This paper introduces a novel approach that combines proper orthogonal decomposition (POD) with thermodynamics‐based artificial neural networks (TANNs) to capture the macroscopic behavior of complex inelastic systems and derive macro‐elements in geomechanics. The methodology leverages POD to extract macroscopic internal state variables from microscopic state information, thereby enriching the macroscopic state description used to train an energy potential network within the TANN framework. The thermodynamic consistency provided by TANN, combined with the hierarchical nature of POD, allows to reproduce complex, nonlinear inelastic material behaviors, as well as macroscopic geomechanical systems responses. The approach is validated through applications of increasing complexity, demonstrating its capability to reproduce high‐fidelity simulation data. The applications proposed include the homogenization of continuous inelastic representative unit cells and the derivation of a macro‐element for a geotechnical system involving a monopile in a clay layer subjected to horizontal loading. Eventually, the projection operators directly obtained via POD are exploited to easily reconstruct the microscopic fields. The results indicate that the POD‐TANN approach not only offers accuracy in reproducing the studied constitutive responses, but also reduces computational costs, making it a practical tool for the multiscale modeling of heterogeneous inelastic geomechanical systems.
本文介绍了一种将适当正交分解（POD）与基于热力学的人工神经网络（TANNs）相结合的新方法，以捕捉复杂非弹性系统的宏观行为，并推导出地质力学中的宏观元素。该方法利用 POD 从微观状态信息中提取宏观内部状态变量，从而丰富了用于在 TANN 框架内训练能量势能网络的宏观状态描述。TANN 提供的热力学一致性与 POD 的层次性相结合，可以再现复杂的非线性非弹性材料行为以及宏观地质力学系统响应。该方法通过复杂程度不断增加的应用进行了验证，证明了其再现高保真模拟数据的能力。提出的应用包括连续非弹性代表单元的均质化，以及推导岩土系统的宏观元素，该系统涉及承受水平荷载的粘土层中的单桩。最后，利用通过 POD 直接获得的投影算子轻松地重建了微观场。结果表明，POD-TANN 方法不仅能准确地再现所研究的构成响应，还能降低计算成本，使其成为异质非弹性地质力学系统多尺度建模的实用工具。
{"title":"A POD‐TANN Approach for the Multiscale Modeling of Materials and Macro‐Element Derivation in Geomechanics","authors":"Giovanni Piunno, Ioannis Stefanou, Cristina Jommi","doi":"10.1002/nag.3891","DOIUrl":"https://doi.org/10.1002/nag.3891","url":null,"abstract":"This paper introduces a novel approach that combines proper orthogonal decomposition (POD) with thermodynamics‐based artificial neural networks (TANNs) to capture the macroscopic behavior of complex inelastic systems and derive macro‐elements in geomechanics. The methodology leverages POD to extract macroscopic internal state variables from microscopic state information, thereby enriching the macroscopic state description used to train an energy potential network within the TANN framework. The thermodynamic consistency provided by TANN, combined with the hierarchical nature of POD, allows to reproduce complex, nonlinear inelastic material behaviors, as well as macroscopic geomechanical systems responses. The approach is validated through applications of increasing complexity, demonstrating its capability to reproduce high‐fidelity simulation data. The applications proposed include the homogenization of continuous inelastic representative unit cells and the derivation of a macro‐element for a geotechnical system involving a monopile in a clay layer subjected to horizontal loading. Eventually, the projection operators directly obtained via POD are exploited to easily reconstruct the microscopic fields. The results indicate that the POD‐TANN approach not only offers accuracy in reproducing the studied constitutive responses, but also reduces computational costs, making it a practical tool for the multiscale modeling of heterogeneous inelastic geomechanical systems.","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":"179 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142679005","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 modelling of rock structure is of great significance in characterizing rock characteristics and studying the failure laws of rock samples. In order to construct a high‐fidelity model of the rock structure efficiently, this paper proposes an adaptive mesh dissection algorithm based on the Voronoi structure. Image processing techniques, including greyscale, threshold segmentation and edge detection, are applied to simplify the original rock image into a feature edge image. Then, a probability density diagram of the feature image is generated, which provides a probabilistic basis for the subsequent spreading of mesh seed points. Moreover, the concept of polygonal representation rate and the mesh quality evaluation system of four‐dimensional metrics are established to suggest values for the seed point parameters of the initial mesh. The initial mesh is continuously optimized and iterated by barycentric iteration and gradient descent optimization methods to form mesh structural models with high representational performance efficiently. The model tests on particle, fracture and multi‐phase rock images show that the optimized mesh model is highly similar to the original image in terms of similarity and edge fit, and the algorithm significantly reduces the short‐edge rate and improves the shape regularity of the mesh structure. Finally, numerical tests of uniaxial compression are carried out based on the optimized mesh model. The results show that the model has computational potential in numerical calculations. This method builds a procedural structure from digital images to numerical models, which can provide a reliable model basis for simulating the physico‐mechanical behaviour of heterogeneous rocks.
{"title":"Adaptive Mesh Generation and Numerical Verification for Complex Rock Structures Based on Optimization and Iteration Algorithms","authors":"Huaiguang Xiao, Yueyang Li, Hengyang Wu, Lei He","doi":"10.1002/nag.3898","DOIUrl":"https://doi.org/10.1002/nag.3898","url":null,"abstract":"The modelling of rock structure is of great significance in characterizing rock characteristics and studying the failure laws of rock samples. In order to construct a high‐fidelity model of the rock structure efficiently, this paper proposes an adaptive mesh dissection algorithm based on the Voronoi structure. Image processing techniques, including greyscale, threshold segmentation and edge detection, are applied to simplify the original rock image into a feature edge image. Then, a probability density diagram of the feature image is generated, which provides a probabilistic basis for the subsequent spreading of mesh seed points. Moreover, the concept of polygonal representation rate and the mesh quality evaluation system of four‐dimensional metrics are established to suggest values for the seed point parameters of the initial mesh. The initial mesh is continuously optimized and iterated by barycentric iteration and gradient descent optimization methods to form mesh structural models with high representational performance efficiently. The model tests on particle, fracture and multi‐phase rock images show that the optimized mesh model is highly similar to the original image in terms of similarity and edge fit, and the algorithm significantly reduces the short‐edge rate and improves the shape regularity of the mesh structure. Finally, numerical tests of uniaxial compression are carried out based on the optimized mesh model. The results show that the model has computational potential in numerical calculations. This method builds a procedural structure from digital images to numerical models, which can provide a reliable model basis for simulating the physico‐mechanical behaviour of heterogeneous rocks.","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":"18 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142670563","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}
Alec Tristani, Lina‐María Guayacán‐Carrillo, Jean Sulem
Two‐dimensional analysis of tunnel design based on the convergence–confinement method, although commonly used in tunnel design, may not always be applied. For example, in squeezing grounds, if the support is installed very close to the tunnel face, three‐dimensional numerical modeling is required but is computationally expensive. Therefore, it is usually performed before or after tunnel excavation. A machine learning approach is presented here as an alternative to costly computations. Two surrogate models are developed based on synthetic data. The first model aims to assess the support pressure and the radial displacement at equilibrium in the lining and the radial displacement occurring close to the face at the installation distance of the support. The second model is intended to compute the extrusion of the core considering an unlined gallery. It is assumed a circular tunnel excavated in a Mohr–Coulomb elastoplastic perfectly plastic ground under an initial isotropic stress state. In particular, the bagging method is applied to neural networks to enhance the generalization capability of the models. A good performance is obtained using relatively scarce datasets. The modeling of the surrogate models is explained from the creation of the synthetic datasets to the evaluation of their performance. Their limitations are discussed. In practice, these two machine learning tools should be helpful in the field during the excavation phase.
{"title":"Data‐Driven Tools to Evaluate Support Pressure, Radial Displacements, and Face Extrusion for Tunnels Excavated in Elastoplastic Grounds","authors":"Alec Tristani, Lina‐María Guayacán‐Carrillo, Jean Sulem","doi":"10.1002/nag.3889","DOIUrl":"https://doi.org/10.1002/nag.3889","url":null,"abstract":"Two‐dimensional analysis of tunnel design based on the convergence–confinement method, although commonly used in tunnel design, may not always be applied. For example, in squeezing grounds, if the support is installed very close to the tunnel face, three‐dimensional numerical modeling is required but is computationally expensive. Therefore, it is usually performed before or after tunnel excavation. A machine learning approach is presented here as an alternative to costly computations. Two surrogate models are developed based on synthetic data. The first model aims to assess the support pressure and the radial displacement at equilibrium in the lining and the radial displacement occurring close to the face at the installation distance of the support. The second model is intended to compute the extrusion of the core considering an unlined gallery. It is assumed a circular tunnel excavated in a Mohr–Coulomb elastoplastic perfectly plastic ground under an initial isotropic stress state. In particular, the bagging method is applied to neural networks to enhance the generalization capability of the models. A good performance is obtained using relatively scarce datasets. The modeling of the surrogate models is explained from the creation of the synthetic datasets to the evaluation of their performance. Their limitations are discussed. In practice, these two machine learning tools should be helpful in the field during the excavation phase.","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":"1 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142645937","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}
Experiments and field monitoring have revealed that in block caving, fractures over the cave crown tend to form in narrow curved bands that are parallel or subparallel to the cave back surface. These fractures delineate curved shells of orebody between the bands and the cave back. The effectiveness of block caving hinges on the subsequent fracturing and fragmentation of these orebody shells. This study adopts a dual approach, combining thin spherical shell theory and full 3D numerical simulations along with principles of linear elastic fracture mechanics, to investigate the fracturing behaviour of these shells. Analytical analysis indicates that under axisymmetric loading, latitudinal tensile fractures predominantly initiate across the most part of the shell, occurring on both the upper and lower surfaces, except at a localised area. Additionally, longitudinal tensile fractures may initiate at the central area of the upper surface, while shear fractures tend to occur around the edge of the shell. Consequently, the shells become susceptible to fracturing, leading to the collapse or cave‐in of the orebody. Numerical simulations agree with these findings, illustrating that fracturing points within the shell region are longitudinally dispersed throughout the entire shell. Most of these fracturing points satisfy the criteria for tensile fracturing, particularly within the middle portion of the shell, aligning with the analytical results. Furthermore, simulations considering nonaxisymmetric loading patterns demonstrate that regions surrounding the caving cavity, aligned with the minimum principal in situ stress, exhibit heightened susceptibility to fracture initiation. This insight holds potential significance for optimising the design of the caving process.
{"title":"Analysis of Fracturing Above Block Caving Back: A Spherical Shell Theory Approach and BEM Numerical Simulation","authors":"Jingyu Shi, Baotang Shen","doi":"10.1002/nag.3893","DOIUrl":"https://doi.org/10.1002/nag.3893","url":null,"abstract":"Experiments and field monitoring have revealed that in block caving, fractures over the cave crown tend to form in narrow curved bands that are parallel or subparallel to the cave back surface. These fractures delineate curved shells of orebody between the bands and the cave back. The effectiveness of block caving hinges on the subsequent fracturing and fragmentation of these orebody shells. This study adopts a dual approach, combining thin spherical shell theory and full 3D numerical simulations along with principles of linear elastic fracture mechanics, to investigate the fracturing behaviour of these shells. Analytical analysis indicates that under axisymmetric loading, latitudinal tensile fractures predominantly initiate across the most part of the shell, occurring on both the upper and lower surfaces, except at a localised area. Additionally, longitudinal tensile fractures may initiate at the central area of the upper surface, while shear fractures tend to occur around the edge of the shell. Consequently, the shells become susceptible to fracturing, leading to the collapse or cave‐in of the orebody. Numerical simulations agree with these findings, illustrating that fracturing points within the shell region are longitudinally dispersed throughout the entire shell. Most of these fracturing points satisfy the criteria for tensile fracturing, particularly within the middle portion of the shell, aligning with the analytical results. Furthermore, simulations considering nonaxisymmetric loading patterns demonstrate that regions surrounding the caving cavity, aligned with the minimum principal in situ stress, exhibit heightened susceptibility to fracture initiation. This insight holds potential significance for optimising the design of the caving process.","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":"46 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142645936","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}
Hangli Gong, Mingyang Wang, Yi Luo, Tingting Liu, Ran Fan, Xinping Li
To investigate the stress‐confinement effect on the dynamic crack propagation and energy evolution characteristics of heterogeneous granite under impact loading, a three‐dimensional equivalent grain‐based model (3D‐GBM) and FLAC3D‐PFC3D coupled modeling technique was used to establish a numerical model of a full‐scale true triaxial Hopkinson test system. The results indicate that: (1) A rate‐effect model of the dynamic strength enhancement factor for heterogeneous rocks under multiaxial static and dynamic combined loading was constructed, with lateral stress confinement enhancing the sensitivity of dynamic strength to the strain rate. (2) Axial stress reduces the crack initiation stress ratio (σci/σd) and damage stress threshold ratio (σcd/σd), reducing the time to their onset, while lateral stress has the opposite effect. (3) Lateral stress confinement helps dynamically adjust the types of microcracks within the rock, restricts the relative slip friction between particles, and decreases the kinetic energy of failure. (4) At approximately the same strain rate, the strain energy and slip friction energy sequentially increase under uniaxial, biaxial, and triaxial stress confinement. The mutual slip friction and movement between rock particles are more intense under biaxial stress confinement compared to uniaxial conditions.
{"title":"Stress‐Confinement Effect on the Dynamic Mechanical Properties of Heterogeneous Granite Under Impact Loading: Experimental and Numerical Simulation","authors":"Hangli Gong, Mingyang Wang, Yi Luo, Tingting Liu, Ran Fan, Xinping Li","doi":"10.1002/nag.3896","DOIUrl":"https://doi.org/10.1002/nag.3896","url":null,"abstract":"To investigate the stress‐confinement effect on the dynamic crack propagation and energy evolution characteristics of heterogeneous granite under impact loading, a three‐dimensional equivalent grain‐based model (3D‐GBM) and FLAC<jats:sup>3D</jats:sup>‐PFC<jats:sup>3D</jats:sup> coupled modeling technique was used to establish a numerical model of a full‐scale true triaxial Hopkinson test system. The results indicate that: (1) A rate‐effect model of the dynamic strength enhancement factor for heterogeneous rocks under multiaxial static and dynamic combined loading was constructed, with lateral stress confinement enhancing the sensitivity of dynamic strength to the strain rate. (2) Axial stress reduces the crack initiation stress ratio (<jats:italic><jats:styled-content>σ</jats:styled-content></jats:italic><jats:sub>ci</jats:sub>/<jats:italic>σ</jats:italic><jats:sub>d</jats:sub>) and damage stress threshold ratio (<jats:italic>σ</jats:italic><jats:sub>cd</jats:sub>/<jats:italic>σ</jats:italic><jats:sub>d</jats:sub>), reducing the time to their onset, while lateral stress has the opposite effect. (3) Lateral stress confinement helps dynamically adjust the types of microcracks within the rock, restricts the relative slip friction between particles, and decreases the kinetic energy of failure. (4) At approximately the same strain rate, the strain energy and slip friction energy sequentially increase under uniaxial, biaxial, and triaxial stress confinement. The mutual slip friction and movement between rock particles are more intense under biaxial stress confinement compared to uniaxial conditions.","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":"13 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142637226","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}
A nonlinear variational auto‐encoder (NLVAE) is developed to reconstruct the plane strain stress field in a solid with embedded cracks subjected to uniaxial tension, uniaxial compression, and shear loading paths. Latent features are sampled from a skew‐normal distribution, which allows encoding marked variations of the features of the stress field across the load steps. The NLVAE is trained and tested based upon stress maps generated with the finite element method (FEM) with cohesive zone elements (CZEs). The NLVAE successfully captures stress concentrations that develop across the loading steps as a result of crack propagation, especially when enhanced disentanglement is emphasized during training. Some latent variables consistently emerge as significant across various microstructure descriptors and loading paths. Correlations observed between the evolution of fabric descriptors and that of their significant stress latent features indicate that the NLVAE can capture important microstructure transitions during the loading process. Crack connectivity, crack eccentricity, and the distribution of zones of highly connected opened cracks versus zones with no cracks are the fabric descriptors that best explain the sequences of latent features that are the most important for the reconstruction of the stress field. Notably, the distributional shape, tail behavior, and symmetry of microstructure descriptor distributions have more influence on the stress field than basic measures of central tendency and spread.
{"title":"Stress Field and Crack Pattern Interpretation by Deep Learning in a 2D Solid","authors":"Daniel Chou, Chloé Arson","doi":"10.1002/nag.3890","DOIUrl":"https://doi.org/10.1002/nag.3890","url":null,"abstract":"A nonlinear variational auto‐encoder (NLVAE) is developed to reconstruct the plane strain stress field in a solid with embedded cracks subjected to uniaxial tension, uniaxial compression, and shear loading paths. Latent features are sampled from a skew‐normal distribution, which allows encoding marked variations of the features of the stress field across the load steps. The NLVAE is trained and tested based upon stress maps generated with the finite element method (FEM) with cohesive zone elements (CZEs). The NLVAE successfully captures stress concentrations that develop across the loading steps as a result of crack propagation, especially when enhanced disentanglement is emphasized during training. Some latent variables consistently emerge as significant across various microstructure descriptors and loading paths. Correlations observed between the evolution of fabric descriptors and that of their significant stress latent features indicate that the NLVAE can capture important microstructure transitions during the loading process. Crack connectivity, crack eccentricity, and the distribution of zones of highly connected opened cracks versus zones with no cracks are the fabric descriptors that best explain the sequences of latent features that are the most important for the reconstruction of the stress field. Notably, the distributional shape, tail behavior, and symmetry of microstructure descriptor distributions have more influence on the stress field than basic measures of central tendency and spread.","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":"38 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142642578","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}
With the development of 3D discontinuous deformation analysis (DDA) in precise stress fields and crack propagation problems, it has also demonstrated outstanding capabilities in solving continuous–discontinuous problems. However, currently, 3D DDA modeling primarily focuses on generating rock joint networks and developing 3D cutting algorithms. Correspondingly, 3D geological modeling methods are not yet mature, and establishing 3D models often demands substantial time. The lack of supporting preprocessing modeling methods and corresponding visual operation interfaces significantly hampers the development of 3D DDA. This method builds upon advanced research achievements in unmanned aerial vehicle oblique photography, 3D reconstruction, 3D cutting, computer graphics, and visualization program design. This research establishes a 3D geological entity modeling method for 3D DDA and constructs a comprehensive program using relevant C++ libraries and C language interfaces. In this method, a 3D geological model that incorporates geological elements such as strata and faults is initially established using non‐uniform rational B‐splines (NURBSs) surfaces as the boundary of the solid model. Subsequently, finite element meshing is applied, followed by corresponding topology transformation, resulting in a 3D block system model suitable for 3D DDA calculation. To cater for diverse application scenarios, continuous–discontinuous models integrated with subblocks and models of arbitrary polyhedra can be established. The proposed method has been validated through several typical modeling examples, showing its ability to rapidly and generate 3D high‐precision geological reality models suitable for 3D DDA calculations. Additionally, some techniques used in this method can be extended for modeling other numerical simulation methods, warranting further research.
随着三维非连续变形分析（DDA）在精确应力场和裂缝扩展问题方面的发展，它在解决连续-非连续问题方面也表现出了卓越的能力。然而，目前三维 DDA 建模主要侧重于生成岩石节理网络和开发三维切割算法。相应地，三维地质建模方法尚未成熟，建立三维模型往往需要大量时间。缺乏配套的预处理建模方法和相应的可视化操作界面也极大地阻碍了三维 DDA 的发展。该方法建立在无人机倾斜摄影、三维重建、三维切割、计算机图形学和可视化程序设计等先进研究成果的基础上。该研究为三维 DDA 建立了一种三维地质实体建模方法，并利用相关的 C++ 库和 C 语言接口构建了一个综合程序。在该方法中，首先使用非均匀有理 B 样条（NURBS）曲面作为实体模型的边界，建立包含地层和断层等地质元素的三维地质模型。随后，应用有限元网格划分，并进行相应的拓扑转换，最终形成适合三维 DDA 计算的三维块体系统模型。为了满足不同的应用场景，可以建立与子块和任意多面体模型集成的连续-非连续模型。通过几个典型的建模实例验证了所提出的方法，表明该方法能够快速生成适合三维 DDA 计算的三维高精度地质现实模型。此外，该方法中使用的一些技术可扩展用于其他数值模拟方法的建模，值得进一步研究。
{"title":"Extension of a 3D Geological Entity Modeling Method for Discontinuous Deformation Analysis","authors":"Xing Wang, Xiaodong Fu, Qian Sheng, Jian Chen, Jingyu Kang, Jiaming Wu","doi":"10.1002/nag.3887","DOIUrl":"https://doi.org/10.1002/nag.3887","url":null,"abstract":"With the development of 3D discontinuous deformation analysis (DDA) in precise stress fields and crack propagation problems, it has also demonstrated outstanding capabilities in solving continuous–discontinuous problems. However, currently, 3D DDA modeling primarily focuses on generating rock joint networks and developing 3D cutting algorithms. Correspondingly, 3D geological modeling methods are not yet mature, and establishing 3D models often demands substantial time. The lack of supporting preprocessing modeling methods and corresponding visual operation interfaces significantly hampers the development of 3D DDA. This method builds upon advanced research achievements in unmanned aerial vehicle oblique photography, 3D reconstruction, 3D cutting, computer graphics, and visualization program design. This research establishes a 3D geological entity modeling method for 3D DDA and constructs a comprehensive program using relevant C++ libraries and C language interfaces. In this method, a 3D geological model that incorporates geological elements such as strata and faults is initially established using non‐uniform rational B‐splines (NURBSs) surfaces as the boundary of the solid model. Subsequently, finite element meshing is applied, followed by corresponding topology transformation, resulting in a 3D block system model suitable for 3D DDA calculation. To cater for diverse application scenarios, continuous–discontinuous models integrated with subblocks and models of arbitrary polyhedra can be established. The proposed method has been validated through several typical modeling examples, showing its ability to rapidly and generate 3D high‐precision geological reality models suitable for 3D DDA calculations. Additionally, some techniques used in this method can be extended for modeling other numerical simulation methods, warranting further research.","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":"8 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142642580","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}
To appropriately simulate the long‐term mechanical behavior of municipal solid waste (MSW), a constitutive model coupling the effects of biodegradation and fibrous reinforcement was developed. In the proposed model, the compressive deformation due to biodegradation was regarded as being caused by an additional equivalent stress. Considering the effect of biodegradation, an evolution equation of the equivalent stress was proposed, and a plastic volumetric strain hardening law was developed. A fibrous reinforcement parameter was introduced, which was associated with the fiber content, stress state, and plastic shear strain of MSW. A plastic shear strain hardening law was developed to model the fibrous reinforcement. Based on the associated flow rule and two plastic strain hardening laws, the proposed model was established. The proposed model well simulated the hardening properties of MSW, as evidenced by the stress‒strain curves and the consistent, nonlinear increase in volumetric strain with axial strain. The differences in the shear strength and volumetric deformation due to the confining stress and fiber content were also well simulated by the model. Furthermore, the model predictions accurately reflected the findings of experiments conducted over a period of 10 years. Finally, parametric investigations were used to calibrate this proposed model, which can well characterize the long‐term MSW mechanical behavior.
{"title":"Characterization of Long‐Term Municipal Solid Waste Constitutive Behavior With Coupled Biodegradation and Fibrous Reinforcing Effects","authors":"Xiulei Li, Chunwei Yang, Yuchen Zhang, Yuping Li, Jianyong Shi, Yanan Sun","doi":"10.1002/nag.3894","DOIUrl":"https://doi.org/10.1002/nag.3894","url":null,"abstract":"To appropriately simulate the long‐term mechanical behavior of municipal solid waste (MSW), a constitutive model coupling the effects of biodegradation and fibrous reinforcement was developed. In the proposed model, the compressive deformation due to biodegradation was regarded as being caused by an additional equivalent stress. Considering the effect of biodegradation, an evolution equation of the equivalent stress was proposed, and a plastic volumetric strain hardening law was developed. A fibrous reinforcement parameter was introduced, which was associated with the fiber content, stress state, and plastic shear strain of MSW. A plastic shear strain hardening law was developed to model the fibrous reinforcement. Based on the associated flow rule and two plastic strain hardening laws, the proposed model was established. The proposed model well simulated the hardening properties of MSW, as evidenced by the stress‒strain curves and the consistent, nonlinear increase in volumetric strain with axial strain. The differences in the shear strength and volumetric deformation due to the confining stress and fiber content were also well simulated by the model. Furthermore, the model predictions accurately reflected the findings of experiments conducted over a period of 10 years. Finally, parametric investigations were used to calibrate this proposed model, which can well characterize the long‐term MSW mechanical behavior.","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":"64 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142642579","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}
Suifeng Wang, Hideaki Yasuhara, Li Zhuang, Xianyu Zhao, Liping Zhang, Tao Wang
The anisotropy at the grain scale significantly impacts cracking behavior of crystalline rocks. However, the anisotropy of mineral structure, especially the grain shape and orientation has been inadequately addressed in studies on hydraulic fracturing. To bridge this gap, this paper introduces a coupled hydro‐grain‐texture model (HGTM) based on discrete element model (DEM) that investigates the influence of grain shape and orientation on fluid‐driven cracking processes in crystalline rock. The HGTM can consider the different mineral grain shapes and orientations by changing the aspect ratio and rotating coordinate axes. Our studies covered six distinct in‐situ stresses, three grain shapes, and five grain orientations. Initially, we present a comprehensive examination of the microcracking processes of hydraulic fracturing. Then the influences of in‐situ stress, grain shape, and grain orientation on cracking processes were studied. The results underscore that both mineral grain and in‐situ stress interplay to influence the hydraulic fracturing of the crystalline rocks. The proposed HGTM can well mimic the propagation process of hydraulic fracturing by comparing with the experimental results and the results reveal that hydraulic fracturing in crystalline rocks is a highly complex process. This research clarifies the complex interplay between grain texture and hydraulic fracturing, offering invaluable insights for optimizing stimulation practices.
{"title":"A Novel Hydro‐Grain‐Texture Model to Unveil the Impact of Mineral Grain Anisotropy on Fluid‐Driven Cracking Processes in Crystalline Rock","authors":"Suifeng Wang, Hideaki Yasuhara, Li Zhuang, Xianyu Zhao, Liping Zhang, Tao Wang","doi":"10.1002/nag.3888","DOIUrl":"https://doi.org/10.1002/nag.3888","url":null,"abstract":"The anisotropy at the grain scale significantly impacts cracking behavior of crystalline rocks. However, the anisotropy of mineral structure, especially the grain shape and orientation has been inadequately addressed in studies on hydraulic fracturing. To bridge this gap, this paper introduces a coupled hydro‐grain‐texture model (HGTM) based on discrete element model (DEM) that investigates the influence of grain shape and orientation on fluid‐driven cracking processes in crystalline rock. The HGTM can consider the different mineral grain shapes and orientations by changing the aspect ratio and rotating coordinate axes. Our studies covered six distinct in‐situ stresses, three grain shapes, and five grain orientations. Initially, we present a comprehensive examination of the microcracking processes of hydraulic fracturing. Then the influences of in‐situ stress, grain shape, and grain orientation on cracking processes were studied. The results underscore that both mineral grain and in‐situ stress interplay to influence the hydraulic fracturing of the crystalline rocks. The proposed HGTM can well mimic the propagation process of hydraulic fracturing by comparing with the experimental results and the results reveal that hydraulic fracturing in crystalline rocks is a highly complex process. This research clarifies the complex interplay between grain texture and hydraulic fracturing, offering invaluable insights for optimizing stimulation practices.","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":"35 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2024-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142597495","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}
Currently, our understanding of material‐scale deterioration resulting from meteorologically induced variations in pore water pressure and its significant impact on infrastructure slopes is limited. To bridge this knowledge gap, we have developed an extended kinematic hardening constitutive model for unsaturated soils that refines our understanding of weather‐driven deterioration mechanisms in heterogeneous clay soils. This model has the capability of predicting the irrecoverable degradation of strength and stiffness that has been shown to occur when soils undergo wetting and drying cycles. The model is equipped with a fully coupled and hysteretic water retention curve and a hysteretic loading–collapse curve and has the capability to predict the irrecoverable degradation of strength and stiffness that occurs during cyclic loading of soils. Here, we employ a fully implicit stress integration technique and give particular emphasis to deriving a consistent tangent operator, which includes the linearisation of the retention curve. The proposed algorithm is evaluated for efficiency and performance by simulating various stress and strain‐driven triaxial paths, and the accuracy of the integration technique is evaluated through the use of convergence curves.
{"title":"Formulation and Implicit Numerical Integration of a Kinematic Hardening Model for Unsaturated Soils","authors":"Lluís Monforte, Mohamed Rouainia","doi":"10.1002/nag.3878","DOIUrl":"https://doi.org/10.1002/nag.3878","url":null,"abstract":"Currently, our understanding of material‐scale deterioration resulting from meteorologically induced variations in pore water pressure and its significant impact on infrastructure slopes is limited. To bridge this knowledge gap, we have developed an extended kinematic hardening constitutive model for unsaturated soils that refines our understanding of weather‐driven deterioration mechanisms in heterogeneous clay soils. This model has the capability of predicting the irrecoverable degradation of strength and stiffness that has been shown to occur when soils undergo wetting and drying cycles. The model is equipped with a fully coupled and hysteretic water retention curve and a hysteretic loading–collapse curve and has the capability to predict the irrecoverable degradation of strength and stiffness that occurs during cyclic loading of soils. Here, we employ a fully implicit stress integration technique and give particular emphasis to deriving a consistent tangent operator, which includes the linearisation of the retention curve. The proposed algorithm is evaluated for efficiency and performance by simulating various stress and strain‐driven triaxial paths, and the accuracy of the integration technique is evaluated through the use of convergence curves.","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":"244 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2024-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142597485","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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