International Journal for Numerical and Analytical Methods in Geomechanics最新文献

{"title":"Multi-scale mechanics of polydisperse granular materials: From micro-scale and wave propagation experiments to DEM analysis","authors":"Nallala S. C. Reddy,&nbsp;Huan He,&nbsp;Kostas Senetakis","doi":"10.1002/nag.3798","DOIUrl":"10.1002/nag.3798","url":null,"abstract":"<p>This paper presents a multiscale experimental study integrated with numerical simulations examining the mechanics of polydisperse granular mixtures composed of coarse-grained particles mixed with varying percentages of fines. The study includes macroscale wave propagation tests using bender elements on isotopically compressed granular samples to investigate the stiffness variation with changes in size ratio (SR) and fines content (FC). Empirical equations were developed to predict stiffness based on the experimental data, using the concept of equivalent void ratio to represent the influence of void ratio on stiffness. A newly introduced parameter called size disparity indicator was used to consider the coupled effects of size disparity and fines content on stiffness. Microscale assessment of the individual contacting grains revealed that stiffness (at grain scale) is affected by changes in grain size, even when the SR is less than 6, however, the experimental observations of the shear modulus behavior from the macroscale test results reveal minimal effect of FC. Furthermore, numerical simulations using the discrete element method were conducted on the polydisperse granular mixtures to demonstrate the coupled effect of SR and FC on the structural matrix formation, thereby influencing the force transfer among contacts resulting in varying stiffness behavior. Our findings provide valuable insights into the behavior of polydisperse granular mixtures in engineering applications.</p>","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141545844","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}

{"title":"Elastoplastic constitutive model for overconsolidated clays with an advanced dilatancy relation","authors":"Kehao Chen,&nbsp;Rui Pang,&nbsp;Bin Xu,&nbsp;Xingliang Wang","doi":"10.1002/nag.3803","DOIUrl":"10.1002/nag.3803","url":null,"abstract":"<p>The dilatancy behavior of overconsolidated (OC) clays is a key factor in determining their strength and deformation characteristics. Recognizing the limitations of previous dilatancy relations for OC clays, a novel dilatancy relation is proposed that can effectively capture the changes in dilatancy point, volume dilatancy and contraction with the overconsolidation ratio (OCR). As OC clays revert to the normally consolidated (NC) state, the proposed dilatancy relation smoothly transitions to that of the modified Cam-clay (MCC) model, ensuring a unified description of the dilatancy relation between OC and NC clays. The dilatancy relation can be easily incorporated into the constitutive model of different theoretical frameworks. Subsequently, this advanced dilatancy relation is integrated into a new elastoplastic constitutive model for OC clays within the framework of bounding surface and generalized plasticity theory. The validity of the proposed model is confirmed through drained triaxial compression and extension, undrained triaxial compression and extension, as well as complex stress path tests for clays with various OCRs, and the simulation results of the proposed model are compared with those of the SANICLAY model. The comparative analysis demonstrate that the model performs well in simulating the behavior of OC clays.</p>","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141521475","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}

{"title":"A two-stage combined filtration-consolidation model for slurry ground treated by vacuum preloading","authors":"Xiaoqian Ye,&nbsp;Li Shi,&nbsp;Yuanqiang Cai","doi":"10.1002/nag.3804","DOIUrl":"10.1002/nag.3804","url":null,"abstract":"<p>The vacuum preloading technique is extensively employed for ground improvement, particularly for slurry ground characterized by high-water content and low strength. Such ground frequently exhibits a delay in pore water pressure dissipation when treated with prefabricated vertical drains. To clarify the drainage and consolidation behaviour of high-water content slurry ground under vacuum preloading, this study proposed a two-stage combined model that integrates both filtration and consolidation processes. Initially, an axisymmetric filtration model was used to describe the formation of the soil column through the radial migration and compaction of the particles. The end-of-filtration radial distributions of void ratio, permeability coefficient, and effective pressure served as initial conditions for the consolidation stage analysis. This stage was depicted using a large strain consolidation model based on the free strain condition. The results showed the necessity of incorporating the filtration stage to capture the overall drainage mechanism and characteristics of slurry ground with vacuum preloading treatment.</p>","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141521759","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}

{"title":"Coupled model for electro-osmosis consolidation and ion transport considering chemical osmosis in saturated clay soils","authors":"Shangqi Ge,&nbsp;Wenhao Jiang,&nbsp;Ji-Peng Wang,&nbsp;Guohui Feng,&nbsp;Lingwei Zheng,&nbsp;Xinyu Xie","doi":"10.1002/nag.3802","DOIUrl":"10.1002/nag.3802","url":null,"abstract":"<p>The electro-osmosis approach efficiently facilitates the rapid dewatering of soil with high water content and contributes to reducing contaminant levels within the clay soil. However, the changes of chemical field caused by ion transport in the clay soil during electro-osmosis process will also influence the clay soil consolidation effect. Existing theories predominantly tend to disregard this crucial physical process and its resultant effects, thereby restraining a comprehensive analysis of electro-osmosis consolidation (EOC) behavior under intricate chemical conditions. This study introduces a concise model of EOC and ion transport considering chemical osmosis. The model considers the nonlinear variation of clay soil parameters such as compressibility, permeability, and effective diffusion coefficients, along with the interaction between EOC and ion transport. Meanwhile, the correctness of the model is verified from different aspects such as theoretical derivation and model comparison. Based on the proposed model, the impacts of the variation in electrical field intensity and chemical concentration on the coupled behaviors between EOC and ion transport are systematically investigated, with and without incorporating nonlinear consolidation characteristics. The results show that diffusion and electro-migration exhibit a more pronounced effect on ion transport during EOC. Simultaneously, with the increase of ion concentration in clay soil pore solution, the effects of chemical osmosis become increasingly apparent, thereby enhancing clay soil settlement.</p>","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141521760","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}

{"title":"Collapse characteristics of binary granular columns considering inhomogeneous particle size distributions","authors":"Hao Sun,&nbsp;Jun-Ze Jia,&nbsp;François Nicot,&nbsp;Xiao-Xiao Wang,&nbsp;Li-Shan Zhao","doi":"10.1002/nag.3799","DOIUrl":"10.1002/nag.3799","url":null,"abstract":"<p>Debris avalanches and dry granular flows exhibit similar characteristics. In order to comprehend the fundamental mechanisms and improve the accuracy in predicting disasters such as landslides, debris flows, and rock avalanches, the collapse characteristics of a binary granular column are investigated through a three-dimensional discrete element model. A novel approach is proposed by incorporating the concept of local granular velocity fluctuation and applying a cluster analysis method. Then, the flow mechanism of the binary granular column is analyzed, by considering the inhomogeneous particle size distribution. The research results show that: (1) The normalized final packing height of the granular column gradually increases when the content of coarse particles exceeds 20% and when the coarse-fine particle size ratio increases. Conversely, the normalized run-out distance of the granular column decreases gradually with the increase in coarse particle content and the coarse-fine particle size ratio. (2) The particles with higher granular velocity fluctuations tend to move together and form clusters, demonstrating dynamical heterogeneity. As the coarse particle content and coarse-fine particle size ratio increase, there is a greater tendency for particles to assemble into larger-scale active clusters. This means that a larger number of particles exhibit collective behavior during the collapse process, resulting in increased resistance to shear deformation. Ultimately, this leads to a greater packing height and a reduced run-out distance when observed from a macroscopic perspective.</p>","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141453070","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}

{"title":"Application of factorization machine with quantum annealing to hyperparameter optimization and metamodel-based optimization in granular flow simulations","authors":"Junsen Xiao,&nbsp;Katsuhiro Endo,&nbsp;Mayu Muramatsu,&nbsp;Reika Nomura,&nbsp;Shuji Moriguchi,&nbsp;Kenjiro Terada","doi":"10.1002/nag.3800","DOIUrl":"10.1002/nag.3800","url":null,"abstract":"<p>This study examined the applicability of factorization machines with quantum annealing (FMQA) to the field of landslide risk assessment for two specific black-box optimization problems, hyperparameter optimization (HPO) for metamodeling and metamodel-based simulation optimization (MBSO) targeting granular flow simulation using discrete element method (DEM). These two optimization problems are solved successively: HPO is first performed to determine the hyperparameters of the Gaussian process regression (GPR) metamodel, which is then used as a low-cost, fast approximate solver of granular flow simulations for MBSO. After conducting a series of granular flow simulations using DEM, a metamodel is created that outputs a risk index of interest, the run-out distance, from its input parameters by employing GPR with two hyperparameters, length-scale and signal variance. Subsequently, HPO is performed to obtain the optimal set of hyperparameters by applying FMQA and other optimization methods using another set of hyperparameters determined using the gradient-ascent method as the reference solution. Finally, using the metamodel created by each optimization method as an approximate solver for DEM simulations, MBSO is performed to find the optimal target output, the maximum run-out distance, in the space of physical input parameters for risk assessment. A comparison of the performance of FMQA with that of other methods shows that FMQA is competitive in terms of efficiency and stability with state-of-the-art algorithms such as Bayesian optimization.</p>","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/nag.3800","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141452867","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Emergence of critical state in granular materials using a variationally-based damage-elasto-plastic micromechanical continuum model","authors":"Nurettin Yilmaz,&nbsp;M. Erden Yildizdag,&nbsp;Francesco Fabbrocino,&nbsp;Luca Placidi,&nbsp;Anil Misra","doi":"10.1002/nag.3795","DOIUrl":"10.1002/nag.3795","url":null,"abstract":"<p>The mechanical response of granular materials, exemplified by frictional grain interactions, is characterized by a critical state in which deformation occurs without change of material volume or stresses when subjected to large shear deformation. In this work, a granular micromechanics approach (GMA) based continuum model is used to investigate the emergence of such a critical state. The continuum description is constructed through mechanical concepts based upon elastic and dissipation energies defined for a generic grain-pair interaction. A hemivariational principle provides the basis for considering the evolution of damage and plasticity phenomena comprising grain-pair contact loss and irreversible deformation. As a consequence, the Karush–Kuhn–Tucker (KKT)-type conditions are derived, which give the evolution equations for the irreversible phenomena. Notably, in this derivation there is no invocation of flow rules and other similar assumptions of classical phenomenological continuum damage and plasticity. Further, Piola's ansatz is elaborated to kinematically connect granular micromechanics of grain-pair to the continuum description. While the concept of critical state analysis has been handled with either phenomenological approaches or discrete numerical frameworks, in the present paper this concept is examined within a micromechanics-based continuum description. The constitutive model is established and the coupled damage and plastic irreversible quantities are assessed. The critical state is shown to emerge as grain-pair related damage and plastic evolution in a competitive/collaborative manner during the imposed loading path.</p>","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141448323","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}

{"title":"Competition among simultaneously stimulated multiple hydraulic fractures: Insights from DEM simulation with the consideration of fluid partitioning","authors":"Xuejian Li,&nbsp;Kang Duan,&nbsp;Moli Zhao,&nbsp;Qiangyong Zhang,&nbsp;Luchao Wang,&nbsp;Rihua Jiang","doi":"10.1002/nag.3801","DOIUrl":"10.1002/nag.3801","url":null,"abstract":"<p>Stimulating long and persistent fractures from multiple perforations in horizontal wells plays a vital role in enhancing the recovery of hydrocarbons from unconventional reservoirs. However, interaction among fractures may lead to dramatic nonuniformity, but the mechanism that drives the competition still eludes explanation. We proposed an improved two-dimensional discrete element model to simulate fluid competition and stress interaction among perforations in the same fracturing stage. The fluid partitioning is implemented by dynamically dividing the injected fluid into different perforations to maintain pressure consistency and fluid conservation. The model is validated by comparing the induced stress, fracture aperture, and the evolution of the fracture height and the injection pressure with theoretical models. The influences of the perforation friction, fluid viscosity and injection rate are examined systematically. Simulation results reveal that fluid competition tends to stimulate one dominant fracture with other perforations suppressed. The effect of increasing the perforation friction for promoting the fluid partitioning is not remarkable while using more viscous fracturing fluid helps to initiate more fractures at the perforations. With a higher injection rate all fractures can propagate to the borders but the asymmetrical fracture pattern cannot be avoided. Four typical fracture patterns are distinguished by changing operational parameters.</p>","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141448166","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}

{"title":"Thermo-hydro-mechanical coupled material point method for modeling freezing and thawing of porous media","authors":"Jidu Yu,&nbsp;Jidong Zhao,&nbsp;Shiwei Zhao,&nbsp;Weijian Liang","doi":"10.1002/nag.3794","DOIUrl":"10.1002/nag.3794","url":null,"abstract":"<p>Climate warming accelerates permafrost thawing, causing warming-driven disasters like ground collapse and retrogressive thaw slump (RTS). These phenomena, involving intricate multiphysics interactions, phase transitions, nonlinear mechanical responses, and fluid-like deformations, and pose increasing risks to geo-infrastructures in cold regions. This study develops a thermo-hydro-mechanical (THM) coupled single-point three-phase material point method (MPM) to simulate the time-dependent phase transition and large deformation behavior arising from the thawing or freezing of ice/water in porous media. The mathematical framework is established based on the multiphase mixture theory in which the ice phase is treated as a solid constituent playing the role of skeleton together with soil grains. The additional strength due to ice cementation is characterized via an ice saturation-dependent Mohr–Coulomb model. The coupled formulations are solved using a fractional-step-based semi-implicit integration algorithm, which can offer both satisfactory numerical stability and computational efficiency when dealing with nearly incompressible fluids and extremely low permeability conditions in frozen porous media. Two hydro-thermal coupling cases, that is, frozen inclusion thaw and Talik closure/opening, are first benchmarked to show the method can correctly simulate both conduction- and convection-dominated thermal regimes in frozen porous systems. The fully THM responses are further validated by simulating a 1D thaw consolidation and a 2D rock freezing example. Good agreements with experimental results are achieved, and the impact of hydro-thermal variations on the mechanical responses, including thaw settlement and frost heave, are successfully captured. Finally, the predictive capability of the multiphysics MPM framework in simulating thawing-triggered large deformation and failure is demonstrated by modeling an RTS and the settlement of a strip footing on thawing ground.</p>","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/nag.3794","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141448233","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multi-objective reliability-based robust design for a rock tunnel support system using Pareto optimality","authors":"Zheming Zhang,&nbsp;Sikan Li,&nbsp;Yu Zhang,&nbsp;Yifeng Zhou,&nbsp;Jian Ji","doi":"10.1002/nag.3796","DOIUrl":"10.1002/nag.3796","url":null,"abstract":"<p>In the context of rock material and modeling uncertainties, the optimization of rock tunnel support systems is often conducted by selecting the most cost-effective solution among several feasible options that typically rely on the engineer's experience, potentially leading to overlooking the most optimal design. To improve such a limitation, this paper presents a multi-objective reliability-based robust design, considering the cost, safety, and design robustness systematically while maintaining the computational efficiency. In this framework, the uncertainty-based reliability constrains is performed using the first-order reliability method (FORM) and an improved Hasofer–Lind–Rackwits–Fiessler recursive algorithm (iHLRF-x). The design robustness, in terms of sensitivity index (SI), is evaluated using the normalized gradient of the system response to the noise factors, which can be efficiently obtained from the output of FORM analysis. Then, the Pareto front revealing the tradeoff between multiple objectives can be directly generated using the proposed optimization framework. To illustrate the effectiveness of this procedure, a set of the optimal design combinations of the shotcrete thickness and installation position for the exampled rock tunnel are obtained, and new perspectives pertaining the success of the reliability-based robust designs are provided.</p>","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/nag.3796","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141448359","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}