Pub Date : 2021-01-01DOI: 10.12989/GAE.2021.25.2.075
Xianyu Xiong, Y. Xiong, Feng Zhang
Because the hydraulic/mechanical behaviour of unsaturated soil is more complicated than that of saturated soil, one of the most important issues in modelling unsaturated soil is to properly couple its stress-strain relationship with its water retention characteristics. Based on the results of a series of tests, the stress-strain relationship and the changes in suction and saturation of unsaturated completely decomposed granite (CDG, also called Masado) vary substantially under different loading/hydraulic conditions. To precisely model the hydraulic/mechanical behaviour of unsaturated Masado, in this study, the superloading concept was firstly introduced into an existing saturated/unsaturated constitutive model to consider the structural influences. Then a water retention curve (WRC) model considering the volumetric change in the soil, in which the skeleton and scanning curves of the water retention characteristics were assumed to shift in parallel in accordance with the change in the void ratio, was proposed. The proposed WRC model was incorporated into the constitutive model, and the validity of the newly proposed model was verified using the results of tests conducted on unsaturated Masado, including water retention, oedometer and triaxial tests. The accuracy of the proposed model in describing the stress-strain relationship and the variations in suction and saturation of unsaturated Masado is satisfactory.
{"title":"Modelling the hydraulic/mechanical behaviour of an unsaturated completely decomposed granite under various conditions","authors":"Xianyu Xiong, Y. Xiong, Feng Zhang","doi":"10.12989/GAE.2021.25.2.075","DOIUrl":"https://doi.org/10.12989/GAE.2021.25.2.075","url":null,"abstract":"Because the hydraulic/mechanical behaviour of unsaturated soil is more complicated than that of saturated soil, one of the most important issues in modelling unsaturated soil is to properly couple its stress-strain relationship with its water retention characteristics. Based on the results of a series of tests, the stress-strain relationship and the changes in suction and saturation of unsaturated completely decomposed granite (CDG, also called Masado) vary substantially under different loading/hydraulic conditions. To precisely model the hydraulic/mechanical behaviour of unsaturated Masado, in this study, the superloading concept was firstly introduced into an existing saturated/unsaturated constitutive model to consider the structural influences. Then a water retention curve (WRC) model considering the volumetric change in the soil, in which the skeleton and scanning curves of the water retention characteristics were assumed to shift in parallel in accordance with the change in the void ratio, was proposed. The proposed WRC model was incorporated into the constitutive model, and the validity of the newly proposed model was verified using the results of tests conducted on unsaturated Masado, including water retention, oedometer and triaxial tests. The accuracy of the proposed model in describing the stress-strain relationship and the variations in suction and saturation of unsaturated Masado is satisfactory.","PeriodicalId":12602,"journal":{"name":"Geomechanics and Engineering","volume":"86 1","pages":"75-87"},"PeriodicalIF":3.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66475776","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.2021.24.1.043
Ruiling Feng, Liyang Wang, K. Wei, Jiachen Zhao
Peatland is distributed in China widely, and organic matters in soil frequently induce problems in the construction and maintenance of highway engineering due to the high permeability and compressibility. In this paper, a selected site of Dali-Lijiang expressway was surveyed in China. A numerical model was built to predict the settlement of the foundation of the selected section employing the soft soil creep (SSC) model in PLAXIS 8.2. The model was subsequently verified by the result of field observance. Consequently, the parameters of 17 types of soils from different regions in China with organic contents varying from 1.1–74.9% were assigned to the numerical model to study the settlement characteristics. The calculated results showed that the duration of primary consolidation and proportion of primary settlement in the total settlement decreased with increasing organic content. Two empirical equations, for total consolidation settlement and secondary settlement, were proposed using multiple linear regression based on the calculated results from the numerical models. The analysis results of the significances of certain soil parameters demonstrated that the natural compression index, secondary compression index, cohesion and friction angle have significant linear relevance with both the total settlement and secondary settlement, while the initial coefficient of permeability exerts significant influence on the secondary settlement only.
{"title":"Consolidation settlement of soil foundations containing organic matters subjected to embankment load","authors":"Ruiling Feng, Liyang Wang, K. Wei, Jiachen Zhao","doi":"10.12989/GAE.2021.24.1.043","DOIUrl":"https://doi.org/10.12989/GAE.2021.24.1.043","url":null,"abstract":"Peatland is distributed in China widely, and organic matters in soil frequently induce problems in the construction and maintenance of highway engineering due to the high permeability and compressibility. In this paper, a selected site of Dali-Lijiang expressway was surveyed in China. A numerical model was built to predict the settlement of the foundation of the selected section employing the soft soil creep (SSC) model in PLAXIS 8.2. The model was subsequently verified by the result of field observance. Consequently, the parameters of 17 types of soils from different regions in China with organic contents varying from 1.1–74.9% were assigned to the numerical model to study the settlement characteristics. The calculated results showed that the duration of primary consolidation and proportion of primary settlement in the total settlement decreased with increasing organic content. Two empirical equations, for total consolidation settlement and secondary settlement, were proposed using multiple linear regression based on the calculated results from the numerical models. The analysis results of the significances of certain soil parameters demonstrated that the natural compression index, secondary compression index, cohesion and friction angle have significant linear relevance with both the total settlement and secondary settlement, while the initial coefficient of permeability exerts significant influence on the secondary settlement only.","PeriodicalId":12602,"journal":{"name":"Geomechanics and Engineering","volume":"24 1","pages":"43"},"PeriodicalIF":3.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66471744","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.2021.24.2.105
E. Güler, K. B. Afacan
Deformations in soils induced by dynamic loads cause damage to the structures above the soil layers. It is important for geotechnical engineering practice that how the soil behaves due to repeated loads and the necessary precautions to be taken accordingly. Turkey is one of the most important seismic regions in Europe and earthquake studies to be conducted in this area are intended to reduce the damage as a result of taking the necessary measures. To determine the properties of soils under dynamic loads, stress-controlled dynamic triaxial and resonant column tests can be performed. In this study, these experiments were implemented in the laboratory on the clayey sand soil samples obtained from Bilecik Sogut. To evaluate the effects of the confining pressure and rate of loading on the dynamic behavior of soils, samples were dynamically loaded by different rates at varying confining pressures. As a result, the changes in stress-strain properties of soils under dynamic loads were investigated. The alteration in behavior in terms of modulus reduction and damping ratios was obtained to vary a lot with the change of the lateral pressure on soil along with the frequency of the load.
{"title":"Dynamic behavior of clayey sand over a wide range using dynamic triaxial and resonant column tests","authors":"E. Güler, K. B. Afacan","doi":"10.12989/GAE.2021.24.2.105","DOIUrl":"https://doi.org/10.12989/GAE.2021.24.2.105","url":null,"abstract":"Deformations in soils induced by dynamic loads cause damage to the structures above the soil layers. It is important for geotechnical engineering practice that how the soil behaves due to repeated loads and the necessary precautions to be taken accordingly. Turkey is one of the most important seismic regions in Europe and earthquake studies to be conducted in this area are intended to reduce the damage as a result of taking the necessary measures. To determine the properties of soils under dynamic loads, stress-controlled dynamic triaxial and resonant column tests can be performed. In this study, these experiments were implemented in the laboratory on the clayey sand soil samples obtained from Bilecik Sogut. To evaluate the effects of the confining pressure and rate of loading on the dynamic behavior of soils, samples were dynamically loaded by different rates at varying confining pressures. As a result, the changes in stress-strain properties of soils under dynamic loads were investigated. The alteration in behavior in terms of modulus reduction and damping ratios was obtained to vary a lot with the change of the lateral pressure on soil along with the frequency of the load.","PeriodicalId":12602,"journal":{"name":"Geomechanics and Engineering","volume":"24 1","pages":"105"},"PeriodicalIF":3.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66472023","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.2021.24.3.253
Zhichao Wang, Yuantao Xie, J. Lai, Yongli Xie, Xulin Su, Yu-feng Shi, Chunxia Guo
The sufficient early strength of primary support is crucial for stabilizing the surroundings, especially for the tunnels constructed in soil. This paper introduces the Steel-Concrete Composite Support System (SCCS), a new support with high bearing capacity and flexible, rapid construction. The bearing characteristics and construction performance of SCCS were systematically studied using a three-dimensional numerical model. A sensitivity analysis was also performed. It was found that the stress of a π-shaped steel arch decreased with an increase in the thickness of the wall, and increased linearly with an increase in the rate of stress release. In the horizontal direction of the arch section, the nodal stresses of the crown and the shoulder gradually increased in longitudinally, and in the vertical direction, the nodal stresses gradually decreased from top to bottom. The stress distribution at the waist, however, was opposite to that at the crown and the shoulder. By analyzing the stress of the arch section under different installation gaps, the sectional stress evolution was found to have a step-growth trend at the crown and shoulder. The stress evolution at the waist is more likely to have a two-stage growth trend: a slow growth stage and a fast growth stage. The maximum tensile and compressive stresses of the secondary lining supported by SCCS were reduced on average by 38.0% and 49.0%, respectively, compared with the traditional support. The findings can provide a reference for the supporting technology in tunnels driven in loess.
{"title":"Designing an innovative support system in loess tunnel","authors":"Zhichao Wang, Yuantao Xie, J. Lai, Yongli Xie, Xulin Su, Yu-feng Shi, Chunxia Guo","doi":"10.12989/GAE.2021.24.3.253","DOIUrl":"https://doi.org/10.12989/GAE.2021.24.3.253","url":null,"abstract":"The sufficient early strength of primary support is crucial for stabilizing the surroundings, especially for the tunnels constructed in soil. This paper introduces the Steel-Concrete Composite Support System (SCCS), a new support with high bearing capacity and flexible, rapid construction. The bearing characteristics and construction performance of SCCS were systematically studied using a three-dimensional numerical model. A sensitivity analysis was also performed. It was found that the stress of a π-shaped steel arch decreased with an increase in the thickness of the wall, and increased linearly with an increase in the rate of stress release. In the horizontal direction of the arch section, the nodal stresses of the crown and the shoulder gradually increased in longitudinally, and in the vertical direction, the nodal stresses gradually decreased from top to bottom. The stress distribution at the waist, however, was opposite to that at the crown and the shoulder. By analyzing the stress of the arch section under different installation gaps, the sectional stress evolution was found to have a step-growth trend at the crown and shoulder. The stress evolution at the waist is more likely to have a two-stage growth trend: a slow growth stage and a fast growth stage. The maximum tensile and compressive stresses of the secondary lining supported by SCCS were reduced on average by 38.0% and 49.0%, respectively, compared with the traditional support. The findings can provide a reference for the supporting technology in tunnels driven in loess.","PeriodicalId":12602,"journal":{"name":"Geomechanics and Engineering","volume":"24 1","pages":"253-266"},"PeriodicalIF":3.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66472056","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.2021.24.4.389
H. Xing, Hao Zhang, Liangliang Liu, Yong Luo
Pile foundation is a typical form of bridge foundation and viaduct, and large-diameter rock-socketed piles are typically adopted in bridges with long span or high piers. To investigate the effect of a mountain slope with a deep overburden layer on the bearing characteristics of large-diameter rock-socketed piles, four centrifuge model tests of single piles on different slopes (0o, 15o, 30o and 45o) were carried out to investigate the effect of slope on the bearing characteristics of piles. In addition, three pile group tests with different slope (0o, 30o and 45o) were also performed to explore the effect of slope on the bearing characteristics of the pile group. The results of the single pile tests indicate that the slope with a deep overburden layer not only accelerates the drag force of the pile with the increasing slope, but also causes the bending moment to move down owing to the increase in the unsymmetrical pressure around the pile. As the slope increases from 0o to 45o, the drag force of the pile is significantly enlarged and the axial force of the pile reduces to beyond 12%. The position of the maximum bending moment of the pile shifts downward, while the magnitude becomes larger. Meanwhile, the slope results in the reduction in the shaft resistance of the pile, and the maximum value at the front side of the pile is 3.98% less than at its rear side at a 45o slope. The load-sharing ratio of the tip resistance of the pile is increased from 5.49% to 12.02%. The results of the pile group tests show that the increase in the slope enhances the uneven distribution of the pile top reaction and yields a larger bending moment and different settlements on the pile cap, which might cause safety issues to bridge structures.
{"title":"Effect of slope with overburden layer on the bearing behavior of large-diameter rock-socketed piles","authors":"H. Xing, Hao Zhang, Liangliang Liu, Yong Luo","doi":"10.12989/GAE.2021.24.4.389","DOIUrl":"https://doi.org/10.12989/GAE.2021.24.4.389","url":null,"abstract":"Pile foundation is a typical form of bridge foundation and viaduct, and large-diameter rock-socketed piles are typically adopted in bridges with long span or high piers. To investigate the effect of a mountain slope with a deep overburden layer on the bearing characteristics of large-diameter rock-socketed piles, four centrifuge model tests of single piles on different slopes (0o, 15o, 30o and 45o) were carried out to investigate the effect of slope on the bearing characteristics of piles. In addition, three pile group tests with different slope (0o, 30o and 45o) were also performed to explore the effect of slope on the bearing characteristics of the pile group. The results of the single pile tests indicate that the slope with a deep overburden layer not only accelerates the drag force of the pile with the increasing slope, but also causes the bending moment to move down owing to the increase in the unsymmetrical pressure around the pile. As the slope increases from 0o to 45o, the drag force of the pile is significantly enlarged and the axial force of the pile reduces to beyond 12%. The position of the maximum bending moment of the pile shifts downward, while the magnitude becomes larger. Meanwhile, the slope results in the reduction in the shaft resistance of the pile, and the maximum value at the front side of the pile is 3.98% less than at its rear side at a 45o slope. The load-sharing ratio of the tip resistance of the pile is increased from 5.49% to 12.02%. The results of the pile group tests show that the increase in the slope enhances the uneven distribution of the pile top reaction and yields a larger bending moment and different settlements on the pile cap, which might cause safety issues to bridge structures.","PeriodicalId":12602,"journal":{"name":"Geomechanics and Engineering","volume":"24 1","pages":"389"},"PeriodicalIF":3.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66472714","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.2021.24.4.359
H. Nasab, S. Karimi-Nasab, H. Jalalifar
Joint roughness is combination of primary and secondary roughness. Ordinarily primary roughness is a geostatistical part of a joint surface that has a periodic nature but secondary roughness or unevenness is a statistical part of that which have a random nature. Using roughness generating algorithms is a useful method for evaluation of joint roughness. In this paper after determining geostatistical parameters of the joint profile, were presented two roughness generating algorithms using Mount-Carlo method for evaluation of primary (GJRGAP) and secondary (GJRGAS) roughness. These based on geostatistical parameters (range and sill) and statistical parameters (standard deviation of asperities height, SDH, and standard deviation of asperities angle, SDA) for generation two-dimensional joint roughness profiles. In this study different geostatistical regions were defined depending on the range and SDH. As SDH increases, the height of the generated asperities increases and asperities become sharper and at a specific range (a specific curve) relation between SDH and SDA is linear. As the range in GJRGAP becomes larger (the base of the asperities) the shape of asperities becomes flatter. The results illustrate that joint profiles have larger SDA with increase of SDH and decrease of range. Consequencely increase of SDA leads to joint roughness parameters such Z2, Z3 and Rp increases. The results showed that secondary roughness or unevenness has a great influence on roughness values. In general, it can be concluded that the shape and size of asperities are appropriate parameters to approach the field scale from the laboratory scale.
{"title":"Geostatistical algorithm for evaluation of primary and secondary roughness","authors":"H. Nasab, S. Karimi-Nasab, H. Jalalifar","doi":"10.12989/GAE.2021.24.4.359","DOIUrl":"https://doi.org/10.12989/GAE.2021.24.4.359","url":null,"abstract":"Joint roughness is combination of primary and secondary roughness. Ordinarily primary roughness is a geostatistical part of a joint surface that has a periodic nature but secondary roughness or unevenness is a statistical part of that which have a random nature. Using roughness generating algorithms is a useful method for evaluation of joint roughness. In this paper after determining geostatistical parameters of the joint profile, were presented two roughness generating algorithms using Mount-Carlo method for evaluation of primary (GJRGAP) and secondary (GJRGAS) roughness. These based on geostatistical parameters (range and sill) and statistical parameters (standard deviation of asperities height, SDH, and standard deviation of asperities angle, SDA) for generation two-dimensional joint roughness profiles. In this study different geostatistical regions were defined depending on the range and SDH. As SDH increases, the height of the generated asperities increases and asperities become sharper and at a specific range (a specific curve) relation between SDH and SDA is linear. As the range in GJRGAP becomes larger (the base of the asperities) the shape of asperities becomes flatter. The results illustrate that joint profiles have larger SDA with increase of SDH and decrease of range. Consequencely increase of SDA leads to joint roughness parameters such Z2, Z3 and Rp increases. The results showed that secondary roughness or unevenness has a great influence on roughness values. In general, it can be concluded that the shape and size of asperities are appropriate parameters to approach the field scale from the laboratory scale.","PeriodicalId":12602,"journal":{"name":"Geomechanics and Engineering","volume":"24 1","pages":"359"},"PeriodicalIF":3.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66472966","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.2021.25.2.111
L. Dimitraki, B. Christaras, Nikolas Arampelos
Large deformation and rapid pressure propagation take place inside the rock mass under the dynamic loads caused by the explosives, on quarry faces in order to extract aggregate material. The complexity of the science of rock blasting is due to a number of factors that affect the phenomenon. However, blasting engineering computations could be facilitated by innovative software algorithms in order to determine the results of the violent explosion, since field experiments are particularly difficult to be conducted. The present research focuses on the design of a Finite Element Analysis (FEA) code, for investigating in detail the behavior of limestone under the blasting effect of Ammonium Nitrate & Fuel Oil (ANFO). Specifically, the manuscript presents the FEA models and the relevant transient analysis results, simulating the blasting process for three types of limestone, ranging from poor to very good quality. The Finite Element code was developed by applying the Jones-Wilkins-Lee (JWL) equation of state to describe the thermodynamic state of ANFO and the pressure dependent Drucker-Prager failure criterion to define the limestone plasticity behavior, under blasting induced, high rate stress. A progressive damage model was also used in order to define the stiffness degradation and destruction of the material. This paper performs a comparative analysis and quantifies the phenomena regarding pressure, stress distribution and energy balance, for three types of limestone. The ultimate goal of this research is to provide an answer for a number of scientific questions, considering various phenomena taking place during the explosion event, using advanced computational tools.
{"title":"Investigation of blasting impact on limestone of varying quality using FEA","authors":"L. Dimitraki, B. Christaras, Nikolas Arampelos","doi":"10.12989/GAE.2021.25.2.111","DOIUrl":"https://doi.org/10.12989/GAE.2021.25.2.111","url":null,"abstract":"Large deformation and rapid pressure propagation take place inside the rock mass under the dynamic loads caused by the explosives, on quarry faces in order to extract aggregate material. The complexity of the science of rock blasting is due to a number of factors that affect the phenomenon. However, blasting engineering computations could be facilitated by innovative software algorithms in order to determine the results of the violent explosion, since field experiments are particularly difficult to be conducted. The present research focuses on the design of a Finite Element Analysis (FEA) code, for investigating in detail the behavior of limestone under the blasting effect of Ammonium Nitrate & Fuel Oil (ANFO). Specifically, the manuscript presents the FEA models and the relevant transient analysis results, simulating the blasting process for three types of limestone, ranging from poor to very good quality. The Finite Element code was developed by applying the Jones-Wilkins-Lee (JWL) equation of state to describe the thermodynamic state of ANFO and the pressure dependent Drucker-Prager failure criterion to define the limestone plasticity behavior, under blasting induced, high rate stress. A progressive damage model was also used in order to define the stiffness degradation and destruction of the material. This paper performs a comparative analysis and quantifies the phenomena regarding pressure, stress distribution and energy balance, for three types of limestone. The ultimate goal of this research is to provide an answer for a number of scientific questions, considering various phenomena taking place during the explosion event, using advanced computational tools.","PeriodicalId":12602,"journal":{"name":"Geomechanics and Engineering","volume":"25 1","pages":"111"},"PeriodicalIF":3.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66476011","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.2021.25.4.317
D. J. Armaghani, A. Mamou, Chrysanthos Maraveas, P. Roussis, Vassilis G. Siorikis, A. Skentou, P. G. Asteris
This paper reports the results of advanced data analysis involving artificial neural networks for the prediction of the unconfined compressive strength of granite using only two non-destructive test indexes. A data-independent site-independent unbiased database comprising 182 datasets from non-destructive tests reported in the literature was compiled and used to train and develop artificial neural networks for the prediction of the unconfined compressive strength of granite. The results show that the optimum artificial network developed in this research predicts the unconfined compressive strength of weak to very strong granites (20.3-198.15MPa) with less than ±20% deviation from the experimental data for 70% of the specimen and significantly outperforms a number of available models available in the literature. The results also raise interesting questions with regards to the suitability of the Pearson correlation coefficient in assessing the prediction accuracy of models.
{"title":"Predicting the unconfined compressive strength of granite using only two non-destructive test indexes","authors":"D. J. Armaghani, A. Mamou, Chrysanthos Maraveas, P. Roussis, Vassilis G. Siorikis, A. Skentou, P. G. Asteris","doi":"10.12989/GAE.2021.25.4.317","DOIUrl":"https://doi.org/10.12989/GAE.2021.25.4.317","url":null,"abstract":"This paper reports the results of advanced data analysis involving artificial neural networks for the prediction of the unconfined compressive strength of granite using only two non-destructive test indexes. A data-independent site-independent unbiased database comprising 182 datasets from non-destructive tests reported in the literature was compiled and used to train and develop artificial neural networks for the prediction of the unconfined compressive strength of granite. The results show that the optimum artificial network developed in this research predicts the unconfined compressive strength of weak to very strong granites (20.3-198.15MPa) with less than ±20% deviation from the experimental data for 70% of the specimen and significantly outperforms a number of available models available in the literature. The results also raise interesting questions with regards to the suitability of the Pearson correlation coefficient in assessing the prediction accuracy of models.","PeriodicalId":12602,"journal":{"name":"Geomechanics and Engineering","volume":"25 1","pages":"317"},"PeriodicalIF":3.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66476967","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.2021.25.6.481
Hao Wu, D. Ma, A. Spearing, G. Zhao
Hazardous failure phenomena such as rock bursts and slabbing failure frequently occur in deep hardrock tunnels, thus understanding the failure phenomena and mechanisms of the stress regime on tunnels is extremely critical. In this study, the tunnel system in a rock mass was physically modelled as a number of scaled openings in rock specimens, and the mechanical behavior of specimens having one to four horseshoe-shaped openings under uniaxial compression were investigated systematically. During the tests, the digital image correlation (DIC) and acoustic emission (AE) techniques were jointly employed to monitor the fracture response of specimens. After which, the stress distributions in the specimens were numerically analyzed and the stress concentration factor on the periphery of the opening was calculated. The results show that the number of openings have a significant impact on the weakening effect of rock mechanical properties. The progressive cracking process of the specimens with openings evolves from first-tensile cracks through second-tensile cracks and spalling cracks to shear cracks, and the crack threshold stresses are measured. Two failure modes are formed: shear failure and shear-tensile failure. According to the stress distribution law around the opening, the crack initiation mechanism can be fully explained. This research provides an insight to failure mechanism of hardrock tunnel.
{"title":"Fracture response and mechanisms of brittle rock with different numbers of openings under uniaxial loading","authors":"Hao Wu, D. Ma, A. Spearing, G. Zhao","doi":"10.12989/GAE.2021.25.6.481","DOIUrl":"https://doi.org/10.12989/GAE.2021.25.6.481","url":null,"abstract":"Hazardous failure phenomena such as rock bursts and slabbing failure frequently occur in deep hardrock tunnels, thus understanding the failure phenomena and mechanisms of the stress regime on tunnels is extremely critical. In this study, the tunnel system in a rock mass was physically modelled as a number of scaled openings in rock specimens, and the mechanical behavior of specimens having one to four horseshoe-shaped openings under uniaxial compression were investigated systematically. During the tests, the digital image correlation (DIC) and acoustic emission (AE) techniques were jointly employed to monitor the fracture response of specimens. After which, the stress distributions in the specimens were numerically analyzed and the stress concentration factor on the periphery of the opening was calculated. The results show that the number of openings have a significant impact on the weakening effect of rock mechanical properties. The progressive cracking process of the specimens with openings evolves from first-tensile cracks through second-tensile cracks and spalling cracks to shear cracks, and the crack threshold stresses are measured. Two failure modes are formed: shear failure and shear-tensile failure. According to the stress distribution law around the opening, the crack initiation mechanism can be fully explained. This research provides an insight to failure mechanism of hardrock tunnel.","PeriodicalId":12602,"journal":{"name":"Geomechanics and Engineering","volume":"25 1","pages":"481"},"PeriodicalIF":3.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66477090","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.2021.26.3.227
F. Huang, Di Wang, N. Xiao, Ruo-chen Ou
The study of failure mode for the soil in front of a shield tunnel face is a key challenge for tunnel engineering, especially when drilling under the water table. This work aims to study face stability of a shield tunnel under the water table based on an blow-out failure mechanism in the framework of the upper bound theorem of limit analysis in conjunction with variational principle. The seepage force in the seepage field is derived, and seepage force is regarded as an external force which is introduced in the upper bound calculation. Based on the failure characteristic of the blow-out failure for the soil in front of a shield tunnel face, a upper bound failure mechanism is constructed. Using this mechanism, the equation of the failure surface is obtained and the shapes of the failure surfaces for different parameters are plotted. By studying the influence of various parameters on the shape of failure surfaces, the changing laws of the shape of the failure surface for different parameters are obtained.
{"title":"Upper bound limit analysis of blow-out failure mode of excavation face of shield tunnel considering groundwater seepage","authors":"F. Huang, Di Wang, N. Xiao, Ruo-chen Ou","doi":"10.12989/GAE.2021.26.3.227","DOIUrl":"https://doi.org/10.12989/GAE.2021.26.3.227","url":null,"abstract":"The study of failure mode for the soil in front of a shield tunnel face is a key challenge for tunnel engineering, especially when drilling under the water table. This work aims to study face stability of a shield tunnel under the water table based on an blow-out failure mechanism in the framework of the upper bound theorem of limit analysis in conjunction with variational principle. The seepage force in the seepage field is derived, and seepage force is regarded as an external force which is introduced in the upper bound calculation. Based on the failure characteristic of the blow-out failure for the soil in front of a shield tunnel face, a upper bound failure mechanism is constructed. Using this mechanism, the equation of the failure surface is obtained and the shapes of the failure surfaces for different parameters are plotted. By studying the influence of various parameters on the shape of failure surfaces, the changing laws of the shape of the failure surface for different parameters are obtained.","PeriodicalId":12602,"journal":{"name":"Geomechanics and Engineering","volume":"26 1","pages":"227"},"PeriodicalIF":3.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66478139","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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