaviours along main and scanning curves in water retention tests. The aim was to clarify the pore-scale drainage and imbibition mechanisms and their relationships to specimen-scale water distribution patterns. The water retention tests involved two drying and wetting cycles, during which X-ray micro-computed tomography (CT) imaging was performed at each equilibrium point. From segmented CT images, pore air and pore water clusters, as well as drainage and imbibition clusters, were extracted and analysed. The cluster volume distributions, number of clusters, and continuity of the pore air and pore water phases were evaluated, revealing distinct transitions of water distribution patterns that depend on the degree of saturation and the drying–wetting history. The shape complexity and spatial positions of the drainage and imbibition clusters were evaluated, and the drainage and imbibition mechanisms along the main and scanning curves were identified. Five distinct saturation regimes were defined based on phase continuity, which were linked to the complexity of the drainage and imbibition cluster shapes. These findings offer insights into the pore-scale mechanisms that underlie macroscopic water retention behaviour and provide implications for improving theoretical water retention curve models.

本研究量化了孔隙空气和孔隙水的三维形态，并考察了持水试验中沿主曲线和扫描曲线的排水和吸胀行为。目的是澄清孔隙尺度的排水和吸胀机制及其与样品尺度水分布模式的关系。水保持试验包括两个干燥和湿润循环，在此期间，在每个平衡点进行x射线微计算机断层扫描（CT）成像。从分割的CT图像中提取并分析孔隙空气和孔隙水团簇，以及排水和吸胀团簇。对孔隙气相和孔隙水相的团簇体积分布、团簇数量和连续性进行了评估，揭示了水分布模式的明显转变，这取决于饱和度和干湿历史。评价了排吸组团的形状复杂性和空间位置，确定了主曲线和扫描曲线上的排吸机理。根据相连续性定义了五种不同的饱和状态，这与排水和吸胀团簇形状的复杂性有关。这些发现为宏观保水行为背后的孔隙尺度机制提供了见解，并为改进理论保水曲线模型提供了启示。

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引用次数: 0

Effects of specimen preparation methods on polymer–montmorillonite interactions and hydraulic conductivity of polymer-modified bentonite–sand mixtures 试样制备方法对聚合物-蒙脱土相互作用及聚合物改性膨润土-砂混合料水导率的影响

IF 3.3 2区工程技术 Q2 ENGINEERING, GEOLOGICAL

Soils and Foundations

Pub Date : 2025-12-22 DOI: 10.1016/j.sandf.2025.101711

Qingyuan Zhao , Kunlin Ruan , Daichi Ito , Guodong Cai , Hao Wang , Hideo Komine

In this study, carboxymethylcellulose (CMC) was used to modify bentonite (PMB) via wet blending (WB) and dry blending (DB) methods and then polymer-modified bentonite–sand mixtures (PMBSM) were produced based on PMB. Free swell index and hydraulic conductivity (k) tests were conducted on these specimens. Several experiments, including X-ray diffraction (XRD), cation exchangeable capacity (CEC) and Fourier transform infrared spectroscopy (FTIR) were used to elucidate how polymer interacted with montmorillonite for different preparation methods. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) tests were used to elucidate the PMBSM microfabric characteristics. Swell index results indicated higher swelling potential of WB-PMB than that of DB-PMB. XRD, CEC, and FTIR test results suggested that polymer intercalation between montmorillonite layers props interlayer spacing for WB-PMB. DB-PMB had a phase-separated interaction by which polymer chains did not interact with montmorillonite. Hydraulic conductivity tests indicated that low k, approximately 10 times lower than BSM, was maintained by DB-PMBSM for all bentonite contents (Bc). By contrast, WB-PMBSM and BSM had similar k under low Bc conditions (10 %). However, when the Bc increased to 30 %, WB-PMBSM exhibited lower k than either BSM and DB-PMBSM, suggesting that different mechanisms control k of WB and DB-PMBSM. Conceptual models were proposed, relating the interaction mechanism and hydraulic performance of PMBSM.

本研究以羧甲基纤维素（CMC）为原料，通过湿共混（WB）和干共混（DB）两种方法对膨润土（PMB）进行改性，在此基础上制备聚合物改性膨润土-砂混合物（PMBSM）。对试件进行了自由膨胀指数和导水系数(k)试验。利用x射线衍射（XRD）、阳离子交换容量（CEC）和傅里叶变换红外光谱（FTIR）等实验研究了不同制备方法下聚合物与蒙脱土的相互作用。采用扫描电子显微镜（SEM）和能谱仪（EDS）对PMBSM微织物进行了表征。肿胀指数结果显示，WB-PMB的肿胀电位高于DB-PMB。XRD、CEC和FTIR测试结果表明，聚合物在蒙脱土层间的嵌层作用促进了WB-PMB的层间间距。DB-PMB具有相分离相互作用，聚合物链不与蒙脱土相互作用。水导率测试表明，在所有膨润土含量（Bc）下，DB-PMBSM均保持较低的k值，约为BSM的10倍。相比之下，WB-PMBSM和BSM在低Bc条件下具有相似的k（10%）。然而，当Bc增加到30%时，WB- pmbsm的k值低于BSM和DB-PMBSM，这表明WB和DB-PMBSM的k值控制机制不同。提出了PMBSM相互作用机理和水力性能的概念模型。

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引用次数: 0

Observed performances and spatial effects of a set of 40 m ultra-deep rectangular excavations in Shanghai soft soils 上海软土中一组40 m超深矩形基坑的性能及空间效应

IF 3.3 2区工程技术 Q2 ENGINEERING, GEOLOGICAL

Soils and Foundations

Pub Date : 2025-12-18 DOI: 10.1016/j.sandf.2025.101710

Yinhang Zhu , Weidong Wang , Zhonghua Xu , Jinjian Chen , Zhihao Yang

The accelerating development of deep excavations in urban environment has garnered much attention on the excavation-induced deformations and environmental impacts. This paper presents a set of five ultra-deep rectangular excavations with the depth of 39.31–45.45 m in Shanghai soft soils. An extensive monitoring program was conducted to record excavation-induced deformation and influence on the surroundings. The spatial effect of rectangular excavations was further discussed. Based on the analyses of the observed performances of the excavations, the key findings are as follows: (1) The maximum lateral deflections of the diaphragm walls δ_hmax were about 0.10–0.55 % of the excavation depths H_e at the end of construction, and significant spatial and temporal effects in δ_h were observed. (2) The maximum ground settlement, δ_vmax, was generally within 0.65 % H_e, appearing at the distance of around 0.5 H_e outside the pits. (3) The spatial effect was more obvious in narrow excavations in this study. (4) Smaller normalized excavation scales led to smaller normalized wall deflections, emphasizing the confining effect of excavations’ geometry. The measured performances of the deepest rectangular excavations in Shanghai soft soil and observed spatial effects can serve as a valuable reference for the design and research of future ultra-deep excavations.

随着城市环境中深基坑工程的加速发展，开挖引起的变形及其对环境的影响日益受到人们的关注。本文在上海软土中设计了5组超深矩形基坑，开挖深度为39.31 ~ 45.45 m。进行了广泛的监测程序，以记录开挖引起的变形及其对周围环境的影响。进一步讨论了矩形开挖的空间效应。结果表明：(1)施工结束时连续墙最大侧移δhmax约为开挖深度He的0.10 ~ 0.55%，且δh具有显著的时空效应；(2)地表沉降最大值δvmax一般在0.65% He以内，出现在坑外0.5 He左右。(3)空间效应在狭窄的基坑中更为明显。(4)归一化开挖规模越小，归一化墙体挠度越小，强调了开挖几何形状的约束作用。上海软土地基中最深矩形基坑的实测性能及观测到的空间效应可为今后超深基坑的设计与研究提供有价值的参考。

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引用次数: 0

Unified pseudo-static seismic reduction factors for shallow foundations via an earth-pressure framework 基于土压力框架的浅基础统一拟静力减震系数

IF 3.3 2区工程技术 Q2 ENGINEERING, GEOLOGICAL

Soils and Foundations

Pub Date : 2025-12-15 DOI: 10.1016/j.sandf.2025.101713

Lysandros Pantelidis

This paper presents a unified and physically consistent method for evaluating the seismic bearing capacity of shallow foundations, based on classical earth pressure theory and a reinterpretation of the failure mechanism beneath the footing. The method builds on the key observation that the failure surface forms an angle of

45^{°} + φ / 2

with the footing (Zone I) and exits at

45^{°} - φ / 2

(Zone III), consistent with the geometry of active and passive earth pressures. Central to the analysis is the concept of a “virtual wall” extending downward from the footing edge to the log-spiral segment (Zone II) of the failure surface. Under seismic loading, the effective height of this virtual wall is reduced to account for the shallower failure mechanism. The framework is rigorously calibrated against the finite element method, in which the models are deliberately extended and lateral boundaries sloped on the failure side to prevent artificial reflection of seismic stresses. A distinctive feature of the proposed methodology is that all seismic reduction factors—cohesion, surcharge, and self-weight—are derived in a unified manner from a single physical mechanism. The resulting expressions are valid for any

c - φ

soil, and apply to both effective and total stress analyses. The reduction factors in the classical three N-bearing capacity formula are given as

ε_{c} = ε_{q}

=

ε_{H}

,

ε_{γ} = ε_{H}^{2}

, with

{ε_{H} = (1 - k_{h} / (t a n φ + c / γ H_{\max}))}^{0.2}

, where

H_{\max}

is the maximum depth of the failure mechanism. The method also incorporates the effects of structure inertia using a set of inclination factors previously developed by the author, ensuring compatibility with practical design practice. By linking seismic effects directly to modifications of the classical bearing-capacity terms, the method provides engineers with a transparent, physically based, and easily applicable tool for design-level seismic assessments of shallow foundations.

本文基于经典土压力理论和对基础下破坏机制的重新解释，提出了一种统一的、物理一致的浅基础抗震承载力评价方法。该方法建立在关键观测的基础上，即破坏面与基础形成45°+φ/2角（I区），并以45°-φ/2角（III区）退出，与主动和被动土压力的几何形状一致。分析的核心是“虚拟墙”的概念，从基础边缘向下延伸到破坏面的对数螺旋段（II区）。在地震荷载作用下，考虑到较浅的破坏机制，降低了虚拟墙的有效高度。该框架是根据有限元方法严格校准的，在有限元方法中，模型被故意扩展，横向边界在破坏侧倾斜，以防止人为反射地震应力。所提出方法的一个显著特点是，所有的减震因子——内聚力、附加量和自重——都以统一的方式从单一的物理机制中推导出来。所得表达式适用于任何c-φ土，并适用于有效应力和总应力分析。经典三氮承载力公式中的折减系数为εc=εq=εH, εγ=εH2, εH=1-kh/(tanφ+c/γHmax)0.2，其中Hmax为破坏机制的最大深度。该方法还利用作者先前开发的一组倾斜因素纳入了结构惯性的影响，确保了与实际设计实践的兼容性。通过将地震效应直接与经典承载力条款的修改联系起来，该方法为工程师提供了一个透明的、基于物理的、易于应用的工具，用于浅基础的设计级地震评估。

{"title":"Unified pseudo-static seismic reduction factors for shallow foundations via an earth-pressure framework","authors":"Lysandros Pantelidis","doi":"10.1016/j.sandf.2025.101713","DOIUrl":"10.1016/j.sandf.2025.101713","url":null,"abstract":"<div><div>This paper presents a unified and physically consistent method for evaluating the seismic bearing capacity of shallow foundations, based on classical earth pressure theory and a reinterpretation of the failure mechanism beneath the footing. The method builds on the key observation that the failure surface forms an angle of <math><mrow><msup><mn>45</mn><mo>°</mo></msup><mo>+</mo><mspace></mspace><mi>φ</mi><mo>/</mo><mn>2</mn></mrow></math> with the footing (Zone I) and exits at <math><mrow><msup><mn>45</mn><mo>°</mo></msup><mo>-</mo><mspace></mspace><mi>φ</mi><mo>/</mo><mn>2</mn></mrow></math> (Zone III), consistent with the geometry of active and passive earth pressures. Central to the analysis is the concept of a “virtual wall” extending downward from the footing edge to the log-spiral segment (Zone II) of the failure surface. Under seismic loading, the effective height of this virtual wall is reduced to account for the shallower failure mechanism. The framework is rigorously calibrated against the finite element method, in which the models are deliberately extended and lateral boundaries sloped on the failure side to prevent artificial reflection of seismic stresses. A distinctive feature of the proposed methodology is that all seismic reduction factors—cohesion, surcharge, and self-weight—are derived in a unified manner from a single physical mechanism. The resulting expressions are valid for any <math><mrow><mi>c</mi><mo>-</mo><mi>φ</mi></mrow></math> soil, and apply to both effective and total stress analyses. The reduction factors in the classical three N-bearing capacity formula are given as <math><mrow><msub><mi>ε</mi><mi>c</mi></msub><mo>=</mo><msub><mi>ε</mi><mi>q</mi></msub></mrow></math>=<math><msub><mi>ε</mi><mi>H</mi></msub></math>, <math><mrow><msub><mi>ε</mi><mi>γ</mi></msub><mo>=</mo><msubsup><mi>ε</mi><mrow><mi>H</mi></mrow><mn>2</mn></msubsup></mrow></math>, with <math><msup><mrow><msub><mi>ε</mi><mi>H</mi></msub><mo>=</mo><mfenced><mrow><mn>1</mn><mo>-</mo><msub><mi>k</mi><mi>h</mi></msub><mo>/</mo><mrow><mo>(</mo><mi>t</mi><mi>a</mi><mi>n</mi><mi>φ</mi><mo>+</mo><mi>c</mi><mo>/</mo><mi>γ</mi><msub><mi>H</mi><mrow><mi>max</mi></mrow></msub><mo>)</mo></mrow></mrow></mfenced></mrow><mrow><mn>0.2</mn></mrow></msup></math>, where <math><msub><mi>H</mi><mrow><mi>max</mi></mrow></msub></math> is the maximum depth of the failure mechanism. The method also incorporates the effects of structure inertia using a set of inclination factors previously developed by the author, ensuring compatibility with practical design practice. By linking seismic effects directly to modifications of the classical bearing-capacity terms, the method provides engineers with a transparent, physically based, and easily applicable tool for design-level seismic assessments of shallow foundations.</div></div>","PeriodicalId":21857,"journal":{"name":"Soils and Foundations","volume":"66 1","pages":"Article 101713"},"PeriodicalIF":3.3,"publicationDate":"2025-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145791660","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Improved analysis method for frame beams with prestressed cables in slopes based on inclined foundation stiffness 基于倾斜基础刚度的坡面预应力索框架梁改进分析方法

IF 3.3 2区工程技术 Q2 ENGINEERING, GEOLOGICAL

Soils and Foundations

Pub Date : 2025-12-13 DOI: 10.1016/j.sandf.2025.101712

Yuan Qi , Shiguo Xiao , Tianxiang Liu

The frame beam with prestressed cables is a reinforcement structure to stabilize slopes or landslides, where the frame beam is placed on the slope face. Since the inclined foundation for the beam is different from the level one, it is crucial to determine reasonable normal stiffness of slope foundations to analyze mechanical responses of the frame beam under the cable tensioning forces. According to the upper-bound limit analysis theory, an analysis method for the ultimate bearing capacity of strip foundation on the slope face is provided based on a bilateral failure mechanism. The inclined foundation stiffness is accordingly expressed as the level one multiplied by the ratio of the inclined over the level bearing capacity. Further, a calculation method for the frame beam is established based on static equilibrium and deformation compatibility of the intersected elements in the frame as beams on the inclined elastic foundation. Some in-situ tests indicate the proposed inclined foundation stiffness is about 16 % smaller than the observed result. Compared with the classic level-foundation method for the frame beam, the improved method is closer to the numerical simulations. The ratio of the inclined over the level foundation stiffness is nonlinearly decreasing clearly from 1 as the slope angle increases from 0°. The stiffness ratio reduces with the increase of the soil unit weight, internal friction angle, and beam width, while increases with the cohesion and beam-soil friction angle. The mid-span bending moment and deflection of each element in the frame increases nonlinearly with the slope angle, whereas the shear force is faintly influenced by the slope angle.

带预应力索的框架梁是一种用于稳定边坡或滑坡的加固结构，框架梁置于坡面上。由于梁的倾斜基础与水平基础不同，确定合理的边坡基础法向刚度是分析框架梁在索拉力作用下的力学响应的关键。根据上限分析理论，提出了一种基于双侧破坏机制的边坡面条形基础极限承载力分析方法。因此，倾斜基础刚度表示为水平1乘以倾斜与水平承载力之比。在此基础上，建立了基于框架内相交单元作为倾斜弹性基础梁的静力平衡和变形协调的框架梁计算方法。一些现场试验表明，所提出的倾斜基础刚度比观测结果小16%左右。与传统的框架梁水平基础法相比，改进后的方法更接近数值模拟结果。随着坡角从0°开始增大，倾斜与水平基础刚度之比从1开始呈明显的非线性递减。刚度比随土体单位重、内摩擦角和梁宽的增大而减小，随黏聚力和梁土摩擦角的增大而增大。框架内各单元跨中弯矩和挠度随坡角呈非线性增加，而剪力受坡角影响不大。

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引用次数: 0

Large-area slope stability analysis: Performance comparison of three-dimensional limit equilibrium methods 大面积边坡稳定性分析：三维极限平衡法的性能比较

IF 3.3 2区工程技术 Q2 ENGINEERING, GEOLOGICAL

Soils and Foundations

Pub Date : 2025-11-10 DOI: 10.1016/j.sandf.2025.101703

Daichi Sugo , John Y. Choe , Saneiki Fujita , Nilo Lemuel J. Dolojan , Kenta Tozato , Reika Nomura , Kenjiro Terada , Eiji Tominaga , Shoji Iwanaga , Shuji Moriguchi

3D limit equilibrium methods (LEMs) for assessing slope stability over large areas have been applied in some studies (e.g., Tran et al., 2018; He et al., 2018). However, their use remains limited compared to computationally cheaper alternatives (e.g., statistical or simple physics-based models) due to higher computational demands and the fact that their practical accuracy has not been sufficiently examined. In addition, while the Hovland method is recognized as the most computationally efficient 3D LEM, its accuracy has been questioned (e.g., Azzouz and Baligh (1978); Hutchinson and Sarma (1985)), which has further hindered the broader adoption of 3D LEMs. This study compares three well-established 3D LEMs. It first compares the characteristics of these methods under simple slope conditions. Then, the comparison is extended to a large area with numerous slopes, considering actual terrain data and a heavy rainfall event. The findings reveal variations in factor-of-safety values across methods. However, receiver operating characteristic curve indicated no significant differences between their accuracies in predicting the actual landslide distribution. This suggests that the Hovland method, boasting the lowest computational cost (e.g., under 50 min) among the methods, can effectively pinpoint high-risk areas identified by the other methods (e.g., over 7 h) by simply adjusting the factor-of-safety threshold. To further generalize these findings, future work should additionally consider highly variable and complex inputs, such as the spatial distribution of groundwater tables.

用于评估大面积边坡稳定性的3D极限平衡方法（LEMs）已在一些研究中得到应用（例如，Tran等人，2018；He等人，2018）。然而，与计算成本更低的替代方案（例如，统计或简单的基于物理的模型）相比，它们的使用仍然有限，因为计算需求更高，而且它们的实际准确性尚未得到充分检验。此外，虽然Hovland方法被认为是计算效率最高的3D LEM，但其准确性受到质疑(例如，Azzouz和Baligh (1978)；Hutchinson和Sarma(1985))，这进一步阻碍了3D lem的广泛采用。本研究比较了三种成熟的3D lem。首先比较了这些方法在简单边坡条件下的特点。然后，考虑到实际地形数据和强降雨事件，将比较扩展到具有众多斜坡的大面积区域。研究结果揭示了不同方法的安全系数值的差异。然而，在预测实际滑坡分布时，接收方工作特征曲线显示两者的精度没有显著差异。这表明，计算成本最低（例如，在50 min以下）的Hovland方法可以通过简单地调整安全系数阈值，有效地确定由其他方法（例如，超过7 h）识别的高风险区域。为了进一步推广这些发现，未来的工作应额外考虑高度可变和复杂的输入，如地下水位的空间分布。

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引用次数: 0

Microscopic investigation into density dependence of water retention characteristics of sand during drying-wetting process 干湿过程中砂土保水特性密度依赖性的微观研究

IF 3.3 2区工程技术 Q2 ENGINEERING, GEOLOGICAL

Soils and Foundations

Pub Date : 2025-11-07 DOI: 10.1016/j.sandf.2025.101704

Ryunosuke Kido , Yosuke Higo , Shizuka Eshiro

The density dependence of the water retention characteristics of sand during the drying-wetting process was microscopically investigated. Water retention tests on both loose sand and dense sand were conducted with X-ray micro computed tomography (CT). The frequency distributions of the local porosity and degree of saturation within each sand specimen, the principal curvature of the air–water interface, and the volume distribution of pore water were analyzed using image processing techniques. The microscopic observations revealed that the density dependence of the water retention characteristics during the drying-wetting process primarily lies in the morphology of the pore water, the number of pore water clusters, and the volume distributions of the pore water clusters. The types of distributions of the local degrees of saturation and the volume distributions of the pore water clusters within the sands remained similar despite the drying-wetting history, and were found to be independent of the sand density. The present study confirmed the essential factors of the density dependence of the water retention characteristics which have been conceptually interpreted. The findings will surely contribute to the development of a theoretical model for water retention curves considering the porosity and particle size distribution based on an explicit mechanism, offering an alternative to conventional models (e.g., the van Genuchten model) that empirically consider the effects of porosity on water retention curves.

微观研究了干湿过程中砂土保水特性的密度依赖性。采用x射线微计算机断层扫描（CT）对松散砂和致密砂进行了保水性试验。利用图像处理技术分析了各砂体内部局部孔隙度和饱和度的频率分布、气-水界面的主曲率以及孔隙水的体积分布。微观观察结果表明，干湿过程中水保持特性的密度依赖性主要在于孔隙水的形态、孔隙水团簇的数量和孔隙水团簇的体积分布。在干湿交替过程中，孔隙水团簇的局部饱和度分布类型和体积分布类型基本一致，且与砂体密度无关。本研究证实了密度对保水特性依赖的基本因素，这些因素在概念上得到了解释。研究结果将有助于建立基于明确机制的考虑孔隙度和粒径分布的持水曲线理论模型，为经验考虑孔隙度对持水曲线影响的传统模型（如van Genuchten模型）提供一种替代方案。

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引用次数: 0

Microstructural characterisation of foam-induced porosity in lightweight cemented soils using X-ray micro-tomography 用x射线微层析成像技术表征轻质胶结土泡沫孔隙的微观结构

IF 3.3 2区工程技术 Q2 ENGINEERING, GEOLOGICAL

Soils and Foundations

Pub Date : 2025-11-06 DOI: 10.1016/j.sandf.2025.101706

F. Ferriero , L. Perrotta , L. Pappalardo , G. Buono , E. Vitale , G. Russo

Lightweight Cemented Soils (LWCS), produced by mixing natural soil, water, cement and air foam, are characterised by high workability, good mechanical properties and reduced unit weight. Their microstructure is complex and consists of large foam-induced voids embedded within a cemented porous matrix. The matrix has been recently studied, whereas there is a lack of knowledge about the distribution, size and stability of foam-induced voids during the chemo-physical evolution of the system. In this study, a novel microstructural investigation has been developed by performing X-ray microtomography on LWCS samples lightened with 40 % of foam at increasing curing time. The use of this technique allows quantitative analysis on the evolution of the foam-induced voids, not achievable by other conventional experimental techniques (e.g., Mercury Intrusion Porosimetry). Image analysis of X-ray microtomography scans shows that the foam-induced porosity remains stable (i.e., without collapse or coalescence) over curing time, whereas shrinkage fractures due to cement hydration lead to a slight increase of the porosity. Moreover, the frequency of largest voids decreases slightly due to precipitation of new compounds. The hydraulic conductivity of LWCS is estimated for the first time through a Pore Network Model, based on the real microstructure of the material, obtained from X-ray microtomography scans. The computed hydraulic conductivity is compared with the permeability of the matrix (i.e. cemented sample without foam) derived from Mercury Intrusion Porosimetry test and with the hydraulic conductivity estimated from experimental tests. The numerical result shows a good agreement with the experimental data (the values are of the same order of magnitude i.e., 10⁻¹⁰ m/s), highlighting that, for the considered foam content, hydraulic conductivity of LWCS is primarily controlled by the permeability of the matrix, as air voids and shrinkage fractures are isolated and accessible only through the matrix.

轻质胶结土（LWCS）是由天然土壤、水、水泥和空气泡沫混合而成，具有可加工性高、力学性能好、单位重量轻等特点。它们的微观结构复杂，由嵌入在胶结多孔基质中的大泡沫诱导空隙组成。近年来，人们对基质进行了研究，但在体系的化学物理演化过程中，人们对泡沫诱导空洞的分布、大小和稳定性缺乏了解。在这项研究中，通过对添加40%泡沫的LWCS样品在增加固化时间下进行x射线显微断层扫描，开发了一种新的微观结构研究。使用该技术可以定量分析泡沫诱导空洞的演变，这是其他传统实验技术（例如汞侵入孔隙法）无法实现的。x射线微断层扫描图像分析显示，在固化过程中，泡沫诱导的孔隙度保持稳定（即没有坍塌或聚结），而水泥水化导致的收缩裂缝会导致孔隙度略有增加。此外，由于新化合物的析出，最大空洞的频率略有降低。通过基于x射线显微断层扫描获得的材料真实微观结构的孔隙网络模型，首次估算了LWCS的水力导电性。将计算得到的水力导率与压汞孔隙法测试得到的基质（即无泡沫胶结试样）的渗透率以及实验测试估计的水力导率进行比较。数值结果与实验数据吻合较好（数值均为10 ~ 10m /s），说明在考虑泡沫含量的情况下，LWCS的导流率主要受基质渗透率的控制，孔隙和收缩裂缝是隔离的，只能通过基质进入。

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引用次数: 0

Field investigation of steel screw micropiles under axial loads in cohesionless and cohesive soils 无黏性和粘性土中轴向荷载作用下钢螺纹微桩的现场研究

IF 3.3 2区工程技术 Q2 ENGINEERING, GEOLOGICAL

Soils and Foundations

Pub Date : 2025-10-30 DOI: 10.1016/j.sandf.2025.101705

João Batista de Oliveira Libório Dourado , Lijun Deng

Steel screw micropiles are a new pile type for light load applications or building remediation, offering several advantages over conventional concrete piles. Unique feature of screw micropile shafts requires distinctive design approaches; despite the growing use, there is limited field measured data on their axial failure or torque-based design. This study aims to evaluate the ultimate capacity of screw micropiles, analyze the axial failure mode, develop empirical correlations between installation torque and ultimate capacity, and refine a torque estimation method based on Cone Penetration Tests (CPT). Full-scale axial compression tests in both cohesionless and cohesive soils were performed on five screw micropile types with diameters ranging from 76 mm to 114 mm and lengths from 1.6 m to 3.0 m. Each test was repeated three times, totalling 30 tests. In-situ and laboratory investigations were conducted to characterize the soils. Results showed that in cohesionless soil, installation torque increased linearly with depth; while in cohesive soil, torque tended to stabilize after the threaded segment was fully embedded. The evidence suggests the impact of soil strength and disturbance on installation torque. A reliable linear relationship was observed between installation torque and ultimate capacities, with torque factors (defined as the ratio of pile ultimate capacity to max installation torque) ranging from 21.5 to 27.8 m⁻¹. Back-analysis suggested that the axial failure is governed by local bearing beneath each thread. The CPT-based torque estimation method in previous studies for piles in cohesive soil was revised to include the effect of smooth segment, and the revised method suggested consistent comparison with the measured torque.

钢螺旋微桩是一种用于轻载应用或建筑修复的新型桩型，与传统的混凝土桩相比具有许多优点。螺旋微桩桩身的独特特点要求其设计方法与众不同；尽管使用越来越多，但关于轴向失效或基于扭矩的设计的现场测量数据有限。本研究旨在评估螺旋微桩的极限承载力，分析轴向破坏模式，建立安装扭矩与极限承载力的经验相关性，并完善基于锥贯入试验（CPT）的扭矩估计方法。采用直径为76 mm ~ 114 mm、长度为1.6 m ~ 3.0 m的5种螺纹微桩进行了无黏性和粘性土的全尺寸轴压试验。每个试验重复3次，共30次。进行了现场和实验室调查，以表征土壤。结果表明：在无黏性土中，安装扭矩随深度线性增加；而在粘性土中，螺纹段完全嵌入后，扭矩趋于稳定。有证据表明，土的强度和扰动对安装扭矩的影响。安装扭矩与极限承载力之间存在可靠的线性关系，扭矩因子（定义为桩的极限承载力与最大安装扭矩的比值）在21.5 ~ 27.8 m−1之间。反分析表明轴向破坏是由每根螺纹下的局部轴承控制的。对以往研究中基于cpt的粘性土中桩的扭矩估计方法进行了修正，加入了光滑段的影响，修正后的方法与实测扭矩比较一致。

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引用次数: 0