Pub Date : 2025-12-22DOI: 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.
{"title":"Effects of specimen preparation methods on polymer–montmorillonite interactions and hydraulic conductivity of polymer-modified bentonite–sand mixtures","authors":"Qingyuan Zhao , Kunlin Ruan , Daichi Ito , Guodong Cai , Hao Wang , Hideo Komine","doi":"10.1016/j.sandf.2025.101711","DOIUrl":"10.1016/j.sandf.2025.101711","url":null,"abstract":"<div><div>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 (<em>k</em>) tests were conducted on these specimens. Several experiments, including X-ray diffraction (XRD), cation exchangeable capacity (<em>CEC</em>) 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, <em>CEC</em>, 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 <em>k</em>, approximately 10 times lower than BSM, was maintained by DB-PMBSM for all bentonite contents (Bc). By contrast, WB-PMBSM and BSM had similar <em>k</em> under low Bc conditions (10 %). However, when the Bc increased to 30 %, WB-PMBSM exhibited lower <em>k</em> than either BSM and DB-PMBSM, suggesting that different mechanisms control <em>k</em> of WB and DB-PMBSM. Conceptual models were proposed, relating the interaction mechanism and hydraulic performance of PMBSM.</div></div>","PeriodicalId":21857,"journal":{"name":"Soils and Foundations","volume":"66 1","pages":"Article 101711"},"PeriodicalIF":3.3,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145841100","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}
Pub Date : 2025-12-18DOI: 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 δhmax were about 0.10–0.55 % of the excavation depths He at the end of construction, and significant spatial and temporal effects in δh were observed. (2) The maximum ground settlement, δvmax, was generally within 0.65 % He, appearing at the distance of around 0.5 He 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.
{"title":"Observed performances and spatial effects of a set of 40 m ultra-deep rectangular excavations in Shanghai soft soils","authors":"Yinhang Zhu , Weidong Wang , Zhonghua Xu , Jinjian Chen , Zhihao Yang","doi":"10.1016/j.sandf.2025.101710","DOIUrl":"10.1016/j.sandf.2025.101710","url":null,"abstract":"<div><div>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 <em>δ</em><sub>hmax</sub> were about 0.10–0.55 % of the excavation depths <em>H</em><sub>e</sub> at the end of construction, and significant spatial and temporal effects in <em>δ</em><sub>h</sub> were observed. (2) The maximum ground settlement, <em>δ</em><sub>vmax</sub>, was generally within 0.65 % <em>H</em><sub>e</sub>, appearing at the distance of around 0.5 <em>H</em><sub>e</sub> 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.</div></div>","PeriodicalId":21857,"journal":{"name":"Soils and Foundations","volume":"66 1","pages":"Article 101710"},"PeriodicalIF":3.3,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145791659","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}
Pub Date : 2025-12-15DOI: 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 with the footing (Zone I) and exits at (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 soil, and apply to both effective and total stress analyses. The reduction factors in the classical three N-bearing capacity formula are given as =, , with , where 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.
{"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 <span><math><mrow><msup><mn>45</mn><mo>°</mo></msup><mo>+</mo><mspace></mspace><mi>φ</mi><mo>/</mo><mn>2</mn></mrow></math></span> with the footing (Zone I) and exits at <span><math><mrow><msup><mn>45</mn><mo>°</mo></msup><mo>-</mo><mspace></mspace><mi>φ</mi><mo>/</mo><mn>2</mn></mrow></math></span> (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 <span><math><mrow><mi>c</mi><mo>-</mo><mi>φ</mi></mrow></math></span> soil, and apply to both effective and total stress analyses. The reduction factors in the classical three <em>N-</em>bearing capacity formula are given as <span><math><mrow><msub><mi>ε</mi><mi>c</mi></msub><mo>=</mo><msub><mi>ε</mi><mi>q</mi></msub></mrow></math></span>=<span><math><msub><mi>ε</mi><mi>H</mi></msub></math></span>, <span><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></span>, with <span><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></span>, where <span><math><msub><mi>H</mi><mrow><mi>max</mi></mrow></msub></math></span> 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}
Pub Date : 2025-12-13DOI: 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.
{"title":"Improved analysis method for frame beams with prestressed cables in slopes based on inclined foundation stiffness","authors":"Yuan Qi , Shiguo Xiao , Tianxiang Liu","doi":"10.1016/j.sandf.2025.101712","DOIUrl":"10.1016/j.sandf.2025.101712","url":null,"abstract":"<div><div>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.</div></div>","PeriodicalId":21857,"journal":{"name":"Soils and Foundations","volume":"66 1","pages":"Article 101712"},"PeriodicalIF":3.3,"publicationDate":"2025-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145739068","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}
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.
{"title":"Large-area slope stability analysis: Performance comparison of three-dimensional limit equilibrium methods","authors":"Daichi Sugo , John Y. Choe , Saneiki Fujita , Nilo Lemuel J. Dolojan , Kenta Tozato , Reika Nomura , Kenjiro Terada , Eiji Tominaga , Shoji Iwanaga , Shuji Moriguchi","doi":"10.1016/j.sandf.2025.101703","DOIUrl":"10.1016/j.sandf.2025.101703","url":null,"abstract":"<div><div>3D limit equilibrium methods (LEMs) for assessing slope stability over large areas have been applied in some studies (e.g., <span><span>Tran et al., 2018</span></span>; 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.</div></div>","PeriodicalId":21857,"journal":{"name":"Soils and Foundations","volume":"65 6","pages":"Article 101703"},"PeriodicalIF":3.3,"publicationDate":"2025-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145525344","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}
Pub Date : 2025-11-07DOI: 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.
{"title":"Microscopic investigation into density dependence of water retention characteristics of sand during drying-wetting process","authors":"Ryunosuke Kido , Yosuke Higo , Shizuka Eshiro","doi":"10.1016/j.sandf.2025.101704","DOIUrl":"10.1016/j.sandf.2025.101704","url":null,"abstract":"<div><div>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.</div></div>","PeriodicalId":21857,"journal":{"name":"Soils and Foundations","volume":"65 6","pages":"Article 101704"},"PeriodicalIF":3.3,"publicationDate":"2025-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145474270","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}
Pub Date : 2025-11-06DOI: 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.
{"title":"Microstructural characterisation of foam-induced porosity in lightweight cemented soils using X-ray micro-tomography","authors":"F. Ferriero , L. Perrotta , L. Pappalardo , G. Buono , E. Vitale , G. Russo","doi":"10.1016/j.sandf.2025.101706","DOIUrl":"10.1016/j.sandf.2025.101706","url":null,"abstract":"<div><div>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 (<em>e.g</em>., Mercury Intrusion Porosimetry). Image analysis of X-ray microtomography scans shows that the foam-induced porosity remains stable (<em>i.e</em>., 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 (<em>i.e</em>. 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.<em>,</em> 10<sup>−10</sup> 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.</div></div>","PeriodicalId":21857,"journal":{"name":"Soils and Foundations","volume":"65 6","pages":"Article 101706"},"PeriodicalIF":3.3,"publicationDate":"2025-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145474269","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}
Pub Date : 2025-10-30DOI: 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。
{"title":"Field investigation of steel screw micropiles under axial loads in cohesionless and cohesive soils","authors":"João Batista de Oliveira Libório Dourado , Lijun Deng","doi":"10.1016/j.sandf.2025.101705","DOIUrl":"10.1016/j.sandf.2025.101705","url":null,"abstract":"<div><div>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<sup>−1</sup>. 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.</div></div>","PeriodicalId":21857,"journal":{"name":"Soils and Foundations","volume":"65 6","pages":"Article 101705"},"PeriodicalIF":3.3,"publicationDate":"2025-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145417144","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}
The reuse of excavated soil is a popular topic all around the world. To decrease the contaminants in excavated soil influencing the ground, an attenuation layer is generally used to absorb these contaminants and isolate the excavated soil and ground. The drainage clogging problem that is sometimes generated has attracted much attention in embankment engineering. The attenuation layer drainage effect is not only related to the loading capacity of the ground, but also to the soil properties. Thus, it is significant to clarify the mechanism of drainage clogging. As the micro monitoring of clogging is still difficult to achieve, a numerical simulation method is used in the present study to elaborate this mechanism. Based on the coupled lattice Boltzmann method (LBM) and discrete element method (DEM), the drainage clogging phenomenon during the filtering process is simulated from a micro perspective. The results indicate that particles can form an arch structure and lead to clogging above the pore of the attenuation layer. The formation of such a clogging arch structure prevents the discharge of soil particles and greatly decreases the fluid velocity, approximately 2.7 and 9.3 times for the two types of soil used in this study, namely, Soil A and Soil B, respectively. It is noted that the fluid velocity, rather than impermeability, remains a basic value. The velocity distribution around the pore of the attenuation layer has a certain shape depending on the velocity of the LBM cells. The size of this distribution regularly changes with the distance to the attenuation layer pore. In addition, knowledge of the soil skeleton is necessary for analyzing the arch-forming process in polydisperse particle systems. The larger particles (0.043–0.085 cm) are closely related to the formation of the soil skeleton, whereas the finer particles are related to the filling and stabilization of the soil skeleton. The clog stabilization of the soil particles in these two samples is mainly controlled by the average normal forces (1.87 × 10−6 N and 1.20 × 10−6 N, respectively) according to the variation in forces during the clogging process. Based on the analysis, an explanation of the clogging process is proposed in this study from a microscopic perspective, providing a better description of the soil skeleton clogging theory under embankment drainage.
{"title":"Interface clogging between soil and attenuation layer of embankment based on LBM-DEM coupled numerical method","authors":"Xudong Zhang, Atsushi Takai, Tomohiro Kato, Takeshi Katsumi","doi":"10.1016/j.sandf.2025.101697","DOIUrl":"10.1016/j.sandf.2025.101697","url":null,"abstract":"<div><div>The reuse of excavated soil is a popular topic all around the world. To decrease the contaminants in excavated soil influencing the ground, an attenuation layer is generally used to absorb these contaminants and isolate the excavated soil and ground. The drainage clogging problem that is sometimes generated has attracted much attention in embankment engineering. The attenuation layer drainage effect is not only related to the loading capacity of the ground, but also to the soil properties. Thus, it is significant to clarify the mechanism of drainage clogging. As the micro monitoring of clogging is still difficult to achieve, a numerical simulation method is used in the present study to elaborate this mechanism. Based on the coupled lattice Boltzmann method (LBM) and discrete element method (DEM), the drainage clogging phenomenon during the filtering process is simulated from a micro perspective. The results indicate that particles can form an arch structure and lead to clogging above the pore of the attenuation layer. The formation of such a clogging arch structure prevents the discharge of soil particles and greatly decreases the fluid velocity, approximately 2.7 and 9.3 times for the two types of soil used in this study, namely, Soil A and Soil B, respectively. It is noted that the fluid velocity, rather than impermeability, remains a basic value. The velocity distribution around the pore of the attenuation layer has a certain shape depending on the velocity of the LBM cells. The size of this distribution regularly changes with the distance to the attenuation layer pore. In addition, knowledge of the soil skeleton is necessary for analyzing the arch-forming process in polydisperse particle systems. The larger particles (0.043–0.085 cm) are closely related to the formation of the soil skeleton, whereas the finer particles are related to the filling and stabilization of the soil skeleton. The clog stabilization of the soil particles in these two samples is mainly controlled by the average normal forces (1.87 × 10<sup>−6</sup> N and 1.20 × 10<sup>−6</sup> N, respectively) according to the variation in forces during the clogging process. Based on the analysis, an explanation of the clogging process is proposed in this study from a microscopic perspective, providing a better description of the soil skeleton clogging theory under embankment drainage.</div></div>","PeriodicalId":21857,"journal":{"name":"Soils and Foundations","volume":"65 6","pages":"Article 101697"},"PeriodicalIF":3.3,"publicationDate":"2025-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145325923","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}
Pub Date : 2025-10-10DOI: 10.1016/j.sandf.2025.101655
Yinglong Liu , Maliki Otieboame Djandjieme , Kimitoshi Hayano , Hiromoto Yamauchi , Cong Li
Sandy soils used in backfilling to support daily traffic and pavement loads are prone to liquefaction during earthquakes, causing extensive damage to underground infrastructures, disrupting daily life, and requiring costly repairs. Although stabilizers, such as cement-based treatments, have been widely used to address liquefaction, concerns regarding their environmental effects, particularly carbon emissions during cement production, necessitate the investigation into more sustainable materials. Compared with traditional cement-based materials, paper sludge ash-based stabilizer (PSAS) processing emits significantly lower amounts of carbon dioxide. Furthermore, PSA is produced as a by-product of paperboard and roll paper manufacturing, and wood is a renewable resource, while cement is made from limestone, a nonrenewable natural resource. In this study, PSAS-treated backfill sand was synthesized to assess its strength, liquefaction resistance, and durability. The PSAS-treated sand maintained a compressive strength of approximately 500 kPa at an addition ratio of 5.0 %, ensuring moderate strength for excavations near manholes and pipes. Consolidated drained triaxial compression tests showed that the cohesion (cd) increased significantly with extended curing periods, increased density, and higher additive contents. Conversely, the angle of shear resistance (ϕd) remained largely unchanged with variations in density and curing periods, but increased as the additive content was increased. In addition, the treated sand demonstrated non-liquefaction behavior with increased deformation resistance over time. During dry–wet curing cycles, the compressive strength of the PSAS-treated sand initially increased, but then decreased as the number of cycles increased. However, the cone resistance of treated sand remained significantly higher than that of untreated sand, indicating high durability under restrained conditions. Thus, PSAS-treated sand was seen to meet the desired mechanical and structural requirements, while adhering to environmental sustainability goals, demonstrating significant potential as a backfill material in areas with seismic activity.
{"title":"Normal and seismic performance of backfill sand enhanced with biomass waste-derived materials under road pavement","authors":"Yinglong Liu , Maliki Otieboame Djandjieme , Kimitoshi Hayano , Hiromoto Yamauchi , Cong Li","doi":"10.1016/j.sandf.2025.101655","DOIUrl":"10.1016/j.sandf.2025.101655","url":null,"abstract":"<div><div>Sandy soils used in backfilling to support daily traffic and pavement loads are prone to liquefaction during earthquakes, causing extensive damage to underground infrastructures, disrupting daily life, and requiring costly repairs. Although stabilizers, such as cement-based treatments, have been widely used to address liquefaction, concerns regarding their environmental effects, particularly carbon emissions during cement production, necessitate the investigation into more sustainable materials. Compared with traditional cement-based materials, paper sludge ash-based stabilizer (PSAS) processing emits significantly lower amounts of carbon dioxide. Furthermore, PSA is produced as a by-product of paperboard and roll paper manufacturing, and wood is a renewable resource, while cement is made from limestone, a nonrenewable natural resource. In this study, PSAS-treated backfill sand was synthesized to assess its strength, liquefaction resistance, and durability. The PSAS-treated sand maintained a compressive strength of approximately 500 kPa at an addition ratio of 5.0 %, ensuring moderate strength for excavations near manholes and pipes. Consolidated drained triaxial compression tests showed that the cohesion (<em>c<sub>d</sub></em>) increased significantly with extended curing periods, increased density, and higher additive contents. Conversely, the angle of shear resistance (<em>ϕ</em><sub>d</sub>) remained largely unchanged with variations in density and curing periods, but increased as the additive content was increased. In addition, the treated sand demonstrated non-liquefaction behavior with increased deformation resistance over time. During dry–wet curing cycles, the compressive strength of the PSAS-treated sand initially increased, but then decreased as the number of cycles increased. However, the cone resistance of treated sand remained significantly higher than that of untreated sand, indicating high durability under restrained conditions. Thus, PSAS-treated sand was seen to meet the desired mechanical and structural requirements, while adhering to environmental sustainability goals, demonstrating significant potential as a backfill material in areas with seismic activity.</div></div>","PeriodicalId":21857,"journal":{"name":"Soils and Foundations","volume":"65 6","pages":"Article 101655"},"PeriodicalIF":3.3,"publicationDate":"2025-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145269633","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}
扫码关注我们
求助内容：
应助结果提醒方式：
京公网安备 11010802042870号