Bin Zhu, Simin Yuan, Lujun Wang, Yanjing Liu, Yunmin Chen
To safely and effectively explore the natural methane hydrate, it is crucial to examine the mechanical behavior of methane hydrate‐bearing sediments (MHBSs). Natural methane hydrate unevenly distributes in pores or bonds with soil particles in MHBS, changing the mechanical behavior of MHBS including stiffness, shear strength, and dilatancy. This paper presents an anisotropic critical state model for MHBS considering hydrate pore‐filling and cementing effects. Based on the unified critical state model for both clay and sand, an equivalent hydrate ratio is defined to address pore‐filling effect. Cohesive strength and its hardening law are introduced to characterize hydrate cementation. To describe the anisotropic behavior, the inherent anisotropy of soil particles and hydrates are modeled separately, and rotation hardening is introduced to describe the stress‐induced anisotropy. Comparisons with existing triaxial tests of both synthetic and natural MHBS demonstrate that the proposed model comprehensively describes the mechanical behavior of MHBS. Detailed predictions indicate that hydrate pore‐filling affects the hydrate‐dependent stiffness and dilatancy of MHBS, which become more pronounced with increasing hydrate saturation. Cementing effect increases the initial stiffness and peak strength of MHBS. The pronounced influence of inherent anisotropic parameters on pre‐peak stress–strain relation of MHBS is noted, and increasing hydrate saturation enhances the effect of hydrate anisotropy. These predictions contribute to a better understanding of the relation between hydrate morphologies and MHBS mechanical properties.
{"title":"A Critical State Constitutive Model for Methane Hydrate‐Bearing Sediments Considering Hydrate Pore‐Filling and Cementing Effects","authors":"Bin Zhu, Simin Yuan, Lujun Wang, Yanjing Liu, Yunmin Chen","doi":"10.1002/nag.3873","DOIUrl":"https://doi.org/10.1002/nag.3873","url":null,"abstract":"To safely and effectively explore the natural methane hydrate, it is crucial to examine the mechanical behavior of methane hydrate‐bearing sediments (MHBSs). Natural methane hydrate unevenly distributes in pores or bonds with soil particles in MHBS, changing the mechanical behavior of MHBS including stiffness, shear strength, and dilatancy. This paper presents an anisotropic critical state model for MHBS considering hydrate pore‐filling and cementing effects. Based on the unified critical state model for both clay and sand, an equivalent hydrate ratio is defined to address pore‐filling effect. Cohesive strength and its hardening law are introduced to characterize hydrate cementation. To describe the anisotropic behavior, the inherent anisotropy of soil particles and hydrates are modeled separately, and rotation hardening is introduced to describe the stress‐induced anisotropy. Comparisons with existing triaxial tests of both synthetic and natural MHBS demonstrate that the proposed model comprehensively describes the mechanical behavior of MHBS. Detailed predictions indicate that hydrate pore‐filling affects the hydrate‐dependent stiffness and dilatancy of MHBS, which become more pronounced with increasing hydrate saturation. Cementing effect increases the initial stiffness and peak strength of MHBS. The pronounced influence of inherent anisotropic parameters on pre‐peak stress–strain relation of MHBS is noted, and increasing hydrate saturation enhances the effect of hydrate anisotropy. These predictions contribute to a better understanding of the relation between hydrate morphologies and MHBS mechanical properties.","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":null,"pages":null},"PeriodicalIF":4.0,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142449553","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}
Shabnam Shirazizadeh, Amin Keshavarz, Majid Beygi, Mohammad Saberian, Jie Li, Ramin Vali
Although considerable research has explored the static and seismic bearing capacity of strip footings on slopes or excavations, the influence of clay strength anisotropy on the bearing capacity of strip footing near excavations, specifically considering pseudo‐dynamic conditions, remains unexplored. This study used the finite element limit analysis (FELA) method to evaluate the impact of clay strength anisotropy on the seismic bearing capacity of strip footings. The effects of various dimensionless parameters on the bearing capacity were examined, which include shear wavelength, the setback distance ratio, vertical height ratio, soil strength ratio, soil strength heterogeneity, anisotropic ratio, and horizontal and vertical acceleration coefficients. Design charts were developed to compute the seismic bearing capacity of strip footings on nonhomogeneous and anisotropic excavations under pseudo‐static conditions. Furthermore, the effects of vertical acceleration coefficients and shear wavelength on the seismic bearing capacity of strip footing near excavation in nonhomogeneous and anisotropic soils were investigated.
{"title":"Seismic Bearing Capacity of Strip Footing on Excavations Considering Soil Strength Anisotropy Using Modified Pseudo‐Dynamic and Pseudo‐Static Approaches","authors":"Shabnam Shirazizadeh, Amin Keshavarz, Majid Beygi, Mohammad Saberian, Jie Li, Ramin Vali","doi":"10.1002/nag.3864","DOIUrl":"https://doi.org/10.1002/nag.3864","url":null,"abstract":"Although considerable research has explored the static and seismic bearing capacity of strip footings on slopes or excavations, the influence of clay strength anisotropy on the bearing capacity of strip footing near excavations, specifically considering pseudo‐dynamic conditions, remains unexplored. This study used the finite element limit analysis (FELA) method to evaluate the impact of clay strength anisotropy on the seismic bearing capacity of strip footings. The effects of various dimensionless parameters on the bearing capacity were examined, which include shear wavelength, the setback distance ratio, vertical height ratio, soil strength ratio, soil strength heterogeneity, anisotropic ratio, and horizontal and vertical acceleration coefficients. Design charts were developed to compute the seismic bearing capacity of strip footings on nonhomogeneous and anisotropic excavations under pseudo‐static conditions. Furthermore, the effects of vertical acceleration coefficients and shear wavelength on the seismic bearing capacity of strip footing near excavation in nonhomogeneous and anisotropic soils were investigated.","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":null,"pages":null},"PeriodicalIF":4.0,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142449552","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}
Zhang Mingli, Liu Yuefeng, Wang Fei, Wen Zhi, Zhang Ruiling, Hao Dongmiao, Feng Wei, Yan Xinchen
Under the influence of large temperature differences in an impermeable pavement layer of wide embankment in permafrost regions, liquid water accumulates at the bottom of the impermeable cover. The phenomenon is known as the pot‐cover effect and leads to an increase in soil water content and a reduction in bearing capacity of wide embankments. At present, water vapor and liquid water migrations and their effect on embankment thermal‐moisture stability have not been fully confirmed. To better understand the moisture transport and accumulation process within embankments, hydrothermal field monitoring was conducted from 2009 to 2011 on an asphalt concrete layer highway in Beiluhe, central Tibet Plateau. The field monitoring results show that soil moisture content between 50 and 250 cm below the pavement continuously increases with the number of freeze‐thaw cycles, with the largest increase during the 2 years being 6.4%. Then, a coupled hydro‐vapor‐thermal transport model was established and verified. Furthermore, the model was used to analyze the numerical recurrence of the pot‐cover effect. The simulation indicates that the upward migration of liquid water during the freezing period is less than the downward migration during the thawing period, while vapor migrates downward during the thawing period but upward during the freezing period. The migration of water vapor within the embankment during the freezing period is the main cause of the pot‐cover effect in permafrost regions. In addition, the research results can provide new ideas for understanding the internal mechanism of thermal‐moisture dynamics of the embankment and the stability prediction of permafrost engineering.
{"title":"Pot‐Cover Effect in Permafrost Embankment: In Situ Experiment Evidence and Mechanism Simulation","authors":"Zhang Mingli, Liu Yuefeng, Wang Fei, Wen Zhi, Zhang Ruiling, Hao Dongmiao, Feng Wei, Yan Xinchen","doi":"10.1002/nag.3867","DOIUrl":"https://doi.org/10.1002/nag.3867","url":null,"abstract":"Under the influence of large temperature differences in an impermeable pavement layer of wide embankment in permafrost regions, liquid water accumulates at the bottom of the impermeable cover. The phenomenon is known as the pot‐cover effect and leads to an increase in soil water content and a reduction in bearing capacity of wide embankments. At present, water vapor and liquid water migrations and their effect on embankment thermal‐moisture stability have not been fully confirmed. To better understand the moisture transport and accumulation process within embankments, hydrothermal field monitoring was conducted from 2009 to 2011 on an asphalt concrete layer highway in Beiluhe, central Tibet Plateau. The field monitoring results show that soil moisture content between 50 and 250 cm below the pavement continuously increases with the number of freeze‐thaw cycles, with the largest increase during the 2 years being 6.4%. Then, a coupled hydro‐vapor‐thermal transport model was established and verified. Furthermore, the model was used to analyze the numerical recurrence of the pot‐cover effect. The simulation indicates that the upward migration of liquid water during the freezing period is less than the downward migration during the thawing period, while vapor migrates downward during the thawing period but upward during the freezing period. The migration of water vapor within the embankment during the freezing period is the main cause of the pot‐cover effect in permafrost regions. In addition, the research results can provide new ideas for understanding the internal mechanism of thermal‐moisture dynamics of the embankment and the stability prediction of permafrost engineering.","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":null,"pages":null},"PeriodicalIF":4.0,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142449577","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}
Nazanin Irani, Luis Felipe Prada‐Sarmiento, Merita Tafili, Mohammad Salimi, Torsten Wichtmann, Theodoros Triantafyllidis
The advantages of constitutive models in energy‐conservation frameworks have been widely addressed in the literature. A key component is choosing an appropriate energy potential to derive the hyperelastic constitutive equations. This article investigates the advantages and limitations of different energy potentials found in the literature based on mathematical conditions to guarantee numerical stability, such as the desired order of homogeneity, positive and non‐singular stiffness within the application range, and equivalent Poisson's ratio from a constitutive modelling standpoint. Potentials meeting the aforementioned criteria are employed to simulate the response envelopes of Karlsruhe fine sand (KFS). Moreover, the performance of the potentials, in conjunction with plasticity theories, is examined. To achieve this, the hyperelastic constitutive equations have been coupled with the bounding surface plasticity model of Dafalias and Manzari to reproduce the soil response in a hyperelastic–plastic frame. Finally, one of the potentials is modified, whereas recommendations for incorporating other appropriate free energy functions into different soil constitutive models are presented. Furthermore, 100 closed elastic strain cycles have been simulated with the bounding surface plasticity model of Dafalias and Manzari considering the original hypoelastic stiffness and hyperelastic–plastic constitutive equations. Using the hypoelastic framework in the simulation led to stress accumulation after 100 closed elastic strain loops, while a reversible response was predicted using the hyperelastic stiffness tensor.
{"title":"Assessment of Free Energy Functions for Sand","authors":"Nazanin Irani, Luis Felipe Prada‐Sarmiento, Merita Tafili, Mohammad Salimi, Torsten Wichtmann, Theodoros Triantafyllidis","doi":"10.1002/nag.3852","DOIUrl":"https://doi.org/10.1002/nag.3852","url":null,"abstract":"The advantages of constitutive models in energy‐conservation frameworks have been widely addressed in the literature. A key component is choosing an appropriate energy potential to derive the hyperelastic constitutive equations. This article investigates the advantages and limitations of different energy potentials found in the literature based on mathematical conditions to guarantee numerical stability, such as the desired order of homogeneity, positive and non‐singular stiffness within the application range, and equivalent Poisson's ratio from a constitutive modelling standpoint. Potentials meeting the aforementioned criteria are employed to simulate the response envelopes of Karlsruhe fine sand (KFS). Moreover, the performance of the potentials, in conjunction with plasticity theories, is examined. To achieve this, the hyperelastic constitutive equations have been coupled with the bounding surface plasticity model of Dafalias and Manzari to reproduce the soil response in a hyperelastic–plastic frame. Finally, one of the potentials is modified, whereas recommendations for incorporating other appropriate free energy functions into different soil constitutive models are presented. Furthermore, 100 closed elastic strain cycles have been simulated with the bounding surface plasticity model of Dafalias and Manzari considering the original hypoelastic stiffness and hyperelastic–plastic constitutive equations. Using the hypoelastic framework in the simulation led to stress accumulation after 100 closed elastic strain loops, while a reversible response was predicted using the hyperelastic stiffness tensor.","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":null,"pages":null},"PeriodicalIF":4.0,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142440031","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}
Pierre Guy Atangana Njock, Zhen‐Yu Yin, Ning Zhang
Contemporary geoengineering challenges grapple with the plateauing of both existing algorithms and their depth of insights, a phenomenon exacerbated by the scarcity of high‐fidelity data. Although existing solutions such as Monte‐Carlo method can generate abundant data, they are not sufficiently robust for ensuring the high fidelity of data. This study proposes a novel data augmentation framework that combines statistical and machine learning methods to generate high‐fidelity synthetic data, which closely align with field data in terms of the statistical and empirical attributes. The innovations of the proposed approach lie in the integration of Copulas theory for data generation, a developed geo‐regression anomaly detection (GRAD) for adjusting data attributes, and an evolutionary polynomial regression for data consistency enforcement. The multilayer perceptron (MLP) and a wide‐and‐deep (WaD) networks are applied to assess the effectiveness of high‐fidelity data augmentation using jet grouting data. The outcomes reveal the robustness of the synthetic data generation framework, achieving satisfactory fidelity in both empirical and statistical attributes. The proposed data augmentation improved the R2 and MAE achieved by MLP and WaD up to 28.37% under data fractions ranging from 0.2 to 1. MLP and WaD yielded comparable results in terms of accuracy and generalization ability across various augmented fractions. This indicates that the accuracy of synthetic data plays a pivotal role, suggesting improving data quality can be highly effective in boosting performance, regardless of the model complexity. This study contributes valuable insights to addressing the challenges of scare high‐fidelity data in geoengineering.
{"title":"High‐Fidelity Data Augmentation for Few‐Shot Learning in Jet Grout Injection Applications","authors":"Pierre Guy Atangana Njock, Zhen‐Yu Yin, Ning Zhang","doi":"10.1002/nag.3862","DOIUrl":"https://doi.org/10.1002/nag.3862","url":null,"abstract":"Contemporary geoengineering challenges grapple with the plateauing of both existing algorithms and their depth of insights, a phenomenon exacerbated by the scarcity of high‐fidelity data. Although existing solutions such as Monte‐Carlo method can generate abundant data, they are not sufficiently robust for ensuring the high fidelity of data. This study proposes a novel data augmentation framework that combines statistical and machine learning methods to generate high‐fidelity synthetic data, which closely align with field data in terms of the statistical and empirical attributes. The innovations of the proposed approach lie in the integration of Copulas theory for data generation, a developed geo‐regression anomaly detection (GRAD) for adjusting data attributes, and an evolutionary polynomial regression for data consistency enforcement. The multilayer perceptron (MLP) and a wide‐and‐deep (WaD) networks are applied to assess the effectiveness of high‐fidelity data augmentation using jet grouting data. The outcomes reveal the robustness of the synthetic data generation framework, achieving satisfactory fidelity in both empirical and statistical attributes. The proposed data augmentation improved the <jats:italic>R<jats:sup>2</jats:sup></jats:italic> and MAE achieved by MLP and WaD up to 28.37% under data fractions ranging from 0.2 to 1. MLP and WaD yielded comparable results in terms of accuracy and generalization ability across various augmented fractions. This indicates that the accuracy of synthetic data plays a pivotal role, suggesting improving data quality can be highly effective in boosting performance, regardless of the model complexity. This study contributes valuable insights to addressing the challenges of scare high‐fidelity data in geoengineering.","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":null,"pages":null},"PeriodicalIF":4.0,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142405482","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}
Tong Zhang, Jian Ji, Shigui Du, Jian Song, Wengui Huang
The permanent displacement of earth slopes during earthquake shaking is a key indicator for landslide hazard assessment. Previous studies mostly attempt to evaluate the earthquake‐induced displacement of dry or saturated soil slopes, while it is less common to deal with partially saturated soils. In the present study, a simplified procedure is proposed to account for the seismic‐induced excess pore pressure in slopes with partially saturated sandy soils. The effect of matric suction, suction stress, and excess pore pressure on the yield acceleration of partially saturated sandy slopes is investigated, and the coupled Newmark sliding block method, known as the flexible soil columns with dynamic shear modulus and damping ratio, is modified to estimate the seismic slope displacement. Detailed discussions are made about the effect of different degrees of saturation on the excess pore pressure ratio, yield acceleration, and slope displacement. The numerical results show that the excess pore pressure ratio tends to exponentially increase with saturation, and the change of yield acceleration and displacement with saturation can be divided into suction stress dominant and excess pore water pressure dominant stages.
{"title":"Effect of Excess Pore Pressure on Earthquake‐Induced Displacement of Partially Saturated Sandy Soil Slopes: Flexible Sliding Block Analysis","authors":"Tong Zhang, Jian Ji, Shigui Du, Jian Song, Wengui Huang","doi":"10.1002/nag.3855","DOIUrl":"https://doi.org/10.1002/nag.3855","url":null,"abstract":"The permanent displacement of earth slopes during earthquake shaking is a key indicator for landslide hazard assessment. Previous studies mostly attempt to evaluate the earthquake‐induced displacement of dry or saturated soil slopes, while it is less common to deal with partially saturated soils. In the present study, a simplified procedure is proposed to account for the seismic‐induced excess pore pressure in slopes with partially saturated sandy soils. The effect of matric suction, suction stress, and excess pore pressure on the yield acceleration of partially saturated sandy slopes is investigated, and the coupled Newmark sliding block method, known as the flexible soil columns with dynamic shear modulus and damping ratio, is modified to estimate the seismic slope displacement. Detailed discussions are made about the effect of different degrees of saturation on the excess pore pressure ratio, yield acceleration, and slope displacement. The numerical results show that the excess pore pressure ratio tends to exponentially increase with saturation, and the change of yield acceleration and displacement with saturation can be divided into suction stress dominant and excess pore water pressure dominant stages.","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":null,"pages":null},"PeriodicalIF":4.0,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142405483","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 limit equilibrium method has been widely used in the study of searching the slip surface of slopes. However, the method ignores the deformation characteristics of the rock mass and assumes that the shape of the slip surface is circular, which is quite different from the actual situation of the slope. For this reason, this paper proposes a fast search method for noncircular slip surface considering the deformation characteristics of the rock mass. The method is able to calculate the compression and shear deformation energies stored in the slip surface, as well as the virtual displacement generated by the slide mass when the slope is in a critical equilibrium state. The direction of motion of the slide mass is further calculated from the magnitude of the virtual displacement. In addition, this paper improves the generation of new solutions in the simulated annealing (SA) algorithm for the structural characteristics of the slip surface of the slope, thus achieving a fast search of the slip surface. Finally, the method of this paper is compared with the test question of ACADS and the simulation results of the finite difference method (FDM) to verify the effectiveness of the method of this paper.
{"title":"Noncircular Slip Surface Search on Slopes Based on Minimum Potential Energy Method and Improved SA Algorithm","authors":"Yi Tang, Hang Lin","doi":"10.1002/nag.3865","DOIUrl":"https://doi.org/10.1002/nag.3865","url":null,"abstract":"The limit equilibrium method has been widely used in the study of searching the slip surface of slopes. However, the method ignores the deformation characteristics of the rock mass and assumes that the shape of the slip surface is circular, which is quite different from the actual situation of the slope. For this reason, this paper proposes a fast search method for noncircular slip surface considering the deformation characteristics of the rock mass. The method is able to calculate the compression and shear deformation energies stored in the slip surface, as well as the virtual displacement generated by the slide mass when the slope is in a critical equilibrium state. The direction of motion of the slide mass is further calculated from the magnitude of the virtual displacement. In addition, this paper improves the generation of new solutions in the simulated annealing (SA) algorithm for the structural characteristics of the slip surface of the slope, thus achieving a fast search of the slip surface. Finally, the method of this paper is compared with the test question of ACADS and the simulation results of the finite difference method (FDM) to verify the effectiveness of the method of this paper.","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":null,"pages":null},"PeriodicalIF":4.0,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142397721","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}
Most constitutive models did not initially consider special behaviors in some soils with singular characteristics (e.g., soft soils with diatom content). For example, at first, these models did not consider the effect of soil structure and viscosity. However, in the last decades, these variables have been incorporated into several constitutive models to describe the mechanical behavior of the soil in its natural state. Structure and viscosity laws that adequately reproduce the soil behavior had to be developed to include these variables. This paper compares the mechanical behavior of soft soils in Bogotá with different constitutive models. Bogotá’s soft soils are lacustrine deposits with a high content of diatoms in their structure. Natural soil samples with intact structures show a high‐water content, which can be higher than 300%, liquid limits of up to 400%, void ratios higher than five, and friction angles of almost 40°. In addition, the model validations were made through the simulations of triaxial tests in compression and shear paths. Modified Cam Clay (MCC), hypoplastic (HP), and subloading Cam Clay (SCC) were the constitutive models used. Two models are based on an elastoplastic framework, and the third uses a HP framework. Several lessons were learned from the simulations regarding the strengths and weaknesses of the models compared to the tests carried out. Finally, the extensive discussion revolves around determining the most suitable model for simulating the mechanical behavior of soft soils containing diatoms in Bogotá.
大多数结构模型最初都没有考虑某些具有特殊性质的土壤（如硅藻含量高的软土）的特殊行为。例如，这些模型最初没有考虑土壤结构和粘度的影响。然而，在过去的几十年中，这些变量已被纳入多个构成模型，以描述自然状态下土壤的力学行为。必须开发能充分再现土壤行为的结构和粘度定律，以纳入这些变量。本文比较了波哥大软土在不同构成模型下的力学行为。波哥大的软土是湖相沉积物，其结构中含有大量硅藻。结构完整的天然土壤样本含水量很高，可高于 300%，液限高达 400%，空隙率高于 5，摩擦角接近 40°。此外，还通过模拟压缩和剪切路径下的三轴试验对模型进行了验证。所使用的构成模型包括改良凸轮粘土（MCC）、低塑性凸轮粘土（HP）和超载凸轮粘土（SCC）。其中两个模型基于弹塑性框架，第三个模型使用 HP 框架。与已进行的测试相比，从模拟中吸取了有关模型优缺点的若干经验教训。最后，围绕确定最适合模拟波哥大含硅藻软土力学行为的模型进行了广泛讨论。
{"title":"Use of Advanced Constitutive Models for the Mechanical Behavior of Soft Soils With Diatoms From Bogotá (Colombia)","authors":"Cristhian Mendoza, Márcio Muniz de Farias","doi":"10.1002/nag.3863","DOIUrl":"https://doi.org/10.1002/nag.3863","url":null,"abstract":"Most constitutive models did not initially consider special behaviors in some soils with singular characteristics (e.g., soft soils with diatom content). For example, at first, these models did not consider the effect of soil structure and viscosity. However, in the last decades, these variables have been incorporated into several constitutive models to describe the mechanical behavior of the soil in its natural state. Structure and viscosity laws that adequately reproduce the soil behavior had to be developed to include these variables. This paper compares the mechanical behavior of soft soils in Bogotá with different constitutive models. Bogotá’s soft soils are lacustrine deposits with a high content of diatoms in their structure. Natural soil samples with intact structures show a high‐water content, which can be higher than 300%, liquid limits of up to 400%, void ratios higher than five, and friction angles of almost 40°. In addition, the model validations were made through the simulations of triaxial tests in compression and shear paths. Modified Cam Clay (MCC), hypoplastic (HP), and subloading Cam Clay (SCC) were the constitutive models used. Two models are based on an elastoplastic framework, and the third uses a HP framework. Several lessons were learned from the simulations regarding the strengths and weaknesses of the models compared to the tests carried out. Finally, the extensive discussion revolves around determining the most suitable model for simulating the mechanical behavior of soft soils containing diatoms in Bogotá.","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":null,"pages":null},"PeriodicalIF":4.0,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142397744","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}
Cohesive material columns have been extensively used in foundation improvement projects to enhance the bearing capacity of composite foundations and mitigate post‐construction settlement. However, the low permeability of cohesive material columns restricts the dissipation of pore water primarily through the top surface of the foundation, potentially resulting in longer drainage paths compared to foundations treated with granular material columns or vertical drains. Moreover, the impact of non‐Darcian flow within soils on consolidation behavior becomes increasingly pronounced as the drainage path increases. Consequently, a novel analytical model for the consolidation of impervious column‐assisted foundations is established, which can incorporate the seepage model accounting for the initial hydraulic gradient. The accuracy and reasonableness of the obtained solution are then validated by conducting a comparative analysis with existing models and through a detailed case study. Furthermore, a parametric analysis is conducted to delve into the influence of several crucial factors on the consolidation performance. The findings demonstrate that non‐Darcian flow has a greater influence on composite foundations compared to natural foundations. Additionally, the threshold value of the well‐diameter ratio decreases with the increase in the initial hydraulic gradient. Finally, the final seepage front remains at a shallower position when the column–soil modulus ratio becomes larger, and the influence of non‐Darcian flow on the consolidation rate becomes more pronounced.
{"title":"Analytical Solutions for Consolidation of Soft Ground With Impervious Columns Considering Non‐Darcian Flow","authors":"Kuo Li, Mengmeng Lu, Jinxin Sun","doi":"10.1002/nag.3857","DOIUrl":"https://doi.org/10.1002/nag.3857","url":null,"abstract":"Cohesive material columns have been extensively used in foundation improvement projects to enhance the bearing capacity of composite foundations and mitigate post‐construction settlement. However, the low permeability of cohesive material columns restricts the dissipation of pore water primarily through the top surface of the foundation, potentially resulting in longer drainage paths compared to foundations treated with granular material columns or vertical drains. Moreover, the impact of non‐Darcian flow within soils on consolidation behavior becomes increasingly pronounced as the drainage path increases. Consequently, a novel analytical model for the consolidation of impervious column‐assisted foundations is established, which can incorporate the seepage model accounting for the initial hydraulic gradient. The accuracy and reasonableness of the obtained solution are then validated by conducting a comparative analysis with existing models and through a detailed case study. Furthermore, a parametric analysis is conducted to delve into the influence of several crucial factors on the consolidation performance. The findings demonstrate that non‐Darcian flow has a greater influence on composite foundations compared to natural foundations. Additionally, the threshold value of the well‐diameter ratio decreases with the increase in the initial hydraulic gradient. Finally, the final seepage front remains at a shallower position when the column–soil modulus ratio becomes larger, and the influence of non‐Darcian flow on the consolidation rate becomes more pronounced.","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":null,"pages":null},"PeriodicalIF":4.0,"publicationDate":"2024-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142385428","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}
Liang Li, Man Wang, Hongyun Jiao, Xiuli Du, Peixin Shi
A semi‐analytical method for the near‐field antiplane wave propagation analysis in the layered fluid‐saturated porous media (FSPM) is proposed based on the Biot u–U dynamic formulation. The wave propagation equations of the FSPM are decoupled by the variable‐separating method. The thin‐layer element method (TLEM) is applied to discretize the infinite domain and construct the consistent artificial boundary condition. The finite element method (FEM) is adopted for the space discretization of the finite domain and the numerical solution of the dynamic response. The proposed method is validated by the comparison of the numerical results of this method with those in the published references and acquired from the remote artificial boundary. Subsequently, this method is applied to investigate typical near‐field antiplane wave propagation problems in the FSPM. Parametric sensitivity investigations are also executed to explore the impact of mechanical parameters, including permeability coefficients, porosity, and shear modulus of the solid phase, on the dynamic response of the FSPM. The study results confirm the efficacy and efficiency of the proposed method in the near‐field antiplane wave propagation analysis in the FSPM.
{"title":"A Semi‐Analytical Method for Simulating Near‐Field Antiplane Wave Propagation in Layered Fluid‐Saturated Porous Media","authors":"Liang Li, Man Wang, Hongyun Jiao, Xiuli Du, Peixin Shi","doi":"10.1002/nag.3859","DOIUrl":"https://doi.org/10.1002/nag.3859","url":null,"abstract":"A semi‐analytical method for the near‐field antiplane wave propagation analysis in the layered fluid‐saturated porous media (FSPM) is proposed based on the Biot <jats:italic>u</jats:italic>–<jats:italic>U</jats:italic> dynamic formulation. The wave propagation equations of the FSPM are decoupled by the variable‐separating method. The thin‐layer element method (TLEM) is applied to discretize the infinite domain and construct the consistent artificial boundary condition. The finite element method (FEM) is adopted for the space discretization of the finite domain and the numerical solution of the dynamic response. The proposed method is validated by the comparison of the numerical results of this method with those in the published references and acquired from the remote artificial boundary. Subsequently, this method is applied to investigate typical near‐field antiplane wave propagation problems in the FSPM. Parametric sensitivity investigations are also executed to explore the impact of mechanical parameters, including permeability coefficients, porosity, and shear modulus of the solid phase, on the dynamic response of the FSPM. The study results confirm the efficacy and efficiency of the proposed method in the near‐field antiplane wave propagation analysis in the FSPM.","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":null,"pages":null},"PeriodicalIF":4.0,"publicationDate":"2024-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142385626","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}
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