Pub Date : 2021-01-01DOI: 10.12989/GAE.2021.25.4.341
S. Chong
1D sand compression response to ko-loading experiences volume contraction from low to high effective stress regimes. Previous study suggested compressibility model with physically correct asymptotic void ratios at low and high stress levels and examined only for both remolded clays and natural clays. This study extends the validity of Enhanced Terzaghi model for different sand types complied from 1D compression data. The model involved with four parameters can adequately fit 1D sand compression data for a wide stress range. The low stress obtained from fitting parameters helps to identify the initial fabric conditions. In addition, strong correlation between compressibility and the void ratio at low stress facilitates determination of self-consistent fitting parameters. The computed tangent constrained modulus can capture monotonic stiffening effect induced by an increase in effective stress. The magnitude of tangent stiffness during large strain test should not be associated with small strain stiffness values. The use of a single continuous function to capture 1D stress-strain sand response to ko-loading can improve numerical efficiency and systematically quantify the yield stress instead of ad hoc methods.
{"title":"Investigation of 1D sand compression response using enhanced compressibility model","authors":"S. Chong","doi":"10.12989/GAE.2021.25.4.341","DOIUrl":"https://doi.org/10.12989/GAE.2021.25.4.341","url":null,"abstract":"1D sand compression response to ko-loading experiences volume contraction from low to high effective stress regimes. Previous study suggested compressibility model with physically correct asymptotic void ratios at low and high stress levels and examined only for both remolded clays and natural clays. This study extends the validity of Enhanced Terzaghi model for different sand types complied from 1D compression data. The model involved with four parameters can adequately fit 1D sand compression data for a wide stress range. The low stress obtained from fitting parameters helps to identify the initial fabric conditions. In addition, strong correlation between compressibility and the void ratio at low stress facilitates determination of self-consistent fitting parameters. The computed tangent constrained modulus can capture monotonic stiffening effect induced by an increase in effective stress. The magnitude of tangent stiffness during large strain test should not be associated with small strain stiffness values. The use of a single continuous function to capture 1D stress-strain sand response to ko-loading can improve numerical efficiency and systematically quantify the yield stress instead of ad hoc methods.","PeriodicalId":12602,"journal":{"name":"Geomechanics and Engineering","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66476540","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2021-01-01DOI: 10.12989/GAE.2021.25.4.267
I. Abbas
In this work, we compare the analytical solutions with the numerical solutions for photothermal interactions in semiconductor medium containing cylindrical cavity. This paper is devoted to a study of the photothermal interactions in semiconductor medium in the context of the coupled photo-thermal model. The basic equations are formulated in the domain of Laplace transform and the eigenvalue scheme are used to get the analytical solutions. The numerical solution is obtained by using the implicit finite difference method (IFDM). A comparison between the analytical solution and the numerical solutions are obtained. It is found that the implicit finite difference method (IFDM) is applicable, simple and efficient for such problems.
{"title":"A photo-thermal interaction in semi-conductor medium with cylindrical cavity by analytical and numerical methods","authors":"I. Abbas","doi":"10.12989/GAE.2021.25.4.267","DOIUrl":"https://doi.org/10.12989/GAE.2021.25.4.267","url":null,"abstract":"In this work, we compare the analytical solutions with the numerical solutions for photothermal interactions in semiconductor medium containing cylindrical cavity. This paper is devoted to a study of the photothermal interactions in semiconductor medium in the context of the coupled photo-thermal model. The basic equations are formulated in the domain of Laplace transform and the eigenvalue scheme are used to get the analytical solutions. The numerical solution is obtained by using the implicit finite difference method (IFDM). A comparison between the analytical solution and the numerical solutions are obtained. It is found that the implicit finite difference method (IFDM) is applicable, simple and efficient for such problems.","PeriodicalId":12602,"journal":{"name":"Geomechanics and Engineering","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66476677","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2021-01-01DOI: 10.12989/GAE.2021.26.3.215
W. Hong, Seongwon Hong
To investigate the settlement characteristics of drilled shaft socketed into igneous, metamorphic, or sedimentary rock, experimental results of the pile load tests were thoroughly collected in 20 different locations, clearly tabulated, and extensively compared with the standards for assessment of ultimate load. Total and elastic settlement patterns of drill shaft were completely dependent on the socketed pile length, the imposed load, the pile diameter, and the shear stress in bedrock, whereas residual settlement did not depend on the factors. It was also observed that the trends of total, residual, and elastic settlements were independent on bedrock types. Comparison between the experimental data and the standards shows that the total and residual settlements of large drilled shaft socketed in bedrock were too high to determine the ultimate load, and the reasonable amount of total or residual settlement measured from pile load test is proposed to assess the ultimate load capacity of drilled shaft socketed in bedrock.
{"title":"Assessment of ultimate load of drilled shaft socketed in rocks based on pile load tests","authors":"W. Hong, Seongwon Hong","doi":"10.12989/GAE.2021.26.3.215","DOIUrl":"https://doi.org/10.12989/GAE.2021.26.3.215","url":null,"abstract":"To investigate the settlement characteristics of drilled shaft socketed into igneous, metamorphic, or sedimentary rock, experimental results of the pile load tests were thoroughly collected in 20 different locations, clearly tabulated, and extensively compared with the standards for assessment of ultimate load. Total and elastic settlement patterns of drill shaft were completely dependent on the socketed pile length, the imposed load, the pile diameter, and the shear stress in bedrock, whereas residual settlement did not depend on the factors. It was also observed that the trends of total, residual, and elastic settlements were independent on bedrock types. Comparison between the experimental data and the standards shows that the total and residual settlements of large drilled shaft socketed in bedrock were too high to determine the ultimate load, and the reasonable amount of total or residual settlement measured from pile load test is proposed to assess the ultimate load capacity of drilled shaft socketed in bedrock.","PeriodicalId":12602,"journal":{"name":"Geomechanics and Engineering","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66478080","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2021-01-01DOI: 10.12989/GAE.2021.26.2.191
Jian Zhou, Xin-an Yang
The [BQ] method is a rock mass classification method to evaluate the quality of the rock mass and determine the construction parameters. This method is more empirical and cannot provide predictions for the deformation of tunnels after excavation. To predict the surrounding rock deformation of deep-buried tunnels by using the [BQ] method in China, first, data of 52 tunnels were collected and analyzed to determine the relationship between the grades of the surrounding rock, excavation method, burial depth, tunnel span, and surrounding rock deformation. Second, the equivalence of different surrounding rock grades to the range of geological strength index (GSI) scores were determined using methods, such as fitting GSI to another classification system RMR and RMR to BQ, and considering the correction factors of BQ values. This approach provides the basis for theoretical calculations based on the Hoek–Brown strength criterion. On the basis of the Hoek–Brown strength criterion, a theoretical approach to the deformation of surrounding rock under three failure models, namely, elastic–brittle–plastic, strain-softening, and elastic-perfectly-plastic, is presented when considering the installation time of primary support and the volumetric force of bolts. Finally, the theoretical approach is analyzed and compared with the measured data to verify its feasibility. Moreover, the effects of burial depth, grades of surrounding rock, support parameters, support time, and deformation allowance of the surrounding rock are analyzed. Analysis results can provide some guidance for the prediction of surrounding rock deformation of deep-buried tunnels in China.
{"title":"Deformation behavior analysis of tunnels opened in various rock mass grades conditions in China","authors":"Jian Zhou, Xin-an Yang","doi":"10.12989/GAE.2021.26.2.191","DOIUrl":"https://doi.org/10.12989/GAE.2021.26.2.191","url":null,"abstract":"The [BQ] method is a rock mass classification method to evaluate the quality of the rock mass and determine the construction parameters. This method is more empirical and cannot provide predictions for the deformation of tunnels after excavation. To predict the surrounding rock deformation of deep-buried tunnels by using the [BQ] method in China, first, data of 52 tunnels were collected and analyzed to determine the relationship between the grades of the surrounding rock, excavation method, burial depth, tunnel span, and surrounding rock deformation. Second, the equivalence of different surrounding rock grades to the range of geological strength index (GSI) scores were determined using methods, such as fitting GSI to another classification system RMR and RMR to BQ, and considering the correction factors of BQ values. This approach provides the basis for theoretical calculations based on the Hoek–Brown strength criterion. On the basis of the Hoek–Brown strength criterion, a theoretical approach to the deformation of surrounding rock under three failure models, namely, elastic–brittle–plastic, strain-softening, and elastic-perfectly-plastic, is presented when considering the installation time of primary support and the volumetric force of bolts. Finally, the theoretical approach is analyzed and compared with the measured data to verify its feasibility. Moreover, the effects of burial depth, grades of surrounding rock, support parameters, support time, and deformation allowance of the surrounding rock are analyzed. Analysis results can provide some guidance for the prediction of surrounding rock deformation of deep-buried tunnels in China.","PeriodicalId":12602,"journal":{"name":"Geomechanics and Engineering","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66478457","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2021-01-01DOI: 10.12989/GAE.2021.26.5.477
Xinshuai Shi, Yujing Jiang, H. Jing, Yuanchao Zhang, Yuan Gao, Z. Zhao, Q. Yin
The effect of heat treatment and the bedding orientation on the tensile properties, the central strain and failure patterns of bedded sandstone specimens were studied under Brazilian test conditions. The laboratory test results show that the tensile strength decreases with increasing bedding orientation at different temperatures, which indicates the bedded sandstone possesses prominent anisotropy in tensile strength. The anisotropy coefficient first increases and then decreases with the increasing temperature. For all temperatures, both V-strain and S-strain present a decreasing trend with increasing bedding orientation. However, for all bedding orientations, the S-strain first increases and then decreases, but V-strain continues to increase with increasing temperature. Furthermore, the failure patterns of the failed specimens are generally classified into three categories: central across the bedding planes (CF), fracture along the bedding planes (LA) and the mixed fracture patterns of the two. Finally, the evolution of the internal structure of the disk specimens after different heat treatments was investigated by SEM tests. The specimen profile looks smoother and denser at 400oC and 600oC, but at 800oC and 1000oC, the internal structure of the specimen is sharply deteriorated by thermal reactions.
{"title":"Effect of heat treatment and bedding orientation on the tensile properties of bedded sandstone","authors":"Xinshuai Shi, Yujing Jiang, H. Jing, Yuanchao Zhang, Yuan Gao, Z. Zhao, Q. Yin","doi":"10.12989/GAE.2021.26.5.477","DOIUrl":"https://doi.org/10.12989/GAE.2021.26.5.477","url":null,"abstract":"The effect of heat treatment and the bedding orientation on the tensile properties, the central strain and failure patterns of bedded sandstone specimens were studied under Brazilian test conditions. The laboratory test results show that the tensile strength decreases with increasing bedding orientation at different temperatures, which indicates the bedded sandstone possesses prominent anisotropy in tensile strength. The anisotropy coefficient first increases and then decreases with the increasing temperature. For all temperatures, both V-strain and S-strain present a decreasing trend with increasing bedding orientation. However, for all bedding orientations, the S-strain first increases and then decreases, but V-strain continues to increase with increasing temperature. Furthermore, the failure patterns of the failed specimens are generally classified into three categories: central across the bedding planes (CF), fracture along the bedding planes (LA) and the mixed fracture patterns of the two. Finally, the evolution of the internal structure of the disk specimens after different heat treatments was investigated by SEM tests. The specimen profile looks smoother and denser at 400oC and 600oC, but at 800oC and 1000oC, the internal structure of the specimen is sharply deteriorated by thermal reactions.","PeriodicalId":12602,"journal":{"name":"Geomechanics and Engineering","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66479657","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2021-01-01DOI: 10.12989/GAE.2021.27.2.179
Youngjin Son, T. Ko, Dongseop Lee, Jongmuk Won, I. Lee, Hangseok Choi
The artificial ground freezing technique has been widely adopted in tunnel construction in order to impede heavy water flow and to reinforce weak sections during excavation. While liquid nitrogen is one of common cryogenic refrigerants particularly for rapid freezing, it has a serious potential risk of suffocation due to an abrupt increase in nitrogen content in the atmosphere after being vaporized. This paper introduces a novel cryogenic refrigerant, liquid air, and addresses the applicability of it by performing a series of laboratory chamber experiments. The key parameters for the application of artificial freezing using liquid air in subsea tunnel construction are freezing time and energy consumption, which were evaluated and discussed in this paper. The comparative study of these parameters between the use of liquid air and liquid nitrogen demonstrates that liquid air with no risk of suffocation can be a potential substitute for liquid nitrogen delivering the equivalent performance. In addition, the theoretical model was adopted to evaluate the chamber experiments in an effort to estimate the freezing time and the energy consumption ratio (energy consumption for maintaining the frozen state to the energy consumption for freezing soil specimens).
{"title":"Applicability of liquid air as novel cryogenic refrigerant for subsea tunnelling construction","authors":"Youngjin Son, T. Ko, Dongseop Lee, Jongmuk Won, I. Lee, Hangseok Choi","doi":"10.12989/GAE.2021.27.2.179","DOIUrl":"https://doi.org/10.12989/GAE.2021.27.2.179","url":null,"abstract":"The artificial ground freezing technique has been widely adopted in tunnel construction in order to impede heavy water flow and to reinforce weak sections during excavation. While liquid nitrogen is one of common cryogenic refrigerants particularly for rapid freezing, it has a serious potential risk of suffocation due to an abrupt increase in nitrogen content in the atmosphere after being vaporized. This paper introduces a novel cryogenic refrigerant, liquid air, and addresses the applicability of it by performing a series of laboratory chamber experiments. The key parameters for the application of artificial freezing using liquid air in subsea tunnel construction are freezing time and energy consumption, which were evaluated and discussed in this paper. The comparative study of these parameters between the use of liquid air and liquid nitrogen demonstrates that liquid air with no risk of suffocation can be a potential substitute for liquid nitrogen delivering the equivalent performance. In addition, the theoretical model was adopted to evaluate the chamber experiments in an effort to estimate the freezing time and the energy consumption ratio (energy consumption for maintaining the frozen state to the energy consumption for freezing soil specimens).","PeriodicalId":12602,"journal":{"name":"Geomechanics and Engineering","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66481422","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2021-01-01DOI: 10.12989/GAE.2021.24.2.179
Bingquan Chen, Zhiguo Xia, Yadong Xu, Shuai Liu, Xingzong Liu
In this study, the strength and failure mechanism of red sandstones with combined defects were investigated by uniaxial compression tests on red sandstones with different crack angles using two-dimensional particle flow code numerical software, and their mechanical parameters and failure process were studied and analyzed. The results showed that the mechanical characteristics such as peak strength, peak strain, and elastic modulus of the samples with prefabricated combined defects were significantly inferior than those of the intact samples. With increasing crack angle from 15° to 60°, the weakening area of cracks increased, elastic modulus, peak strength, and peak strain gradually reduced, the total number of cracks increased, and more strain energy was released. In addition, the samples underwent initial brittle failure to plastic failure stage, and the failure form was more significant, leading to peeling phenomenon. However, with increasing crack angle from 75° to 90°, the crack–hole combination shared the stress concentration at the tip of the crack–crack combination, resulted in a gradual increase in elastic modulus, peak strain and peak strength, but a decrease in the number of total cracks, the release of strain energy reduced, the plastic failure state weakened, and the spalling phenomenon slowed down. On this basis, the samples with 30° and 45°crack-crack combination were selected for further experimental investigation. Through comparative analysis between the experimental and simulation results, the failure strength and final failure mode with cracks propagation of samples were found to be relatively similar.
{"title":"Failure characteristics and mechanical mechanism of study on red sandstone with combined defects","authors":"Bingquan Chen, Zhiguo Xia, Yadong Xu, Shuai Liu, Xingzong Liu","doi":"10.12989/GAE.2021.24.2.179","DOIUrl":"https://doi.org/10.12989/GAE.2021.24.2.179","url":null,"abstract":"In this study, the strength and failure mechanism of red sandstones with combined defects were investigated by uniaxial compression tests on red sandstones with different crack angles using two-dimensional particle flow code numerical software, and their mechanical parameters and failure process were studied and analyzed. The results showed that the mechanical characteristics such as peak strength, peak strain, and elastic modulus of the samples with prefabricated combined defects were significantly inferior than those of the intact samples. With increasing crack angle from 15° to 60°, the weakening area of cracks increased, elastic modulus, peak strength, and peak strain gradually reduced, the total number of cracks increased, and more strain energy was released. In addition, the samples underwent initial brittle failure to plastic failure stage, and the failure form was more significant, leading to peeling phenomenon. However, with increasing crack angle from 75° to 90°, the crack–hole combination shared the stress concentration at the tip of the crack–crack combination, resulted in a gradual increase in elastic modulus, peak strain and peak strength, but a decrease in the number of total cracks, the release of strain energy reduced, the plastic failure state weakened, and the spalling phenomenon slowed down. On this basis, the samples with 30° and 45°crack-crack combination were selected for further experimental investigation. Through comparative analysis between the experimental and simulation results, the failure strength and final failure mode with cracks propagation of samples were found to be relatively similar.","PeriodicalId":12602,"journal":{"name":"Geomechanics and Engineering","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66472151","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pre-drainage of groundwater in the roof aquifer by boreholes is the main method for prevention of roof water disaster, and the drop in the water level during the drainage leads to the variation of the local stress in the overlying strata. Based on a multitude of boreholes for groundwater drainage from aquifer above the 1303 mining face of Longyun Coal Mine, theoretical analysis and numerical simulation are used to investigate the local stress variation in the process of borehole drainage. The results show that due to the drop in the water level of the roof aquifer during the drainage, the stress around the borehole gradually evolved. From the center of the borehole to the outside, a stress-relaxed zone, a stress-elevated zone, and a stress-recovered zone are sequentially formed. Along with the expansion of drainage influence, the stress peak in the stress-elevated zone also moves to the outside. When the radius of influence develops to the maximum, the stress peak position no longer moves outward. When the coal mining face advances to the drainage influence range, the abutment pressure in front of the mining face is superimposed with the high local stress around the borehole, which increases the risk of stress concentration. The present study provides a reference for the stress concentration caused by borehole drainage, which can be potentially utilized in the optimal arrangement of drainage boreholes in underground mining.
{"title":"Effects of the borehole drainage for roof aquifer on local stress in underground mining","authors":"Jianli Shao, Qi Zhang, Zhang Wenquan, Zaiyong Wang, Xintao Wu","doi":"10.12989/GAE.2021.24.5.479","DOIUrl":"https://doi.org/10.12989/GAE.2021.24.5.479","url":null,"abstract":"Pre-drainage of groundwater in the roof aquifer by boreholes is the main method for prevention of roof water disaster, and the drop in the water level during the drainage leads to the variation of the local stress in the overlying strata. Based on a multitude of boreholes for groundwater drainage from aquifer above the 1303 mining face of Longyun Coal Mine, theoretical analysis and numerical simulation are used to investigate the local stress variation in the process of borehole drainage. The results show that due to the drop in the water level of the roof aquifer during the drainage, the stress around the borehole gradually evolved. From the center of the borehole to the outside, a stress-relaxed zone, a stress-elevated zone, and a stress-recovered zone are sequentially formed. Along with the expansion of drainage influence, the stress peak in the stress-elevated zone also moves to the outside. When the radius of influence develops to the maximum, the stress peak position no longer moves outward. When the coal mining face advances to the drainage influence range, the abutment pressure in front of the mining face is superimposed with the high local stress around the borehole, which increases the risk of stress concentration. The present study provides a reference for the stress concentration caused by borehole drainage, which can be potentially utilized in the optimal arrangement of drainage boreholes in underground mining.","PeriodicalId":12602,"journal":{"name":"Geomechanics and Engineering","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66475222","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2021-01-01DOI: 10.12989/GAE.2021.24.6.505
Mohammad Zaid
The present paper has been carried out to understand the effects of impact loading on the rock tunnels, constructed in different region corresponding to varying unconfined compressive strength (UCS), through finite element method. The UCS of rockmass has substantial role in the stability of rock tunnels under impact loading condition due to falling rocks or other objects. In the present study, Dolomite, Shale, Sandstone, Granite, Basalt, and Quartzite rocks have been taken into consideration for understanding of the effect of UCS that vary from 2.85 MPa to 207.03 MPa. The Mohr-Coulomb constitutive model has been considered in the present study for the nonlinear elastoplastic analysis for all the rocks surrounding the tunnel opening. The geometry and boundary conditions of the model remains constant throughout the analysis and missile has 100 kg of weight. The general hard contact has been assigned to incorporate the interaction between different parts of the model. The present study focuses on studying the deformations in the rock tunnel caused by impacting load due to missile for tunnels having different concrete grade, and steel grade. The broader range of rock strength depicts the strong relationship between the UCS of rock and the extent of damage produced under different impact loading conditions. The energy released during an impact loading simulation shows the variation of safety and serviceability of the rock tunnel.
{"title":"Dynamic stability analysis of rock tunnels subjected to impact loading with varying UCS","authors":"Mohammad Zaid","doi":"10.12989/GAE.2021.24.6.505","DOIUrl":"https://doi.org/10.12989/GAE.2021.24.6.505","url":null,"abstract":"The present paper has been carried out to understand the effects of impact loading on the rock tunnels, constructed in different region corresponding to varying unconfined compressive strength (UCS), through finite element method. The UCS of rockmass has substantial role in the stability of rock tunnels under impact loading condition due to falling rocks or other objects. In the present study, Dolomite, Shale, Sandstone, Granite, Basalt, and Quartzite rocks have been taken into consideration for understanding of the effect of UCS that vary from 2.85 MPa to 207.03 MPa. The Mohr-Coulomb constitutive model has been considered in the present study for the nonlinear elastoplastic analysis for all the rocks surrounding the tunnel opening. The geometry and boundary conditions of the model remains constant throughout the analysis and missile has 100 kg of weight. The general hard contact has been assigned to incorporate the interaction between different parts of the model. The present study focuses on studying the deformations in the rock tunnel caused by impacting load due to missile for tunnels having different concrete grade, and steel grade. The broader range of rock strength depicts the strong relationship between the UCS of rock and the extent of damage produced under different impact loading conditions. The energy released during an impact loading simulation shows the variation of safety and serviceability of the rock tunnel.","PeriodicalId":12602,"journal":{"name":"Geomechanics and Engineering","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66475271","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2021-01-01DOI: 10.12989/GAE.2021.24.6.531
Garam Kim, Incheol Kim, T. Yun, Junhwan Lee
Freezing and thawing of pore water within backfill can affect the stability of retaining wall as the phase change of pore water causes changes in the mechanical characteristics of backfill material. In this study, the effects of freezing and thawing on the mechanical performance of retaining wall with granular backfill were investigated for various temperature and groundwater level (GWL) conditions. The thermal and mechanical finite element analyses were performed by assigning the coefficient of lateral earth pressure according to phase change of soil for at-rest, active and passive stress states. For the at-rest condition, the mobilized lateral stress and overturning moment changed markedly during freezing and thawing. Active-state displacements for the thawed condition were larger than for the unfrozen condition whereas the effect of freezing and thawing was small for the passive condition. GWL affected significantly the lateral force and overturning moment (Mo) acting on the wall during freezing and thawing, indicating that the reduction of safety margin and wall collapse due to freezing and thawing can occur in sudden, unexpected patterns. The beneficial effect of an insulation layer between the retaining wall and the backfill in reducing the heat conduction from the wall face was also investigated and presented.
{"title":"Effects of freezing and thawing on retaining wall with changes in groundwater level","authors":"Garam Kim, Incheol Kim, T. Yun, Junhwan Lee","doi":"10.12989/GAE.2021.24.6.531","DOIUrl":"https://doi.org/10.12989/GAE.2021.24.6.531","url":null,"abstract":"Freezing and thawing of pore water within backfill can affect the stability of retaining wall as the phase change of pore water causes changes in the mechanical characteristics of backfill material. In this study, the effects of freezing and thawing on the mechanical performance of retaining wall with granular backfill were investigated for various temperature and groundwater level (GWL) conditions. The thermal and mechanical finite element analyses were performed by assigning the coefficient of lateral earth pressure according to phase change of soil for at-rest, active and passive stress states. For the at-rest condition, the mobilized lateral stress and overturning moment changed markedly during freezing and thawing. Active-state displacements for the thawed condition were larger than for the unfrozen condition whereas the effect of freezing and thawing was small for the passive condition. GWL affected significantly the lateral force and overturning moment (Mo) acting on the wall during freezing and thawing, indicating that the reduction of safety margin and wall collapse due to freezing and thawing can occur in sudden, unexpected patterns. The beneficial effect of an insulation layer between the retaining wall and the backfill in reducing the heat conduction from the wall face was also investigated and presented.","PeriodicalId":12602,"journal":{"name":"Geomechanics and Engineering","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66475480","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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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