Pub Date : 2021-01-01DOI: 10.12989/GAE.2021.24.6.589
A. Ardakani, A. Namaei
The present study evaluates geocell reinforced slope behavior. A three dimensional analysis is carried out to simulate soil and geocell elastoplastic behavior using the finite difference software FLAC3D. In order to investigate the geocell reinforcement effect, the geocell aperture size, thickness, geocell placement condition and soil compaction had been considered as variable parameters. Moreover, a comparison is evaluated between geocell reinforcing system and conventional planar reinforcement. The obtained results showed that the pocket size, thickness and soil compaction have considerable influence on the geocell reinforcement slope performance. Moreover, it was found that the critical sliding surface was bounded by the first geocell reinforcement and the slope stability increases, by increasing the vertical space between geocell layers. In addition, the comparison between geocell and geogrid reinforcement indicates the efficiency of using cellular honeycomb geosynthetic reinforcement.
{"title":"Numerical investigation of geocell reinforced slopes behaviorby considering geocell geometry effect","authors":"A. Ardakani, A. Namaei","doi":"10.12989/GAE.2021.24.6.589","DOIUrl":"https://doi.org/10.12989/GAE.2021.24.6.589","url":null,"abstract":"The present study evaluates geocell reinforced slope behavior. A three dimensional analysis is carried out to simulate soil and geocell elastoplastic behavior using the finite difference software FLAC3D. In order to investigate the geocell reinforcement effect, the geocell aperture size, thickness, geocell placement condition and soil compaction had been considered as variable parameters. Moreover, a comparison is evaluated between geocell reinforcing system and conventional planar reinforcement. The obtained results showed that the pocket size, thickness and soil compaction have considerable influence on the geocell reinforcement slope performance. Moreover, it was found that the critical sliding surface was bounded by the first geocell reinforcement and the slope stability increases, by increasing the vertical space between geocell layers. In addition, the comparison between geocell and geogrid reinforcement indicates the efficiency of using cellular honeycomb geosynthetic reinforcement.","PeriodicalId":12602,"journal":{"name":"Geomechanics and Engineering","volume":"24 1","pages":"589"},"PeriodicalIF":3.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66475866","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.2021.25.3.245
Emel Çakar, Y. Yukselen-Aksoy
The present study investigated the ageing effect on compressibility, permeability and shear strength behavior of kaolin and bentonite samples in the presence of NaCl and CaCl2 solutions. The compressibility, permeability and shear strength parameters were determined on the 60, 190, and 250 days cured samples. The results have shown that, the kaolin sample becomes more compressible in the presence Ca2+ ions with ageing. Generally, the normalized compression index values of bentonite samples increased at the end of 60 days and 250 days curing time periods. The normalized permeability value of kaolin decreased by ageing in the presence of Na+ ions almost twofold. The permeability values of bentonite increased both in NaCl and CaCl2 solutions during ageing. In the presence of Na+ ions kaolin had higher max. shear stress value than Ca2+ ions. When the max. shear stress values of 0, 60 and 190 days samples were compared, it was seen that NaCl solution had no significant effect on the shear strength of kaolin sample. However, the shear strength of kaolin increased in the CaCl2 solution during ageing. In the presence of Ca2+ ions the max. shear stress value of bentonite was higher. The results of this study have shown that ageing has significant effects on the compressibility, permeability and shear strength of kaolinitic and bentonitic clayey soils.
{"title":"Ageing effect on compressibility, permeability and shear strength of clayey soils exposed to salt solutions","authors":"Emel Çakar, Y. Yukselen-Aksoy","doi":"10.12989/GAE.2021.25.3.245","DOIUrl":"https://doi.org/10.12989/GAE.2021.25.3.245","url":null,"abstract":"The present study investigated the ageing effect on compressibility, permeability and shear strength behavior of kaolin and bentonite samples in the presence of NaCl and CaCl2 solutions. The compressibility, permeability and shear strength parameters were determined on the 60, 190, and 250 days cured samples. The results have shown that, the kaolin sample becomes more compressible in the presence Ca2+ ions with ageing. Generally, the normalized compression index values of bentonite samples increased at the end of 60 days and 250 days curing time periods. The normalized permeability value of kaolin decreased by ageing in the presence of Na+ ions almost twofold. The permeability values of bentonite increased both in NaCl and CaCl2 solutions during ageing. In the presence of Na+ ions kaolin had higher max. shear stress value than Ca2+ ions. When the max. shear stress values of 0, 60 and 190 days samples were compared, it was seen that NaCl solution had no significant effect on the shear strength of kaolin sample. However, the shear strength of kaolin increased in the CaCl2 solution during ageing. In the presence of Ca2+ ions the max. shear stress value of bentonite was higher. The results of this study have shown that ageing has significant effects on the compressibility, permeability and shear strength of kaolinitic and bentonitic clayey soils.","PeriodicalId":12602,"journal":{"name":"Geomechanics and Engineering","volume":"25 1","pages":"245"},"PeriodicalIF":3.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66476515","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.2021.26.4.357
W. Wang, Bin Zhao, Aiyu Hu, J. Shang
Under compression, the flaws in soils will not only weaken the mechanical properties of soils, but also affect the strain localization of soils. In order to study the influence of flaws on the behavior of soils under compression, the uniaxial compression tests of clays with different inclination and position fissures were carried out, and the two-dimensional numerical analysis was also discussed based on the damage plasticity model. Analyzing the results of the uniaxial compression test and simulation of the intact and fissured clays, the following conclusions can be drawn: (1) The 60-degree fissure located on the upper position of the right edge of the clay has the greatest influence on the failure form and damage energy of clays, which can reduce the compression strength by 30% compared with that of the intact clay. (2) The numerical method based on the damage plasticity model can basically simulate the compression behavior of clays containing a pre-existing fissure and reproduce the failure characteristics of clays. (3) The preset fissure has obvious influence on the evolution of maximum principal stress in the area with serious damage, but less on the shear stress. And in the area with slight damage, the effect on the maximum principal stress and shear stress is very weak.
{"title":"Influence of a preset fissure on clay behavior under uniaxial compression","authors":"W. Wang, Bin Zhao, Aiyu Hu, J. Shang","doi":"10.12989/GAE.2021.26.4.357","DOIUrl":"https://doi.org/10.12989/GAE.2021.26.4.357","url":null,"abstract":"Under compression, the flaws in soils will not only weaken the mechanical properties of soils, but also affect the strain localization of soils. In order to study the influence of flaws on the behavior of soils under compression, the uniaxial compression tests of clays with different inclination and position fissures were carried out, and the two-dimensional numerical analysis was also discussed based on the damage plasticity model. Analyzing the results of the uniaxial compression test and simulation of the intact and fissured clays, the following conclusions can be drawn: (1) The 60-degree fissure located on the upper position of the right edge of the clay has the greatest influence on the failure form and damage energy of clays, which can reduce the compression strength by 30% compared with that of the intact clay. (2) The numerical method based on the damage plasticity model can basically simulate the compression behavior of clays containing a pre-existing fissure and reproduce the failure characteristics of clays. (3) The preset fissure has obvious influence on the evolution of maximum principal stress in the area with serious damage, but less on the shear stress. And in the area with slight damage, the effect on the maximum principal stress and shear stress is very weak.","PeriodicalId":12602,"journal":{"name":"Geomechanics and Engineering","volume":"26 1","pages":"357"},"PeriodicalIF":3.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66479288","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.2021.26.3.261
Mi-Jeong Seo, Kyungsoo Han, Jongbae Park, Kyeong-han Jeong, Jong Sub Lee
The objective of this study is to investigate the effects of incorporating inclined base plates on the end bearing capacities of embedded piles by conducting dynamic pile tests and static load tests. Two types of embedded piles were prepared – conventional piles with a 50-cm-diameter flat base plate and piles with a 56-cm-diameter inclined base plate. The dynamic pile tests were conducted during pile construction, and the static load tests were conducted after curing the cement paste to investigate the end bearing capacities of the test piles. Test results indicate that the base resistances of piles with inclined base plates are greater than those of conventional piles and that the base resistances increase with an increase in the inclination angle. The increased projected area, increased contact area, extended rupture surface, and enhanced slime discharge due to the inclined base plate may result in an increase in the end bearing capacity of the pile. This study demonstrates that the end bearing capacities of the embedded piles may be maximized by incorporating inclined plates to the pile base. Thus, the pile with the inclined base plate may be effectively used for the construction of embedded piles.
{"title":"End bearing capacity of embedded pile with inclined base plate:Field dynamic and static tests","authors":"Mi-Jeong Seo, Kyungsoo Han, Jongbae Park, Kyeong-han Jeong, Jong Sub Lee","doi":"10.12989/GAE.2021.26.3.261","DOIUrl":"https://doi.org/10.12989/GAE.2021.26.3.261","url":null,"abstract":"The objective of this study is to investigate the effects of incorporating inclined base plates on the end bearing capacities of embedded piles by conducting dynamic pile tests and static load tests. Two types of embedded piles were prepared – conventional piles with a 50-cm-diameter flat base plate and piles with a 56-cm-diameter inclined base plate. The dynamic pile tests were conducted during pile construction, and the static load tests were conducted after curing the cement paste to investigate the end bearing capacities of the test piles. Test results indicate that the base resistances of piles with inclined base plates are greater than those of conventional piles and that the base resistances increase with an increase in the inclination angle. The increased projected area, increased contact area, extended rupture surface, and enhanced slime discharge due to the inclined base plate may result in an increase in the end bearing capacity of the pile. This study demonstrates that the end bearing capacities of the embedded piles may be maximized by incorporating inclined plates to the pile base. Thus, the pile with the inclined base plate may be effectively used for the construction of embedded piles.","PeriodicalId":12602,"journal":{"name":"Geomechanics and Engineering","volume":"26 1","pages":"261"},"PeriodicalIF":3.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66478363","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.2021.24.2.115
I. Bozbey, M. K. Kelesoglu, S. Oztoprak, Muhammet Komut, Senol Comez, T. Ozturk, Aykan Mert, K. Ocal
{"title":"Effects of soaking on a lime stabilized clay and implications for pavement design","authors":"I. Bozbey, M. K. Kelesoglu, S. Oztoprak, Muhammet Komut, Senol Comez, T. Ozturk, Aykan Mert, K. Ocal","doi":"10.12989/GAE.2021.24.2.115","DOIUrl":"https://doi.org/10.12989/GAE.2021.24.2.115","url":null,"abstract":"","PeriodicalId":12602,"journal":{"name":"Geomechanics and Engineering","volume":"24 1","pages":"115"},"PeriodicalIF":3.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66472032","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.2021.24.2.167
Suozhu Fei, Xiaohui Tan, W. Gong, Xiaole Dong, F. Zha, Long Xu
Spatial variability is an inherent uncertainty of soil properties. Current reliability analyses generally incorporate random field theory and Monte Carlo simulation (MCS) when dealing with spatial variability, in which the computational efficiency is a significant challenge. This paper proposes a KL-FORM algorithm to improve the computational efficiency. In the proposed KL-FORM, Karhunen-Loeve (KL) expansion is used for discretizing random fields, and first-order reliability method (FORM) is employed for reliability analysis. The KL expansion and FORM can be used in conjunction, through adopting independent standard normal variables in the discretization of KL expansion as the basic variables in the FORM. To illustrate the effectiveness of this KL-FORM, it is applied to a case study of a strip footing in spatially variable unsaturated soil under rainfall, in which the bearing capacity of the footing is computed by numerical simulation. This case study shows that the KL-FORM is accurate and efficient. The parametric analyses suggest that ignoring the spatial variability of the soil may lead to an underestimation of the reliability index of the footing.
{"title":"Reliability analysis of strip footing under rainfall using KL-FORM","authors":"Suozhu Fei, Xiaohui Tan, W. Gong, Xiaole Dong, F. Zha, Long Xu","doi":"10.12989/GAE.2021.24.2.167","DOIUrl":"https://doi.org/10.12989/GAE.2021.24.2.167","url":null,"abstract":"Spatial variability is an inherent uncertainty of soil properties. Current reliability analyses generally incorporate random field theory and Monte Carlo simulation (MCS) when dealing with spatial variability, in which the computational efficiency is a significant challenge. This paper proposes a KL-FORM algorithm to improve the computational efficiency. In the proposed KL-FORM, Karhunen-Loeve (KL) expansion is used for discretizing random fields, and first-order reliability method (FORM) is employed for reliability analysis. The KL expansion and FORM can be used in conjunction, through adopting independent standard normal variables in the discretization of KL expansion as the basic variables in the FORM. To illustrate the effectiveness of this KL-FORM, it is applied to a case study of a strip footing in spatially variable unsaturated soil under rainfall, in which the bearing capacity of the footing is computed by numerical simulation. This case study shows that the KL-FORM is accurate and efficient. The parametric analyses suggest that ignoring the spatial variability of the soil may lead to an underestimation of the reliability index of the footing.","PeriodicalId":12602,"journal":{"name":"Geomechanics and Engineering","volume":"24 1","pages":"167"},"PeriodicalIF":3.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66472134","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.2021.24.4.307
R. Galindo, Jose Andres, A. Lara, Bin Xu, Z. Cao, Yuanqiang Cai
In an earlier publication (Serrano et al. 2014), the theoretical basis for evaluating the shear strength in rock joints was presented and used to derive an equation that governs the relationship between tangential and normal stresses on the joint during slippage between the joint faces. In this paper, the theoretical equation is applied to two non-linear failure criteria by using non-associated flow laws, including the modified Hoek and Brown and modified Mohr-Coulomb equations. The theoretical model considers the geometric dilatancy, the instantaneous friction angle, and a parameter that considers joint surface roughness as dependent variables. This model uses a similar equation structure to the empirical law that was proposed by Barton in 1973. However, a good correlation with the empirical values and, therefore, Barton's equation is necessary to incorporate a non-associated flow law that governs breakage processes in rock masses and becomes more significant in highly fractured media, which can be induced in a rock joint. A linear law of dilatancy is used to assess the importance of the non-associated flow to obtain very close values for different roughness states, so the best results are obtained for null material dilatancy, which considers significant changes that correspond to soft rock masses or altered zones of weakness.
在早期的一篇论文(Serrano et al. 2014)中，提出了评估岩石节理抗剪强度的理论基础，并用于推导出一个方程，该方程用于控制节理面之间滑动时节理上的切向应力和法向应力之间的关系。本文采用非关联流动规律将理论方程应用于两种非线性失效判据，包括修正的Hoek和Brown方程和修正的Mohr-Coulomb方程。该理论模型考虑了几何剪胀、瞬时摩擦角和以节理表面粗糙度为因变量的参数。该模型使用了与巴顿在1973年提出的经验法则相似的方程结构。然而，与经验值的良好相关性，因此，巴顿方程是必要的，以纳入一个非关联的流动规律，控制岩体中的破坏过程，在高度断裂的介质中变得更加重要，这可以在岩石节理中引起。利用剪胀率的线性规律来评估非关联流动的重要性，以获得不同粗糙度状态下非常接近的值，因此零材料剪胀率得到了最好的结果，它考虑了对应于软岩体或改变的软弱带的显著变化。
{"title":"Theoretical model for the shear strength of rock discontinuities with non-associated flow laws","authors":"R. Galindo, Jose Andres, A. Lara, Bin Xu, Z. Cao, Yuanqiang Cai","doi":"10.12989/GAE.2021.24.4.307","DOIUrl":"https://doi.org/10.12989/GAE.2021.24.4.307","url":null,"abstract":"In an earlier publication (Serrano et al. 2014), the theoretical basis for evaluating the shear strength in rock joints was presented and used to derive an equation that governs the relationship between tangential and normal stresses on the joint during slippage between the joint faces. In this paper, the theoretical equation is applied to two non-linear failure criteria by using non-associated flow laws, including the modified Hoek and Brown and modified Mohr-Coulomb equations. The theoretical model considers the geometric dilatancy, the instantaneous friction angle, and a parameter that considers joint surface roughness as dependent variables. This model uses a similar equation structure to the empirical law that was proposed by Barton in 1973. However, a good correlation with the empirical values and, therefore, Barton's equation is necessary to incorporate a non-associated flow law that governs breakage processes in rock masses and becomes more significant in highly fractured media, which can be induced in a rock joint. A linear law of dilatancy is used to assess the importance of the non-associated flow to obtain very close values for different roughness states, so the best results are obtained for null material dilatancy, which considers significant changes that correspond to soft rock masses or altered zones of weakness.","PeriodicalId":12602,"journal":{"name":"Geomechanics and Engineering","volume":"24 1","pages":"307"},"PeriodicalIF":3.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66472628","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.2021.24.5.457
S. Seo, H. Lim, M. Chung
In this study, the pull-out behavior of a tunnel-type anchorage for suspension bridges was investigated using experimental tests and image processing analyses. The study focused on evaluating the initial failure behavior and failure mode of the tunnel-type anchorage. In order to evaluate the failure mode of tunnel-type anchorage, a series of scaled model tests were conducted based on the prototype anchorage of the Ulsan Grand Bridge. In the model tests, the anchorage body and surrounding rocks were fabricated using a gypsum mixture. The pull-out behavior was investigated under plane strain conditions. The results of the model tests demonstrate that the tunnel-type anchorage underwent a wedge-shaped failure. In addition, the failure mode changed according to the differences in the physical properties of the surrounding rock and the anchorage body and the size of the anchor plate. The size of the anchor plate was found to be an important parameter that determines the failure mode. However, the difference in physical properties between the surrounding rock and the anchorage body did not affect its size. In addition, this study analyzed the initial failure behavior of the tunnel-type anchorage through image analysis and confirmed that the failure was sequentially transferred from the inside of the tunnel to the surrounding rock according to the image analysis. The reasonable failure mode for the design of the tunnel-type anchorage should be wedge-type rather than pull-out type.
{"title":"Evaluation of failure mode of tunnel-type anchorage for a suspension bridge via scaled model tests and image processing","authors":"S. Seo, H. Lim, M. Chung","doi":"10.12989/GAE.2021.24.5.457","DOIUrl":"https://doi.org/10.12989/GAE.2021.24.5.457","url":null,"abstract":"In this study, the pull-out behavior of a tunnel-type anchorage for suspension bridges was investigated using experimental tests and image processing analyses. The study focused on evaluating the initial failure behavior and failure mode of the tunnel-type anchorage. In order to evaluate the failure mode of tunnel-type anchorage, a series of scaled model tests were conducted based on the prototype anchorage of the Ulsan Grand Bridge. In the model tests, the anchorage body and surrounding rocks were fabricated using a gypsum mixture. The pull-out behavior was investigated under plane strain conditions. The results of the model tests demonstrate that the tunnel-type anchorage underwent a wedge-shaped failure. In addition, the failure mode changed according to the differences in the physical properties of the surrounding rock and the anchorage body and the size of the anchor plate. The size of the anchor plate was found to be an important parameter that determines the failure mode. However, the difference in physical properties between the surrounding rock and the anchorage body did not affect its size. In addition, this study analyzed the initial failure behavior of the tunnel-type anchorage through image analysis and confirmed that the failure was sequentially transferred from the inside of the tunnel to the surrounding rock according to the image analysis. The reasonable failure mode for the design of the tunnel-type anchorage should be wedge-type rather than pull-out type.","PeriodicalId":12602,"journal":{"name":"Geomechanics and Engineering","volume":"24 1","pages":"457"},"PeriodicalIF":3.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66475090","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.2021.24.5.419
Ye-xia Guo, W. Ni, Haisong Liu
Investigation on the compressibility and shear strength of compacted loess is of great importance for the design and operation of engineering infrastructures in filling area. In this study, the mechanical behaviors of Yan'an compacted loess are investigated at various dry densities and water contents by conducting one dimensional compression and direct shear tests. And the elastic compressibility, plastic compressibility, yield stress and strength are obtained from the experiments. Results show that when water content increases, plastic compressibility parameter increases, but yield stress decreases. However, the increase of dry density leads to a decrease in plastic compressibility parameter but an increase in yield stress. In addition, elastic compressibility parameter is found to be a constant which is irrelevant to water content and dry density. As for strength, cohesion and internal friction angle is directly proportional to dry density, but inversely proportional to water content. Moreover, the mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM) tests were also performed to observe the pore size distribution and microstructure of the specimens. Finally, by using results of MIP and SEM tests, the compressibility and strength behaviours of Yan'an compacted loess are explained from the perspective of pore-size distribution and microstructure.
{"title":"Effects of dry density and water content on compressibility and shear strength of loess","authors":"Ye-xia Guo, W. Ni, Haisong Liu","doi":"10.12989/GAE.2021.24.5.419","DOIUrl":"https://doi.org/10.12989/GAE.2021.24.5.419","url":null,"abstract":"Investigation on the compressibility and shear strength of compacted loess is of great importance for the design and operation of engineering infrastructures in filling area. In this study, the mechanical behaviors of Yan'an compacted loess are investigated at various dry densities and water contents by conducting one dimensional compression and direct shear tests. And the elastic compressibility, plastic compressibility, yield stress and strength are obtained from the experiments. Results show that when water content increases, plastic compressibility parameter increases, but yield stress decreases. However, the increase of dry density leads to a decrease in plastic compressibility parameter but an increase in yield stress. In addition, elastic compressibility parameter is found to be a constant which is irrelevant to water content and dry density. As for strength, cohesion and internal friction angle is directly proportional to dry density, but inversely proportional to water content. Moreover, the mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM) tests were also performed to observe the pore size distribution and microstructure of the specimens. Finally, by using results of MIP and SEM tests, the compressibility and strength behaviours of Yan'an compacted loess are explained from the perspective of pore-size distribution and microstructure.","PeriodicalId":12602,"journal":{"name":"Geomechanics and Engineering","volume":"6 1","pages":"419"},"PeriodicalIF":3.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66475363","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.2021.25.1.017
Bin Li, Yong Fu, Yi Hong, Zijun Cao
This paper develops a convenient approach for deterministic and probabilistic evaluations of tunnel face stability using support vector machine classifiers. The proposed method is comprised of two major steps, i.e., construction of the training dataset and determination of instance-based classifiers. In step one, the orthogonal design is utilized to produce representative samples after the ranges and levels of the factors that influence tunnel face stability are specified. The training dataset is then labeled by two-dimensional strength reduction analyses embedded within OptumG2. For any unknown instance, the second step applies the training dataset for classification, which is achieved by an ad hoc Python program. The classification of unknown samples starts with selection of instance-based training samples using the k-nearest neighbors algorithm, followed by the construction of an instance-based SVM-KNN classifier. It eventually provides labels of the unknown instances, avoiding calculate its corresponding performance function. Probabilistic evaluations are performed by Monte Carlo simulation based on the SVM-KNN classifier. The ratio of the number of unstable samples to the total number of simulated samples is computed and is taken as the failure probability, which is validated and compared with the response surface method.
{"title":"Deterministic and probabilistic analysis of tunnel face stability using support vector machine","authors":"Bin Li, Yong Fu, Yi Hong, Zijun Cao","doi":"10.12989/GAE.2021.25.1.017","DOIUrl":"https://doi.org/10.12989/GAE.2021.25.1.017","url":null,"abstract":"This paper develops a convenient approach for deterministic and probabilistic evaluations of tunnel face stability using support vector machine classifiers. The proposed method is comprised of two major steps, i.e., construction of the training dataset and determination of instance-based classifiers. In step one, the orthogonal design is utilized to produce representative samples after the ranges and levels of the factors that influence tunnel face stability are specified. The training dataset is then labeled by two-dimensional strength reduction analyses embedded within OptumG2. For any unknown instance, the second step applies the training dataset for classification, which is achieved by an ad hoc Python program. The classification of unknown samples starts with selection of instance-based training samples using the k-nearest neighbors algorithm, followed by the construction of an instance-based SVM-KNN classifier. It eventually provides labels of the unknown instances, avoiding calculate its corresponding performance function. Probabilistic evaluations are performed by Monte Carlo simulation based on the SVM-KNN classifier. The ratio of the number of unstable samples to the total number of simulated samples is computed and is taken as the failure probability, which is validated and compared with the response surface method.","PeriodicalId":12602,"journal":{"name":"Geomechanics and Engineering","volume":"31 1","pages":"17"},"PeriodicalIF":3.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66475491","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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