Particle strength is one of the critical factors that causes the degradation of the mechanical behaviour of crushable soil. Because of the complexity of particle shape, its effect on particle strength has not been completely comprehended. In this study, single particle crushing tests were performed on carbonate gravel particles with three size fractions (i.e., 5‒10 mm, 10‒15 mm and 15‒20 mm) and three shapes (i.e., blocky, rodlike and flaky), using a PartAn 3D Maxi large particle size and shape analyser to obtain the shape characteristics of the particles. The determination of crushing strength for particles with complex shapes was discussed, and it was found that it is appropriate to use the area equivalent circle diameter to obtain the crushing strength. The influence of particle size and shape parameters, including the elongation index, flatness index, intercept sphericity, circularity and convexity, on the crushing strength were identified, and an index named the form factor considering dimensions in three directions was proposed to describe the effect of particle shape. Based on this form factor, a probabilistic model was established to predict the distribution of crushing strength of carbonate gravel particles with various sizes and shapes. The proposed model could be used in the discrete element method to consider the influence of shape additionally when evaluating particle breakage.
颗粒强度是导致可破碎土力学性能退化的关键因素之一。由于颗粒形状的复杂性，其对颗粒强度的影响尚未完全了解。本研究采用PartAn 3D Maxi大粒度形状分析仪，对5-10 mm、10-15 mm和15-20 mm三种粒径段和块状、棒状和片状三种形状的碳酸盐砾石颗粒进行单粒破碎试验，获得颗粒的形状特征。对形状复杂的颗粒破碎强度的确定进行了讨论，发现用面积等效圆直径来计算破碎强度是合适的。确定了颗粒尺寸和形状参数(伸长率指数、平坦度指数、截距球度、圆度和凹凸度)对破碎强度的影响，提出了考虑三个方向尺寸的形状因子指标来描述颗粒形状对破碎强度的影响。在此基础上，建立了预测不同尺寸和形状碳酸盐碎石颗粒破碎强度分布的概率模型。该模型可用于离散元法中，在评估颗粒破碎时考虑形状的影响。
{"title":"Laboratory investigation on the single particle crushing strength of carbonate gravel incorporating size and shape effects","authors":"Xin Liu, Sa Li, Ting Yao","doi":"10.1680/jgeot.23.00038","DOIUrl":"https://doi.org/10.1680/jgeot.23.00038","url":null,"abstract":"Particle strength is one of the critical factors that causes the degradation of the mechanical behaviour of crushable soil. Because of the complexity of particle shape, its effect on particle strength has not been completely comprehended. In this study, single particle crushing tests were performed on carbonate gravel particles with three size fractions (i.e., 5‒10 mm, 10‒15 mm and 15‒20 mm) and three shapes (i.e., blocky, rodlike and flaky), using a PartAn 3D Maxi large particle size and shape analyser to obtain the shape characteristics of the particles. The determination of crushing strength for particles with complex shapes was discussed, and it was found that it is appropriate to use the area equivalent circle diameter to obtain the crushing strength. The influence of particle size and shape parameters, including the elongation index, flatness index, intercept sphericity, circularity and convexity, on the crushing strength were identified, and an index named the form factor considering dimensions in three directions was proposed to describe the effect of particle shape. Based on this form factor, a probabilistic model was established to predict the distribution of crushing strength of carbonate gravel particles with various sizes and shapes. The proposed model could be used in the discrete element method to consider the influence of shape additionally when evaluating particle breakage.","PeriodicalId":55098,"journal":{"name":"Geotechnique","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136346323","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The bearing capacity of soils are critical for the design and analysis of foundations. The classical solutions derived from methods of characteristics and bound theories are based on the rigid plasticity and associated flow rule, which may not be realistic for natural soils. The undrained shear strength of soft clays exhibits strain-softening and anisotropic behavior in the lab tests, which creates complexity to choose appropriate strength parameters in conventional design process. In addition, the stress-strain characters are non-associative and path dependent, which also affects the bearing capacity of soils. This paper investigates two classical stability problems (i.e. deeply embedded pile/pipe section, and rigid strip footing) using the finite element analysis and MIT-E3 soil model, and demonstrates the effects of stain-softening and strength anisotropy on the undrained bearing capacity of soils. The computed results are compared with analytical solutions and finite element limit analysis, as well as those from finite element analysis using conventional soil models. These findings have strong practical implications to predict the bearing capacity of foundations and interpret insitu tests.
{"title":"Effect of strain-softening and strength anisotropy on the undrained bearing capacity of non-associated clay","authors":"Yuepeng Dong","doi":"10.1680/jgeot.23.00034","DOIUrl":"https://doi.org/10.1680/jgeot.23.00034","url":null,"abstract":"The bearing capacity of soils are critical for the design and analysis of foundations. The classical solutions derived from methods of characteristics and bound theories are based on the rigid plasticity and associated flow rule, which may not be realistic for natural soils. The undrained shear strength of soft clays exhibits strain-softening and anisotropic behavior in the lab tests, which creates complexity to choose appropriate strength parameters in conventional design process. In addition, the stress-strain characters are non-associative and path dependent, which also affects the bearing capacity of soils. This paper investigates two classical stability problems (i.e. deeply embedded pile/pipe section, and rigid strip footing) using the finite element analysis and MIT-E3 soil model, and demonstrates the effects of stain-softening and strength anisotropy on the undrained bearing capacity of soils. The computed results are compared with analytical solutions and finite element limit analysis, as well as those from finite element analysis using conventional soil models. These findings have strong practical implications to predict the bearing capacity of foundations and interpret insitu tests.","PeriodicalId":55098,"journal":{"name":"Geotechnique","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136348440","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Experiences from previous earthquake events indicated that sands containing non-plastic (silt) or plastic (clay) fines are susceptible to liquefaction. These experiences underline the need for improving the fundamental understanding of the seismic behaviour of silty and clayey sands and for developing appropriate methods to evaluate their liquefaction potential. This paper presents an attempt to elucidate the integrated effects of fines (non-plastic silt and plastic clay) inclusion and degree of saturation on the cyclic behaviour and liquefaction resistance of sands based on systematic experiments. One of the notable findings of the study is that, apart from the familiar mode of cyclic mobility, clayey sand can also undergo flow-type failure under either fully or partially saturated conditions. The unified correlation between the cyclic resistance ratio (CRR) and the state parameter (ψ), established earlier for clean and silty sand in the framework of critical state soil mechanics (CSSM), is found to work for clayey sand as well. Furthermore, it is shown that the impact of saturation on the cyclic strength of clean and clayey sands can be reasonably characterised using the compression wave velocity normalized by the shear wave velocity.
{"title":"Liquefaction susceptibility of clayey sands under saturated and partially saturated conditions","authors":"Pedram Fardad Amini, Jun Yang","doi":"10.1680/jgeot.23.00100","DOIUrl":"https://doi.org/10.1680/jgeot.23.00100","url":null,"abstract":"Experiences from previous earthquake events indicated that sands containing non-plastic (silt) or plastic (clay) fines are susceptible to liquefaction. These experiences underline the need for improving the fundamental understanding of the seismic behaviour of silty and clayey sands and for developing appropriate methods to evaluate their liquefaction potential. This paper presents an attempt to elucidate the integrated effects of fines (non-plastic silt and plastic clay) inclusion and degree of saturation on the cyclic behaviour and liquefaction resistance of sands based on systematic experiments. One of the notable findings of the study is that, apart from the familiar mode of cyclic mobility, clayey sand can also undergo flow-type failure under either fully or partially saturated conditions. The unified correlation between the cyclic resistance ratio (CRR) and the state parameter (ψ), established earlier for clean and silty sand in the framework of critical state soil mechanics (CSSM), is found to work for clayey sand as well. Furthermore, it is shown that the impact of saturation on the cyclic strength of clean and clayey sands can be reasonably characterised using the compression wave velocity normalized by the shear wave velocity.","PeriodicalId":55098,"journal":{"name":"Geotechnique","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136348214","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The reuse of existing piles is a significant path to achieving low-carbon, resilient, and sustainable urban construction. However, some key issues in this area remain unresolved, especially with regard to the lateral interaction of new and existing piles. This study used centrifuge tests and numerical simulations to investigate the influence of the head fixity adjustment of existing piles on the lateral load response of new piles. The lateral load responses of new piles were compared for four conditions of the heads of existing piles, and the contributions of existing piles to new piles were examined. An extensive parametric study was conducted to quantify the relative contributions of the existing pile head fixity to the lateral load response of new piles for different variables, including new-existing pile spacings, displacements of new piles, restraints of heads of new piles, and soil properties. Finally, a practical method was developed for the design of laterally loaded new piles that considers the head fixity of existing piles. The results of this study provide a feasible way to enhance the contributions of existing piles to the lateral load responses of new piles through the adjustment of the fixities of existing pile heads.
{"title":"Influence of the head fixity adjustment of existing piles on the lateral load response of new piles","authors":"Hongjiang Li, Songyu Liu, Liyuan Tong, Dingwen Zhang","doi":"10.1680/jgeot.22.00325","DOIUrl":"https://doi.org/10.1680/jgeot.22.00325","url":null,"abstract":"The reuse of existing piles is a significant path to achieving low-carbon, resilient, and sustainable urban construction. However, some key issues in this area remain unresolved, especially with regard to the lateral interaction of new and existing piles. This study used centrifuge tests and numerical simulations to investigate the influence of the head fixity adjustment of existing piles on the lateral load response of new piles. The lateral load responses of new piles were compared for four conditions of the heads of existing piles, and the contributions of existing piles to new piles were examined. An extensive parametric study was conducted to quantify the relative contributions of the existing pile head fixity to the lateral load response of new piles for different variables, including new-existing pile spacings, displacements of new piles, restraints of heads of new piles, and soil properties. Finally, a practical method was developed for the design of laterally loaded new piles that considers the head fixity of existing piles. The results of this study provide a feasible way to enhance the contributions of existing piles to the lateral load responses of new piles through the adjustment of the fixities of existing pile heads.","PeriodicalId":55098,"journal":{"name":"Geotechnique","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135191968","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Owing to the complex morphology and the fragility of highly decomposed granite (HDG), it is still a challenge to track the breakage process of HDG particles within a deformed sample in geomechanics research. An HDG particle matching method is proposed in this paper for the first time to track and match HDG fragments with their mother particles from which they break off. First, the X-ray micro-computed tomography (μCT) images of HDG particles were acquired from a one-dimensional compression test and a certain number of HDG particles and fragments were selected and reconstructed. Second, the original and fracture surfaces of the fragments were identified and segmented. Then, the essential morphological features of the particles and fragments were represented with the key points. The neighbourhood information around the key points was encoded by the three-dimensional (3D) feature descriptor. Next, the mismatches were filtered out by the random sample consensus (RANSAC) algorithm based on the similarity of the local neighbourhood information. Finally, the influences of several parameters on the matching results were investigated. The capability and efficiency of the HDG particle matching method were demonstrated using the μCT data of ten HDG particles and 32 fragments that resulted from the crushing of these particles.
{"title":"Matching of crushed highly decomposed granite particles using 3D SHOT descriptors","authors":"Zhiren Zhu, Jianfeng Wang","doi":"10.1680/jgeot.23.00095","DOIUrl":"https://doi.org/10.1680/jgeot.23.00095","url":null,"abstract":"Owing to the complex morphology and the fragility of highly decomposed granite (HDG), it is still a challenge to track the breakage process of HDG particles within a deformed sample in geomechanics research. An HDG particle matching method is proposed in this paper for the first time to track and match HDG fragments with their mother particles from which they break off. First, the X-ray micro-computed tomography (μCT) images of HDG particles were acquired from a one-dimensional compression test and a certain number of HDG particles and fragments were selected and reconstructed. Second, the original and fracture surfaces of the fragments were identified and segmented. Then, the essential morphological features of the particles and fragments were represented with the key points. The neighbourhood information around the key points was encoded by the three-dimensional (3D) feature descriptor. Next, the mismatches were filtered out by the random sample consensus (RANSAC) algorithm based on the similarity of the local neighbourhood information. Finally, the influences of several parameters on the matching results were investigated. The capability and efficiency of the HDG particle matching method were demonstrated using the μCT data of ten HDG particles and 32 fragments that resulted from the crushing of these particles.","PeriodicalId":55098,"journal":{"name":"Geotechnique","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135191969","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study investigates the effect of rubber particles on biaxial shear responses of sand‒rubber mixtures (SRMs) using a multibody meshfree method, which enables the flexible and robust modelling of visco-elastic deformation of rubber particles. From the energy evolutions in SRMs with different rubber contents (RCs), including the incremental elastic strain energy, friction slipping dissipation, and damping dissipation, it is found that the slipping dissipation is much severer than damping dissipation for specimens with lower RC, but less significant for greater RC specimens during shearing. In addition, the fraction of incremental strain energy increases with RC. Further investigations on the evolutions of force chain networks of SRMs indicate that the incorporation of rubber particles facilitates the stability of strong force chains by mitigating particle rotations in the strong force chains and relative sliding in the weak contacts. It is observed that the energy transformation in sheared SRMs has strong correlation with their microstructural evolution.
{"title":"Shear behaviour of sand‒rubber mixtures: interpretation from energy transformation and force chain evolution","authors":"Ning Guo, Yihao Shi, Zheng Hu, Zhongxuan Yang","doi":"10.1680/jgeot.23.00043","DOIUrl":"https://doi.org/10.1680/jgeot.23.00043","url":null,"abstract":"This study investigates the effect of rubber particles on biaxial shear responses of sand‒rubber mixtures (SRMs) using a multibody meshfree method, which enables the flexible and robust modelling of visco-elastic deformation of rubber particles. From the energy evolutions in SRMs with different rubber contents (RCs), including the incremental elastic strain energy, friction slipping dissipation, and damping dissipation, it is found that the slipping dissipation is much severer than damping dissipation for specimens with lower RC, but less significant for greater RC specimens during shearing. In addition, the fraction of incremental strain energy increases with RC. Further investigations on the evolutions of force chain networks of SRMs indicate that the incorporation of rubber particles facilitates the stability of strong force chains by mitigating particle rotations in the strong force chains and relative sliding in the weak contacts. It is observed that the energy transformation in sheared SRMs has strong correlation with their microstructural evolution.","PeriodicalId":55098,"journal":{"name":"Geotechnique","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135539316","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Si Yuan Wu, Wendal Victor Yue, Zhongqi Quentin Yue
The ground conditions around an old tunnel in London Clay strata were extensively studied. The correlation between Measurement While Drilling (MWD) drilling parameters and drillhole investigation results, however, was not desirable due to the significant noise in the drilling speed. This paper re-examines the original MWD data published in the literature and addresses associated noise issue by transferring the data in depth-series into the data in time-series. The curve of drill-bit advancement depth with net drilling time can be visually divided into many linear segments. Each linear segment has a gradient or constant drilling speed and represents a homogeneous geomaterial zone with constant resistance to drill bit loading. The depth variation of the constant drilling speed zones is further compared and well verified with the depth variation of lithological strata units identified from rotary-cored samples. A strength grade system is also proposed based on the linear zoning results. A new rock quality designation is calculated from the thickness of the constant drilling speed zone for the London site and is compared with those at four other sites, which further enhances the understanding and confidence in the linear zoning result and the constant drilling speeds as resistant strengths associated with the lithological strata units in London Clay.
{"title":"On drilling speed of London Clay from MWD data with time-series algorithm for ground characterization","authors":"Si Yuan Wu, Wendal Victor Yue, Zhongqi Quentin Yue","doi":"10.1680/jgeot.22.00433","DOIUrl":"https://doi.org/10.1680/jgeot.22.00433","url":null,"abstract":"The ground conditions around an old tunnel in London Clay strata were extensively studied. The correlation between Measurement While Drilling (MWD) drilling parameters and drillhole investigation results, however, was not desirable due to the significant noise in the drilling speed. This paper re-examines the original MWD data published in the literature and addresses associated noise issue by transferring the data in depth-series into the data in time-series. The curve of drill-bit advancement depth with net drilling time can be visually divided into many linear segments. Each linear segment has a gradient or constant drilling speed and represents a homogeneous geomaterial zone with constant resistance to drill bit loading. The depth variation of the constant drilling speed zones is further compared and well verified with the depth variation of lithological strata units identified from rotary-cored samples. A strength grade system is also proposed based on the linear zoning results. A new rock quality designation is calculated from the thickness of the constant drilling speed zone for the London site and is compared with those at four other sites, which further enhances the understanding and confidence in the linear zoning result and the constant drilling speeds as resistant strengths associated with the lithological strata units in London Clay.","PeriodicalId":55098,"journal":{"name":"Geotechnique","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135480612","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Adopting a double-porosity macroscopic modelling framework, a general formulation of the effective stress in compacted bentonites is derived from basic thermodynamic principles. The formulation indicates that, when there is equilibrium between macrostructural and microstructural water, the effect of salinity is affected by a factor that is equal to the ratio of the overall bulk modulus of the soil to that of the aggregates. The analysis of many well-tested salinisation experiments has shown that it is advisable to account for this factor. In double porosity systems, this factor represents how the effect of salinity is attenuated as the increment of intra-aggregate porosity stabilises, and the increase in total porosity becomes almost equal to the increase in macrostructural porosity.
{"title":"Effect of salinity on the effective stress of compacted bentonites","authors":"Vicente Navarro, Laura Asensio","doi":"10.1680/jgeot.22.00251","DOIUrl":"https://doi.org/10.1680/jgeot.22.00251","url":null,"abstract":"Adopting a double-porosity macroscopic modelling framework, a general formulation of the effective stress in compacted bentonites is derived from basic thermodynamic principles. The formulation indicates that, when there is equilibrium between macrostructural and microstructural water, the effect of salinity is affected by a factor that is equal to the ratio of the overall bulk modulus of the soil to that of the aggregates. The analysis of many well-tested salinisation experiments has shown that it is advisable to account for this factor. In double porosity systems, this factor represents how the effect of salinity is attenuated as the increment of intra-aggregate porosity stabilises, and the increase in total porosity becomes almost equal to the increase in macrostructural porosity.","PeriodicalId":55098,"journal":{"name":"Geotechnique","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135872942","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
What is the influence of sample preparation method on shear wave velocity or associated small strain shear modulus (G 0 ) of silty sands is a question of considerable interest. This paper presents an attempt to address this question through a comprehensive experimental programme which covers four sample preparation methods. The experiments were conducted on clean Toyoura sand and its mixtures with two types of fines of different sizes. For each sample preparation method, a range of void ratio and confining stress was investigated so as to obtain a comprehensive view of the influence of sample preparation and its interplay with other factors. One of the notable findings is that, compared with clean sand, the difference of G 0 induced by different sample reconstitution methods can be much enlarged for silty sand, and the influence is coupled with the size disparity ratio of the mixtures. The reduction of G 0 due to the presence of fines also depends on sample preparation method and for smaller fines, the reduction is more significant. A careful examination of the X-ray images of the specimens made by different methods suggests that the observed effects are mainly associated with the different contact conditions of coarse and fine grains.
{"title":"Small strain shear modulus of silty sands: the role of sample preparation method","authors":"Yutang Chen, Jun Yang","doi":"10.1680/jgeot.23.00031","DOIUrl":"https://doi.org/10.1680/jgeot.23.00031","url":null,"abstract":"What is the influence of sample preparation method on shear wave velocity or associated small strain shear modulus (G 0 ) of silty sands is a question of considerable interest. This paper presents an attempt to address this question through a comprehensive experimental programme which covers four sample preparation methods. The experiments were conducted on clean Toyoura sand and its mixtures with two types of fines of different sizes. For each sample preparation method, a range of void ratio and confining stress was investigated so as to obtain a comprehensive view of the influence of sample preparation and its interplay with other factors. One of the notable findings is that, compared with clean sand, the difference of G 0 induced by different sample reconstitution methods can be much enlarged for silty sand, and the influence is coupled with the size disparity ratio of the mixtures. The reduction of G 0 due to the presence of fines also depends on sample preparation method and for smaller fines, the reduction is more significant. A careful examination of the X-ray images of the specimens made by different methods suggests that the observed effects are mainly associated with the different contact conditions of coarse and fine grains.","PeriodicalId":55098,"journal":{"name":"Geotechnique","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135873056","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents a surrogate-based Bayesian approach for updating the ground parameters within an application of the observational method in sequential excavation method (SEM) construction. A three-dimensional (3D) finite-difference model is used in the forward analysis to simulate SEM construction explicitly considering 3D multi-face excavation effects and ground–structure interaction. The polynomial-chaos Kriging (PCK) method was employed to provide a surrogate for the 3D finite-difference model to alleviate the cost of probabilistic analysis. The uncertain geotechnical parameters are updated during SEM construction through a progressive Bayesian updating procedure. Time-series observations of multiple types of measurements are used to form the likelihood function. The posterior distributions of the uncertain parameters are derived from the affine invariant ensemble sampling (AIES) algorithm. The proposed framework is illustrated through application to data from the Regional Connector Transit Corridor (RCTC) crossover cavern project constructed in downtown Los Angeles. The uncertainties of the geotechnical parameters were substantially reduced. The posterior estimations indicate higher elastic modulus and cohesion of the Fernando formation than what was assumed before the construction. The updated predictions of the ground surface, subsurface and structural deformations showed improvement in agreement with the field measurements through the continuous updating process.
{"title":"Updating model parameters and predictions in SEM tunneling using a surrogate-based Bayesian approach","authors":"Haotian Zheng, Michael Mooney, Marte Gutierrez","doi":"10.1680/jgeot.22.00299","DOIUrl":"https://doi.org/10.1680/jgeot.22.00299","url":null,"abstract":"This paper presents a surrogate-based Bayesian approach for updating the ground parameters within an application of the observational method in sequential excavation method (SEM) construction. A three-dimensional (3D) finite-difference model is used in the forward analysis to simulate SEM construction explicitly considering 3D multi-face excavation effects and ground–structure interaction. The polynomial-chaos Kriging (PCK) method was employed to provide a surrogate for the 3D finite-difference model to alleviate the cost of probabilistic analysis. The uncertain geotechnical parameters are updated during SEM construction through a progressive Bayesian updating procedure. Time-series observations of multiple types of measurements are used to form the likelihood function. The posterior distributions of the uncertain parameters are derived from the affine invariant ensemble sampling (AIES) algorithm. The proposed framework is illustrated through application to data from the Regional Connector Transit Corridor (RCTC) crossover cavern project constructed in downtown Los Angeles. The uncertainties of the geotechnical parameters were substantially reduced. The posterior estimations indicate higher elastic modulus and cohesion of the Fernando formation than what was assumed before the construction. The updated predictions of the ground surface, subsurface and structural deformations showed improvement in agreement with the field measurements through the continuous updating process.","PeriodicalId":55098,"journal":{"name":"Geotechnique","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135874448","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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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