In most coastal and estuarine areas, tides easily cause surface erosion and even slope failure, resulting in severe land losses, deterioration of coastal infrastructure, and increased floods. The bio-cementation technique has been previously demonstrated to effectively improve the erosion resistance of slopes. Seawater contains magnesium ions (Mg2+) with a higher concentration than calcium ions (Ca2+); therefore, Mg2+ and Ca2+ were used together for bio-cementation in this study at various Mg2+/Ca2+ ratios as the microbially induced magnesium and calcium precipitation (MIMCP) treatment. Slope angles, surface strengths, precipitation contents, major phases, and microscopic characteristics of precipitation were used to evaluate the treatment effects. Results showed that the MIMCP treatment markedly enhanced the erosion resistance of slopes. Decreased Mg2+/Ca2+ ratios resulted in a smaller change in angles and fewer soil losses, especially the Mg2+ concentration below 0.2 M. The decreased Mg2+/Ca2+ ratio achieved increased precipitation contents, which contributed to better erosion resistance and higher surface strengths. Additionally, the production of aragonite would benefit from elevated Mg2+ concentrations and a higher Ca2+ concentration led to more nesquehonite in magnesium precipitation crystals. The slopes with an initial angle of 53° had worse erosion resistance than the slopes with an initial angle of 35°, but the Mg2+/Ca2+ ratios of 0.2:0.8, 0.1:0.9, and 0:1.0 were effective for both slope stabilization and erosion mitigation to a great extent. The results are of great significance for the application of MIMCP to improve erosion resistance of foreshore slopes and the MIMCP technique has promising application potential in marine engineering.
{"title":"Bio-cementation for tidal erosion resistance improvement of foreshore slopes based on microbially induced magnesium and calcium precipitation","authors":"Xiaohao Sun, Junjie Wang, Hengxing Wang, Linchang Miao, Ziming Cao, Linyu Wu","doi":"10.1016/j.jrmge.2023.08.009","DOIUrl":"https://doi.org/10.1016/j.jrmge.2023.08.009","url":null,"abstract":"In most coastal and estuarine areas, tides easily cause surface erosion and even slope failure, resulting in severe land losses, deterioration of coastal infrastructure, and increased floods. The bio-cementation technique has been previously demonstrated to effectively improve the erosion resistance of slopes. Seawater contains magnesium ions (Mg2+) with a higher concentration than calcium ions (Ca2+); therefore, Mg2+ and Ca2+ were used together for bio-cementation in this study at various Mg2+/Ca2+ ratios as the microbially induced magnesium and calcium precipitation (MIMCP) treatment. Slope angles, surface strengths, precipitation contents, major phases, and microscopic characteristics of precipitation were used to evaluate the treatment effects. Results showed that the MIMCP treatment markedly enhanced the erosion resistance of slopes. Decreased Mg2+/Ca2+ ratios resulted in a smaller change in angles and fewer soil losses, especially the Mg2+ concentration below 0.2 M. The decreased Mg2+/Ca2+ ratio achieved increased precipitation contents, which contributed to better erosion resistance and higher surface strengths. Additionally, the production of aragonite would benefit from elevated Mg2+ concentrations and a higher Ca2+ concentration led to more nesquehonite in magnesium precipitation crystals. The slopes with an initial angle of 53° had worse erosion resistance than the slopes with an initial angle of 35°, but the Mg2+/Ca2+ ratios of 0.2:0.8, 0.1:0.9, and 0:1.0 were effective for both slope stabilization and erosion mitigation to a great extent. The results are of great significance for the application of MIMCP to improve erosion resistance of foreshore slopes and the MIMCP technique has promising application potential in marine engineering.","PeriodicalId":54219,"journal":{"name":"Journal of Rock Mechanics and Geotechnical Engineering","volume":"52 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135509919","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}
Rock and geotechnical engineering investigations involve drilling holes in ground with or without retrieving soil and rock samples to construct the subsurface ground profile. On the basis of an actual soil nailing drilling for a slope stability project in Hong Kong, this paper further develops the drilling process monitoring (DPM) method for digitally profiling the subsurface geomaterials of weathered granitic rocks using a compressed airflow driven percussive-rotary drilling machine with down-the-hole (DTH) hammer. Seven transducers are installed on the drilling machine and record the chuck displacement, DTH rotational speed, and five pressures from five compressed airflows in real-time series. The mechanism and operations of the drilling machine are elaborated in detail, which is essential for understanding and evaluating the drilling data. A MATLAB program is developed to automatically filter the recorded drilling data in time series and classify them into different drilling processes in sub-time series. These processes include penetration, push-in with or without rod, pull-back with or without rod, rod-tightening and rod-untightening. The drilling data are further reconstructed to plot the curve of drill-bit depth versus the net drilling time along each of the six drillholes. Each curve is found to contain multiple linear segments with a constant penetration rate, which implies a zone of homogenous geomaterial with different weathering grades. The effect from fluctuation of the applied pressures is evaluated quantitatively. Detailed analyses are presented for accurately assess and verify the underground profiling and strength in weathered granitic rock, which provided the basis of using DPM method to confidently assess drilling measurements to interpret the subsurface profile in real time.
{"title":"Digital monitoring of rotary-percussive drilling with down-the-hole hammer for profiling weathered granitic ground","authors":"Wendal Victor Yue, Siyuan Wu, Manchao He, Yafei Qiao, Zhongqi Quentin Yue","doi":"10.1016/j.jrmge.2023.08.006","DOIUrl":"https://doi.org/10.1016/j.jrmge.2023.08.006","url":null,"abstract":"Rock and geotechnical engineering investigations involve drilling holes in ground with or without retrieving soil and rock samples to construct the subsurface ground profile. On the basis of an actual soil nailing drilling for a slope stability project in Hong Kong, this paper further develops the drilling process monitoring (DPM) method for digitally profiling the subsurface geomaterials of weathered granitic rocks using a compressed airflow driven percussive-rotary drilling machine with down-the-hole (DTH) hammer. Seven transducers are installed on the drilling machine and record the chuck displacement, DTH rotational speed, and five pressures from five compressed airflows in real-time series. The mechanism and operations of the drilling machine are elaborated in detail, which is essential for understanding and evaluating the drilling data. A MATLAB program is developed to automatically filter the recorded drilling data in time series and classify them into different drilling processes in sub-time series. These processes include penetration, push-in with or without rod, pull-back with or without rod, rod-tightening and rod-untightening. The drilling data are further reconstructed to plot the curve of drill-bit depth versus the net drilling time along each of the six drillholes. Each curve is found to contain multiple linear segments with a constant penetration rate, which implies a zone of homogenous geomaterial with different weathering grades. The effect from fluctuation of the applied pressures is evaluated quantitatively. Detailed analyses are presented for accurately assess and verify the underground profiling and strength in weathered granitic rock, which provided the basis of using DPM method to confidently assess drilling measurements to interpret the subsurface profile in real time.","PeriodicalId":54219,"journal":{"name":"Journal of Rock Mechanics and Geotechnical Engineering","volume":"162 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135325451","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}
Pub Date : 2023-11-01DOI: 10.1016/j.jrmge.2023.07.019
Akram Deiminiat, Jonathan D. Aubertin, Yannic Ethier
Conventional numerical solutions developed to describe the geomechanical behavior of rock interfaces subjected to differential load emphasize peak and residual shear strengths. The detailed analysis of pre- and post-peak shear stress-displacement behavior is central to various time-dependent and dynamic rock mechanic problems such as rockbursts and structural instabilities in highly stressed conditions. The complete stress-displacement surface (CSDS) model was developed to describe analytically the pre- and post-peak behavior of rock interfaces under differential loads. Original formulations of the CSDS model required extensive curve-fitting iterations which limited its practical applicability and transparent integration into engineering tools. The present work proposes modifications to the CSDS model aimed at developing a comprehensive and modern calibration protocol to describe the complete shear stress-displacement behavior of rock interfaces under differential loads. The proposed update to the CSDS model incorporates the concept of mobilized shear strength to enhance the post-peak formulations. Barton's concepts of joint roughness coefficient (JRC) and joint compressive strength (JCS) are incorporated to facilitate empirical estimations for peak shear stress and normal closure relations. Triaxial/uniaxial compression test and direct shear test results are used to validate the updated model and exemplify the proposed calibration method. The results illustrate that the revised model successfully predicts the post-peak and complete axial stress–strain and shear stress–displacement curves for rock joints.
{"title":"On the calibration of a shear stress criterion for rock joints to represent the full stress-strain profile","authors":"Akram Deiminiat, Jonathan D. Aubertin, Yannic Ethier","doi":"10.1016/j.jrmge.2023.07.019","DOIUrl":"https://doi.org/10.1016/j.jrmge.2023.07.019","url":null,"abstract":"Conventional numerical solutions developed to describe the geomechanical behavior of rock interfaces subjected to differential load emphasize peak and residual shear strengths. The detailed analysis of pre- and post-peak shear stress-displacement behavior is central to various time-dependent and dynamic rock mechanic problems such as rockbursts and structural instabilities in highly stressed conditions. The complete stress-displacement surface (CSDS) model was developed to describe analytically the pre- and post-peak behavior of rock interfaces under differential loads. Original formulations of the CSDS model required extensive curve-fitting iterations which limited its practical applicability and transparent integration into engineering tools. The present work proposes modifications to the CSDS model aimed at developing a comprehensive and modern calibration protocol to describe the complete shear stress-displacement behavior of rock interfaces under differential loads. The proposed update to the CSDS model incorporates the concept of mobilized shear strength to enhance the post-peak formulations. Barton's concepts of joint roughness coefficient (JRC) and joint compressive strength (JCS) are incorporated to facilitate empirical estimations for peak shear stress and normal closure relations. Triaxial/uniaxial compression test and direct shear test results are used to validate the updated model and exemplify the proposed calibration method. The results illustrate that the revised model successfully predicts the post-peak and complete axial stress–strain and shear stress–displacement curves for rock joints.","PeriodicalId":54219,"journal":{"name":"Journal of Rock Mechanics and Geotechnical Engineering","volume":"22 11","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135455893","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}
Pub Date : 2023-11-01DOI: 10.1016/j.jrmge.2023.04.025
Hanyan Wang, Qinyong Ma, Qianyun Wu
Lunar base construction is a crucial component of the lunar exploration program, and considering the dynamic characteristics of lunar soil is important for moon construction. Therefore, investigating the dynamic properties of lunar soil by establishing a constitutive relationship is critical for providing a theoretical basis for its damage evolution. In this paper, a split Hopkinson pressure bar (SHPB) device was used to perform three sets of impact tests under different pressures on a lunar soil simulant geopolymer (LSSG) with sodium silicate (Na2SiO3) contents of 1%, 3%, 5% and 7%. The dynamic stress–strain curves, failure modes, and energy variation rules of LSSG under different pressures were obtained. The equation was modified based on the ZWT viscoelastic constitutive model and was combined with the damage variable. The damage element obeys the Weibull distribution and the constitutive equation that can describe the mechanical properties of LSSG under dynamic loading was obtained. The results demonstrate that the dynamic compressive strength of LSSG has a marked strain-rate strengthening effect. Na2SiO3 has both strengthening and deterioration effects on the dynamic compressive strength of LSSG. As Na2SiO3 grows, the dynamic compressive strength of LSSG first increases and then decreases. At a fixed air pressure, 5% Na2SiO3 had the largest dynamic compressive strength, the largest incident energy, the smallest absorbed energy, and the lightest damage. The ZWT equation was modified according to the stress response properties of LSSG and the range of the SHPB strain rate to obtain the constitutive equation of the LSSG, and the model's correctness was confirmed.
{"title":"Damage constitutive model of lunar soil simulant geopolymer under impact loading","authors":"Hanyan Wang, Qinyong Ma, Qianyun Wu","doi":"10.1016/j.jrmge.2023.04.025","DOIUrl":"https://doi.org/10.1016/j.jrmge.2023.04.025","url":null,"abstract":"Lunar base construction is a crucial component of the lunar exploration program, and considering the dynamic characteristics of lunar soil is important for moon construction. Therefore, investigating the dynamic properties of lunar soil by establishing a constitutive relationship is critical for providing a theoretical basis for its damage evolution. In this paper, a split Hopkinson pressure bar (SHPB) device was used to perform three sets of impact tests under different pressures on a lunar soil simulant geopolymer (LSSG) with sodium silicate (Na2SiO3) contents of 1%, 3%, 5% and 7%. The dynamic stress–strain curves, failure modes, and energy variation rules of LSSG under different pressures were obtained. The equation was modified based on the ZWT viscoelastic constitutive model and was combined with the damage variable. The damage element obeys the Weibull distribution and the constitutive equation that can describe the mechanical properties of LSSG under dynamic loading was obtained. The results demonstrate that the dynamic compressive strength of LSSG has a marked strain-rate strengthening effect. Na2SiO3 has both strengthening and deterioration effects on the dynamic compressive strength of LSSG. As Na2SiO3 grows, the dynamic compressive strength of LSSG first increases and then decreases. At a fixed air pressure, 5% Na2SiO3 had the largest dynamic compressive strength, the largest incident energy, the smallest absorbed energy, and the lightest damage. The ZWT equation was modified according to the stress response properties of LSSG and the range of the SHPB strain rate to obtain the constitutive equation of the LSSG, and the model's correctness was confirmed.","PeriodicalId":54219,"journal":{"name":"Journal of Rock Mechanics and Geotechnical Engineering","volume":"55 5","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135765139","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}
As a calculation method based on the Galerkin variation, the numerical manifold method (NMM) adopts a double covering system, which can easily deal with discontinuous deformation problems and has a high calculation accuracy. Aiming at the thermo-mechanical (TM) coupling problem of fractured rock masses, this study uses the NMM to simulate the processes of crack initiation and propagation in a rock mass under the influence of temperature field, deduces related system equations, and proposes a penalty function method to deal with boundary conditions. Numerical examples are employed to confirm the effectiveness and high accuracy of this method. By the thermal stress analysis of a thick-walled cylinder (TWC), the simulation of cracking in the TWC under heating and cooling conditions, and the simulation of thermal cracking of the Swedish Äspö Pillar Stability Experiment (APSE) rock column, the thermal stress, and TM coupling are obtained. The numerical simulation results are in good agreement with the test data and other numerical results, thus verifying the effectiveness of the NMM in dealing with thermal stress and crack propagation problems of fractured rock masses.
{"title":"Numerical manifold method for thermo-mechanical coupling simulation of fractured rock mass","authors":"Jiawei Liang, Defu Tong, Fei Tan, Xiongwei Yi, Junpeng Zou, Jiahe Lv","doi":"10.1016/j.jrmge.2023.07.020","DOIUrl":"https://doi.org/10.1016/j.jrmge.2023.07.020","url":null,"abstract":"As a calculation method based on the Galerkin variation, the numerical manifold method (NMM) adopts a double covering system, which can easily deal with discontinuous deformation problems and has a high calculation accuracy. Aiming at the thermo-mechanical (TM) coupling problem of fractured rock masses, this study uses the NMM to simulate the processes of crack initiation and propagation in a rock mass under the influence of temperature field, deduces related system equations, and proposes a penalty function method to deal with boundary conditions. Numerical examples are employed to confirm the effectiveness and high accuracy of this method. By the thermal stress analysis of a thick-walled cylinder (TWC), the simulation of cracking in the TWC under heating and cooling conditions, and the simulation of thermal cracking of the Swedish Äspö Pillar Stability Experiment (APSE) rock column, the thermal stress, and TM coupling are obtained. The numerical simulation results are in good agreement with the test data and other numerical results, thus verifying the effectiveness of the NMM in dealing with thermal stress and crack propagation problems of fractured rock masses.","PeriodicalId":54219,"journal":{"name":"Journal of Rock Mechanics and Geotechnical Engineering","volume":"50 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135515219","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}
Karst fracture-cavity carbonate reservoirs, in which natural cavities are connected by natural fractures to form cavity clusters in many circumstances, have become significant fields of oil and gas exploration and exploitation. Proppant fracturing is considered as the best method for exploiting carbonate reservoirs; however, previous studies primarily focused on the effects of individual types of geological formations, such as natural fractures or cavities, on fracture propagation. In this study, true-triaxial physical simulation experiments were systematically performed under four types of stress difference conditions after the accurate prefabrication of four types of different fracture-cavity distributions in artificial samples. Subsequently, the interaction mechanism between the hydraulic fractures and fracture-cavity structures was systematically analyzed in combination with the stress distribution, cross-sectional morphology of the main propagation path, and three-dimensional visualization of the overall fracture network. It was found that the propagation of hydraulic fractures near the cavity was inhibited by the stress concentration surrounding the cavity. In contrast, a natural fracture with a smaller approach angle (0° and 30°) around the cavity can alleviate the stress concentration and significantly facilitate the connection with the cavity. In addition, the hydraulic fracture crossed the natural fracture at the 45° approach angle and bypassed the cavity under higher stress difference conditions. A new stimulation effectiveness evaluation index was established based on the stimulated reservoir area (SRA), tortuosity of the hydraulic fractures (T), and connectivity index (CI) of the cavities. These findings provide new insights into the fracturing design of carbonate reservoirs.
{"title":"Visualization and characterization of experimental hydraulic fractures interacting with karst fracture-cavity distributions","authors":"Hanzhi Yang, Xin Chang, Chunhe Yang, Wuhao Guo, Lei Wang, Guokai Zhao, Yintong Guo","doi":"10.1016/j.jrmge.2023.08.010","DOIUrl":"https://doi.org/10.1016/j.jrmge.2023.08.010","url":null,"abstract":"Karst fracture-cavity carbonate reservoirs, in which natural cavities are connected by natural fractures to form cavity clusters in many circumstances, have become significant fields of oil and gas exploration and exploitation. Proppant fracturing is considered as the best method for exploiting carbonate reservoirs; however, previous studies primarily focused on the effects of individual types of geological formations, such as natural fractures or cavities, on fracture propagation. In this study, true-triaxial physical simulation experiments were systematically performed under four types of stress difference conditions after the accurate prefabrication of four types of different fracture-cavity distributions in artificial samples. Subsequently, the interaction mechanism between the hydraulic fractures and fracture-cavity structures was systematically analyzed in combination with the stress distribution, cross-sectional morphology of the main propagation path, and three-dimensional visualization of the overall fracture network. It was found that the propagation of hydraulic fractures near the cavity was inhibited by the stress concentration surrounding the cavity. In contrast, a natural fracture with a smaller approach angle (0° and 30°) around the cavity can alleviate the stress concentration and significantly facilitate the connection with the cavity. In addition, the hydraulic fracture crossed the natural fracture at the 45° approach angle and bypassed the cavity under higher stress difference conditions. A new stimulation effectiveness evaluation index was established based on the stimulated reservoir area (SRA), tortuosity of the hydraulic fractures (T), and connectivity index (CI) of the cavities. These findings provide new insights into the fracturing design of carbonate reservoirs.","PeriodicalId":54219,"journal":{"name":"Journal of Rock Mechanics and Geotechnical Engineering","volume":"52 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135564681","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}
Pub Date : 2023-11-01DOI: 10.1016/j.jrmge.2023.08.011
Akshay Kumar, Gaurav Tiwari
Traditional global sensitivity analysis (GSA) neglects the epistemic uncertainties associated with the probabilistic characteristics (i.e. type of distribution type and its parameters) of input rock properties emanating due to the small size of datasets while mapping the relative importance of properties to the model response. This paper proposes an augmented Bayesian multi-model inference (BMMI) coupled with GSA methodology (BMMI-GSA) to address this issue by estimating the imprecision in the moment-independent sensitivity indices of rock structures arising from the small size of input data. The methodology employs BMMI to quantify the epistemic uncertainties associated with model type and parameters of input properties. The estimated uncertainties are propagated in estimating imprecision in moment-independent Borgonovo's indices by employing a reweighting approach on candidate probabilistic models. The proposed methodology is showcased for a rock slope prone to stress-controlled failure in the Himalayan region of India. The proposed methodology was superior to the conventional GSA (neglects all epistemic uncertainties) and Bayesian coupled GSA (B-GSA) (neglects model uncertainty) due to its capability to incorporate the uncertainties in both model type and parameters of properties. Imprecise Borgonovo's indices estimated via proposed methodology provide the confidence intervals of the sensitivity indices instead of their fixed-point estimates, which makes the user more informed in the data collection efforts. Analyses performed with the varying sample sizes suggested that the uncertainties in sensitivity indices reduce significantly with the increasing sample sizes. The accurate importance ranking of properties was only possible via samples of large sizes. Further, the impact of the prior knowledge in terms of prior ranges and distributions was significant; hence, any related assumption should be made carefully.
{"title":"A Bayesian multi-model inference methodology for imprecise moment-independent global sensitivity analysis of rock structures","authors":"Akshay Kumar, Gaurav Tiwari","doi":"10.1016/j.jrmge.2023.08.011","DOIUrl":"https://doi.org/10.1016/j.jrmge.2023.08.011","url":null,"abstract":"Traditional global sensitivity analysis (GSA) neglects the epistemic uncertainties associated with the probabilistic characteristics (i.e. type of distribution type and its parameters) of input rock properties emanating due to the small size of datasets while mapping the relative importance of properties to the model response. This paper proposes an augmented Bayesian multi-model inference (BMMI) coupled with GSA methodology (BMMI-GSA) to address this issue by estimating the imprecision in the moment-independent sensitivity indices of rock structures arising from the small size of input data. The methodology employs BMMI to quantify the epistemic uncertainties associated with model type and parameters of input properties. The estimated uncertainties are propagated in estimating imprecision in moment-independent Borgonovo's indices by employing a reweighting approach on candidate probabilistic models. The proposed methodology is showcased for a rock slope prone to stress-controlled failure in the Himalayan region of India. The proposed methodology was superior to the conventional GSA (neglects all epistemic uncertainties) and Bayesian coupled GSA (B-GSA) (neglects model uncertainty) due to its capability to incorporate the uncertainties in both model type and parameters of properties. Imprecise Borgonovo's indices estimated via proposed methodology provide the confidence intervals of the sensitivity indices instead of their fixed-point estimates, which makes the user more informed in the data collection efforts. Analyses performed with the varying sample sizes suggested that the uncertainties in sensitivity indices reduce significantly with the increasing sample sizes. The accurate importance ranking of properties was only possible via samples of large sizes. Further, the impact of the prior knowledge in terms of prior ranges and distributions was significant; hence, any related assumption should be made carefully.","PeriodicalId":54219,"journal":{"name":"Journal of Rock Mechanics and Geotechnical Engineering","volume":"43 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135565453","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}
Pub Date : 2023-11-01DOI: 10.1016/j.jrmge.2023.09.007
Lei Sun, Xuhai Tang, Kareem Ramzy Aboayanah, Qi Zhao, Quansheng Liu, Giovanni Grasselli
This paper presents the development of a coupled modeling approach to simulate cryogenic thermo-hydro-mechanical (THM) processes associated with a freezing medium, which is then implemented in the combined finite-discrete element method code (FDEM) for multi-physics simulation. The governing equations are deduced based on energy and mass conservation, and static equilibrium equations, considering water/ice phase change, where the strong couplings between multi-fields are supplemented by critical coupling parameters (e.g. unfrozen water content, permeability, and thermal conductivity). The proposed model is validated against laboratory and field experiments. Results show that the cryogenic THM model can well predict the evolution of strongly coupled processes observed in frozen media (e.g. heat transfer, water migration, and frost heave deformation), while also capturing, as emergent properties of the model, important phenomena (e.g. latent heat, cryogenic suction, ice expansion and distinct three-zone distribution) caused by water/ice phase change at laboratory and field scales, which are difficult to be all revealed by existing THM models. The novel modeling framework presents a gateway to further understanding and predicting the multi-physical coupling behavior of frozen media in cold regions.
{"title":"A coupled cryogenic thermo-hydro-mechanical model for frozen medium: Theory and implementation in FDEM","authors":"Lei Sun, Xuhai Tang, Kareem Ramzy Aboayanah, Qi Zhao, Quansheng Liu, Giovanni Grasselli","doi":"10.1016/j.jrmge.2023.09.007","DOIUrl":"https://doi.org/10.1016/j.jrmge.2023.09.007","url":null,"abstract":"This paper presents the development of a coupled modeling approach to simulate cryogenic thermo-hydro-mechanical (THM) processes associated with a freezing medium, which is then implemented in the combined finite-discrete element method code (FDEM) for multi-physics simulation. The governing equations are deduced based on energy and mass conservation, and static equilibrium equations, considering water/ice phase change, where the strong couplings between multi-fields are supplemented by critical coupling parameters (e.g. unfrozen water content, permeability, and thermal conductivity). The proposed model is validated against laboratory and field experiments. Results show that the cryogenic THM model can well predict the evolution of strongly coupled processes observed in frozen media (e.g. heat transfer, water migration, and frost heave deformation), while also capturing, as emergent properties of the model, important phenomena (e.g. latent heat, cryogenic suction, ice expansion and distinct three-zone distribution) caused by water/ice phase change at laboratory and field scales, which are difficult to be all revealed by existing THM models. The novel modeling framework presents a gateway to further understanding and predicting the multi-physical coupling behavior of frozen media in cold regions.","PeriodicalId":54219,"journal":{"name":"Journal of Rock Mechanics and Geotechnical Engineering","volume":"8 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135715365","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}
Pub Date : 2023-11-01DOI: 10.1016/j.jrmge.2023.09.006
Chengxin Feng, Marcos A. Valdebenito, Marcin Chwała, Kang Liao, Matteo Broggi, Michael Beer
Spatial variability of soil properties imposes a challenge for practical analysis and design in geotechnical engineering. The latter is particularly true for slope stability assessment, where the effects of uncertainty are synthesized in the so-called probability of failure. This probability quantifies the reliability of a slope and its numerical calculation is usually quite involved from a numerical viewpoint. In view of this issue, this paper proposes an approach for failure probability assessment based on Latinized partially stratified sampling and maximum entropy distribution with fractional moments. The spatial variability of geotechnical properties is represented by means of random fields and the Karhunen-Loève expansion. Then, failure probabilities are estimated employing maximum entropy distribution with fractional moments. The application of the proposed approach is examined with two examples: a case study of an undrained slope and a case study of a slope with cross-correlated random fields of strength parameters under a drained slope. The results show that the proposed approach has excellent accuracy and high efficiency, and it can be applied straightforwardly to similar geotechnical engineering problems.
{"title":"Efficient slope reliability analysis under soil spatial variability using maximum entropy distribution with fractional moments","authors":"Chengxin Feng, Marcos A. Valdebenito, Marcin Chwała, Kang Liao, Matteo Broggi, Michael Beer","doi":"10.1016/j.jrmge.2023.09.006","DOIUrl":"https://doi.org/10.1016/j.jrmge.2023.09.006","url":null,"abstract":"Spatial variability of soil properties imposes a challenge for practical analysis and design in geotechnical engineering. The latter is particularly true for slope stability assessment, where the effects of uncertainty are synthesized in the so-called probability of failure. This probability quantifies the reliability of a slope and its numerical calculation is usually quite involved from a numerical viewpoint. In view of this issue, this paper proposes an approach for failure probability assessment based on Latinized partially stratified sampling and maximum entropy distribution with fractional moments. The spatial variability of geotechnical properties is represented by means of random fields and the Karhunen-Loève expansion. Then, failure probabilities are estimated employing maximum entropy distribution with fractional moments. The application of the proposed approach is examined with two examples: a case study of an undrained slope and a case study of a slope with cross-correlated random fields of strength parameters under a drained slope. The results show that the proposed approach has excellent accuracy and high efficiency, and it can be applied straightforwardly to similar geotechnical engineering problems.","PeriodicalId":54219,"journal":{"name":"Journal of Rock Mechanics and Geotechnical Engineering","volume":"27 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135412593","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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