Fernando Fante, Maria Mariana de Sousa Rocha, E. Moreira, P. Prietto, F. D. Rosa, Luizmar da Silva Lopes Júnior, F. Almeida, N. Consoli
Residual soils are found all around the world. Their behaviour is different from "classic" soils due to the structure resulting from the geological formation processes, which can eventually undergo degradation under static and cyclic loads, with a decrease in both stiffness and strength. In this context, this study aimed to evaluate the behaviour of weakly bonded residual soil in the face of loading and unloading cycles using field plate load tests. Preliminary field and laboratory tests were carried out to characterize the residual soil at the experimental site. The monotonic and cyclic plate load tests - with circular and square plates – were performed under three different load amplitudes. The results showed no shape effect of the loaded area for both monotonic and cyclic loading, considering the same loading pattern. Also, there is a threshold load, which indicates a yielding point and a change in soil behaviour and can be estimated from simple laboratory tests. Below this load, the residual soil presented a rigid behaviour even when subjected to cyclic loads.
{"title":"Behaviour of a Weakly Bonded Residual Soil Subjected to Monotonic and Cyclic Loading","authors":"Fernando Fante, Maria Mariana de Sousa Rocha, E. Moreira, P. Prietto, F. D. Rosa, Luizmar da Silva Lopes Júnior, F. Almeida, N. Consoli","doi":"10.1680/jgeen.21.00143","DOIUrl":"https://doi.org/10.1680/jgeen.21.00143","url":null,"abstract":"Residual soils are found all around the world. Their behaviour is different from \"classic\" soils due to the structure resulting from the geological formation processes, which can eventually undergo degradation under static and cyclic loads, with a decrease in both stiffness and strength. In this context, this study aimed to evaluate the behaviour of weakly bonded residual soil in the face of loading and unloading cycles using field plate load tests. Preliminary field and laboratory tests were carried out to characterize the residual soil at the experimental site. The monotonic and cyclic plate load tests - with circular and square plates – were performed under three different load amplitudes. The results showed no shape effect of the loaded area for both monotonic and cyclic loading, considering the same loading pattern. Also, there is a threshold load, which indicates a yielding point and a change in soil behaviour and can be estimated from simple laboratory tests. Below this load, the residual soil presented a rigid behaviour even when subjected to cyclic loads.","PeriodicalId":54572,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Geotechnical Engineering","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2022-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80475078","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lucio Di Matteo PhD Associate Professor, Department of Physics and Geology, University of Perugia, Perugia, Italy Giovanni Spagnoli PhD, MBA Global Project and Technology Manager Underground Construction, MBCC Group, Trostberg, Germany Amin Soltani PhD Lecturer, Institute of Innovation, Science and Sustainability, Federation University, Churchill, VIC, Australia; Honorary Fellow, Department of Infrastructure Engineering, Faculty of Engineering and Information Technology, The University of Melbourne, Parkville, VIC, Australia (Orcid:0000-0002-0483-7487) (corresponding author: a.soltani@federation.edu.au) Mahdieh Azimi MSc PhD candidate, College of Engineering and Aviation, School of Engineering and Technology, CQUniversity, Melbourne, VIC, Australia (Orcid:0000-0001-6061-7991) Brendan C. O’Kelly PhD, FTCD Associate Professor, Department of Civil, Structural and Environmental Engineering, Trinity College Dublin, Dublin, Ireland (Orcid:0000-0002-1343-4428)
Lucio Di Matteo博士，意大利佩鲁贾大学物理与地质系副教授，Giovanni Spagnoli博士，MBA全球项目与技术经理，德国MBCC集团地下建设，Trostberg，澳大利亚维多利亚州丘吉尔联邦大学创新、科学与可持续发展研究所Amin Soltani博士讲师;澳大利亚维多利亚州帕克维尔市墨尔本大学工程与信息技术学院基础设施工程系荣誉院士(Orcid:0000-0002-0483-7487)(通讯作者:a.soltani@federation.edu.au) Mahdieh Azimi硕士研究生，工程与航空学院，工程与技术学院，墨尔本，维多利亚州，澳大利亚(Orcid:0000-0001-6061-7991) Brendan C. O 'Kelly博士，FTCD副教授，土木，结构与环境工程系，都柏林，都柏林，爱尔兰(Orcid:0000-0002-1343-4428)
{"title":"Discussion: Predicting Compaction Properties of Soils at Different Compaction Efforts","authors":"A. Soltani, M. Azimi, B. O’Kelly","doi":"10.1680/jgeen.22.00053","DOIUrl":"https://doi.org/10.1680/jgeen.22.00053","url":null,"abstract":"Lucio Di Matteo PhD Associate Professor, Department of Physics and Geology, University of Perugia, Perugia, Italy Giovanni Spagnoli PhD, MBA Global Project and Technology Manager Underground Construction, MBCC Group, Trostberg, Germany Amin Soltani PhD Lecturer, Institute of Innovation, Science and Sustainability, Federation University, Churchill, VIC, Australia; Honorary Fellow, Department of Infrastructure Engineering, Faculty of Engineering and Information Technology, The University of Melbourne, Parkville, VIC, Australia (Orcid:0000-0002-0483-7487) (corresponding author: a.soltani@federation.edu.au) Mahdieh Azimi MSc PhD candidate, College of Engineering and Aviation, School of Engineering and Technology, CQUniversity, Melbourne, VIC, Australia (Orcid:0000-0001-6061-7991) Brendan C. O’Kelly PhD, FTCD Associate Professor, Department of Civil, Structural and Environmental Engineering, Trinity College Dublin, Dublin, Ireland (Orcid:0000-0002-1343-4428)","PeriodicalId":54572,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Geotechnical Engineering","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2022-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83521793","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Anjerick Topacio, Yit-Jin Chen, K. Phoon, Chong Tang
Representative compression interpretation criteria were analysed in this study to assess their relative merits and interrelationships when applied to drilled shafts socketed into rocks. Results of load tests around the world were gathered and collated into a database CYCU/RockSocket/50 for the assessment. Each of the applied interpretation criteria was then evaluated and compared with one another and with the results of the interpretations of drilled shafts in varying soil conditions and post-grouted drilled shafts. To further assess the behaviour of drilled shafts socketed into rocks, interpreted side and end bearing resistances were also determined. The mean interpreted capacities and displacements were higher for drilled shafts socketed into rocks when compared to drilled shafts in soils, but are at comparable ranges with tip post-grouted drilled shafts. On this basis, recommendations regarding specific interpretation criteria, which are advantageous for design displacement requirements under 12 mm for serviceability and displacements on the range of 53 mm to 71 mm for ultimate limit states, were established. Finally, behavioural assessments of the normalized load-displacement curves were extensively done using hyperbolic equations to test their effectivity to CYCU/RockSocket/50.
{"title":"Evaluation of Compression Interpretation Criteria for Drilled Shafts Socketed into Rocks","authors":"Anjerick Topacio, Yit-Jin Chen, K. Phoon, Chong Tang","doi":"10.1680/jgeen.21.00120","DOIUrl":"https://doi.org/10.1680/jgeen.21.00120","url":null,"abstract":"Representative compression interpretation criteria were analysed in this study to assess their relative merits and interrelationships when applied to drilled shafts socketed into rocks. Results of load tests around the world were gathered and collated into a database CYCU/RockSocket/50 for the assessment. Each of the applied interpretation criteria was then evaluated and compared with one another and with the results of the interpretations of drilled shafts in varying soil conditions and post-grouted drilled shafts. To further assess the behaviour of drilled shafts socketed into rocks, interpreted side and end bearing resistances were also determined. The mean interpreted capacities and displacements were higher for drilled shafts socketed into rocks when compared to drilled shafts in soils, but are at comparable ranges with tip post-grouted drilled shafts. On this basis, recommendations regarding specific interpretation criteria, which are advantageous for design displacement requirements under 12 mm for serviceability and displacements on the range of 53 mm to 71 mm for ultimate limit states, were established. Finally, behavioural assessments of the normalized load-displacement curves were extensively done using hyperbolic equations to test their effectivity to CYCU/RockSocket/50.","PeriodicalId":54572,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Geotechnical Engineering","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2022-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89290687","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zhijian Yan, Junru Zhang, Yi Dai, Bo Yan, Xiaorui Jiang
Under the conditions of karst development and soft upper and hard lower strata, the ground settlement control of tunnel under airport taxiway construction is stricter than that of ordinary tunnel. Tunnel construction methods and karst disposal measures are also particularly important. It is an engineering problem that needs to be solved urgently to ensure the safe passage of the tunnel under airport taxiways without suspension. Taking the intercity railway tunnel under the taxiways T3 and T4 of Guangzhou Baiyun International Airport as the research object, this study carried out theoretical analysis and field test on Karst Treatment Measures and surface settlement control measures. The Karst Treatment Measures under different condition and the "Pile Supporting Plate" structure system are proposed to support the taxiway. The effect of the system is analyzed by numerical method, and the on-site surface settlement is monitored. The research results shows that the maximum settlement of T3 and T4 taxiway surface monitored on site are 5.90mm and the differential settlement is 0.12‰. The numerical simulation results are similar to this value, and do not exceed the settlement control standard of taxiway. Through the research, the key technologies for the construction technique of tunnels under airport taxiway of airport taxiway under tunnel in karst area and upper soft and lower hard strata are is formed, the karst disposal measures for tunnel construction in karst areas is summarized and the "pile support plate" protection system for ground settlement control when tunnels under pass the airport without suspension is proposed ,which can provide reference for similar projects.
{"title":"Surface Control Techniques for Tunnels in Karst Areas Under Crossing Airport Taxiways","authors":"Zhijian Yan, Junru Zhang, Yi Dai, Bo Yan, Xiaorui Jiang","doi":"10.1680/jgeen.22.00014","DOIUrl":"https://doi.org/10.1680/jgeen.22.00014","url":null,"abstract":"Under the conditions of karst development and soft upper and hard lower strata, the ground settlement control of tunnel under airport taxiway construction is stricter than that of ordinary tunnel. Tunnel construction methods and karst disposal measures are also particularly important. It is an engineering problem that needs to be solved urgently to ensure the safe passage of the tunnel under airport taxiways without suspension. Taking the intercity railway tunnel under the taxiways T3 and T4 of Guangzhou Baiyun International Airport as the research object, this study carried out theoretical analysis and field test on Karst Treatment Measures and surface settlement control measures. The Karst Treatment Measures under different condition and the \"Pile Supporting Plate\" structure system are proposed to support the taxiway. The effect of the system is analyzed by numerical method, and the on-site surface settlement is monitored. The research results shows that the maximum settlement of T3 and T4 taxiway surface monitored on site are 5.90mm and the differential settlement is 0.12‰. The numerical simulation results are similar to this value, and do not exceed the settlement control standard of taxiway. Through the research, the key technologies for the construction technique of tunnels under airport taxiway of airport taxiway under tunnel in karst area and upper soft and lower hard strata are is formed, the karst disposal measures for tunnel construction in karst areas is summarized and the \"pile support plate\" protection system for ground settlement control when tunnels under pass the airport without suspension is proposed ,which can provide reference for similar projects.","PeriodicalId":54572,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Geotechnical Engineering","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2022-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83306723","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xiao Bing Xu, Y. Ying, Q. Hu, Yun-chang Chen, Huashan Fang, Haibo Zhu, Minyun Hu
The design of a large excavation using a braced wall system (BWS) with H-shaped steel (HS) struts is introduced. In-situ axial loading tests were conducted to study the load transfer and deformation mechanisms of a HS strut with double splay supports. The monitoring results indicate that the outer splay support withstands the most lateral earth pressure (48.5%), followed by the inner splay support (35.6%) and BC segment of end support (15.9%). The safety redundancies of strength and stability for the outer and inner splay supports, AB and BC segments of end support are all larger than 1.59. The axial deformations of the middle support and the whole strut tend to increase linearly with the loading process. Using the monitored total load of hydraulic jacks, the value of KT″ of the whole strut is estimated to be 158∼189 MN/m. The modified value of KT″ (KT″ba/S) of the whole strut is 2.2∼2.6 MN/m. It is close to the lower limit of the suggested range (2.5∼3.5 MN/m) in the Chinese standard. The monitored data of typical safety control parameters during soil excavation and the monitored results during in-situ loading tests indicate good performance of the BWS with HS struts in this project.
{"title":"In-situ axial loading tests on H-shaped steel strut with double splay supports","authors":"Xiao Bing Xu, Y. Ying, Q. Hu, Yun-chang Chen, Huashan Fang, Haibo Zhu, Minyun Hu","doi":"10.1680/jgeen.21.00102","DOIUrl":"https://doi.org/10.1680/jgeen.21.00102","url":null,"abstract":"The design of a large excavation using a braced wall system (BWS) with H-shaped steel (HS) struts is introduced. In-situ axial loading tests were conducted to study the load transfer and deformation mechanisms of a HS strut with double splay supports. The monitoring results indicate that the outer splay support withstands the most lateral earth pressure (48.5%), followed by the inner splay support (35.6%) and BC segment of end support (15.9%). The safety redundancies of strength and stability for the outer and inner splay supports, AB and BC segments of end support are all larger than 1.59. The axial deformations of the middle support and the whole strut tend to increase linearly with the loading process. Using the monitored total load of hydraulic jacks, the value of KT″ of the whole strut is estimated to be 158∼189 MN/m. The modified value of KT″ (KT″ba/S) of the whole strut is 2.2∼2.6 MN/m. It is close to the lower limit of the suggested range (2.5∼3.5 MN/m) in the Chinese standard. The monitored data of typical safety control parameters during soil excavation and the monitored results during in-situ loading tests indicate good performance of the BWS with HS struts in this project.","PeriodicalId":54572,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Geotechnical Engineering","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2022-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84769176","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Houssem Eddine Lanabi, S. Benmebarek, N. Benmebarek
In this paper, numerical computations using FLAC code (Fast Lagrangian Analyses of Continua) are carried out to evaluate the passive earth pressure magnitude and distribution against a retaining wall subjected to different wall movement modes: translation (T) mode, rotation about bottom (RB) mode and rotation about top (RT) mode. In agreement with classical solutions, the results indicate that in T mode, passive earth pressure distribution is substantially hydrostatic with depth for all wall displacement stages. However, when the mode of rotation either RT or RB is considered, a clear non-linear distribution highly affected by wall displacement magnitude is noticed. For RT mode, due to arching effect, the increase of the earth pressure behind the lower half of the wall is more pronounced with wall displacement affecting hardly the centroid of the passive load distribution located bellow the common one-third of the wall height. In RB mode, as the wall rotation progresses, the passive earth pressure mobilized in upper part of the wall increases and its distribution gradually changes from nonlinear to linear distribution. Compared with previous experimental results available in literature, mobilized passive earth pressure in RB and RT modes needs more displacement than T mode.
本文利用FLAC程序(Fast Lagrangian Analyses of Continua)对挡土墙在平移(T)模式、绕底旋转(RB)模式和绕顶旋转(RT)模式下的被动土压力大小和分布进行了数值计算。与经典解一致，结果表明，在T型模式下，被动土压力随深度的分布基本上是静力的。然而，当考虑旋转模式RT或RB时，注意到一个明显的非线性分布，受壁面位移大小的影响很大。对于RT模式，由于拱效应，墙后下半部分土压力增加更为明显，墙体位移对位于墙高普通三分之一以下的被动荷载分布质心影响不大。在RB模式下，随着墙体旋转的进行，墙体上部动员的被动土压力增大，其分布逐渐由非线性变为线性分布。与文献中已有的实验结果相比，RB和RT模式下的被动土压力比T模式下需要更大的位移。
{"title":"Passive earth pressure under various modes of wall movements by numerical approach","authors":"Houssem Eddine Lanabi, S. Benmebarek, N. Benmebarek","doi":"10.1680/jgeen.21.00199","DOIUrl":"https://doi.org/10.1680/jgeen.21.00199","url":null,"abstract":"In this paper, numerical computations using FLAC code (Fast Lagrangian Analyses of Continua) are carried out to evaluate the passive earth pressure magnitude and distribution against a retaining wall subjected to different wall movement modes: translation (T) mode, rotation about bottom (RB) mode and rotation about top (RT) mode. In agreement with classical solutions, the results indicate that in T mode, passive earth pressure distribution is substantially hydrostatic with depth for all wall displacement stages. However, when the mode of rotation either RT or RB is considered, a clear non-linear distribution highly affected by wall displacement magnitude is noticed. For RT mode, due to arching effect, the increase of the earth pressure behind the lower half of the wall is more pronounced with wall displacement affecting hardly the centroid of the passive load distribution located bellow the common one-third of the wall height. In RB mode, as the wall rotation progresses, the passive earth pressure mobilized in upper part of the wall increases and its distribution gradually changes from nonlinear to linear distribution. Compared with previous experimental results available in literature, mobilized passive earth pressure in RB and RT modes needs more displacement than T mode.","PeriodicalId":54572,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Geotechnical Engineering","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2022-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78673738","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Yeasin Mostafiz, Naveel Islam, M. Kausar Alam, M. Zoynul Abedin, R. Dey, Aurun Valsangkar
The bounce and penetrometer resistance of a cricket pitch for three different crack-control conditions was investigated. Fifteen miniature cricket pitches were prepared using the conventional procedure, natural grassroots, and geotextile roofing felts combined with varying fine sand and bentonite clay proportions. The rebound ball height and ground penetrometer resistances were measured with a designed bounce meter and pocket penetrometer respectively. In addition, properties of the pitch soils such as crack width, moisture content and field densities were measured. The results of the test programme indicated that the pitch with the geotextile crack-control system provided a higher coefficient of restitution and penetrometer resistance than the other two systems. Furthermore, the test results suggested that the clay content should be kept between 50% to 65 % under a geotextile roofing felt to reduce significant growth of crack widths for a good cricket pitch. Finally, several correlation equations are proposed relating the restitution coefficient and penetrometer resistance with the index and physical properties of pitch soil for use in pitch characterisation.
{"title":"Performance of geotextile roofing felts and natural grass roots in a cricket pitch","authors":"M. Yeasin Mostafiz, Naveel Islam, M. Kausar Alam, M. Zoynul Abedin, R. Dey, Aurun Valsangkar","doi":"10.1680/jgeen.21.00008a","DOIUrl":"https://doi.org/10.1680/jgeen.21.00008a","url":null,"abstract":"The bounce and penetrometer resistance of a cricket pitch for three different crack-control conditions was investigated. Fifteen miniature cricket pitches were prepared using the conventional procedure, natural grassroots, and geotextile roofing felts combined with varying fine sand and bentonite clay proportions. The rebound ball height and ground penetrometer resistances were measured with a designed bounce meter and pocket penetrometer respectively. In addition, properties of the pitch soils such as crack width, moisture content and field densities were measured. The results of the test programme indicated that the pitch with the geotextile crack-control system provided a higher coefficient of restitution and penetrometer resistance than the other two systems. Furthermore, the test results suggested that the clay content should be kept between 50% to 65 % under a geotextile roofing felt to reduce significant growth of crack widths for a good cricket pitch. Finally, several correlation equations are proposed relating the restitution coefficient and penetrometer resistance with the index and physical properties of pitch soil for use in pitch characterisation.","PeriodicalId":54572,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Geotechnical Engineering","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2022-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74928465","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Stability assessment and design of stepped excavation slopes are of great practical significance and require explicit consideration of the three-dimensional (3D) effect and the suction-related effects. In the realm of 3D kinematic limit analysis theorem, this paper presents a semi-analytical method to quantify the suction impact in the stability assessments of stepped excavation slopes. The influences of surcharge load and seismic excitation are both considered from a kinematic perspective. Numerical experiments were conducted regarding the roles of soil suction, 3D effect, surcharge loads and seismic actions in the safety assessments. An example is presented to show the practical use of this method in engineering practice with respect to the determination of the optimum shape of a stepped excavation slope that characterized with fixed slope toe and slope crest positions. The results demonstrate that the stability of stepped excavation slopes can be improved by 10% ∼ 25% compared with those of single-stage slopes and the optimum depth coefficient (αopt) falls in 0.55 ∼ 0.7 for most cases. For steeper excavation slopes, αopt might exceed this range, while for gentler slopes, αopt tends to be smaller than this range. The critical slip surface and the 3D effect tends to be more pronounced as the surcharge load increases.
{"title":"Kinematic limit analysis of unsaturated stepped excavation slopes subjected to surcharge loads","authors":"Long Wang, Meijuan Xu, Jie Li, E. Zhou, You Gao","doi":"10.1680/jgeen.21.00220","DOIUrl":"https://doi.org/10.1680/jgeen.21.00220","url":null,"abstract":"Stability assessment and design of stepped excavation slopes are of great practical significance and require explicit consideration of the three-dimensional (3D) effect and the suction-related effects. In the realm of 3D kinematic limit analysis theorem, this paper presents a semi-analytical method to quantify the suction impact in the stability assessments of stepped excavation slopes. The influences of surcharge load and seismic excitation are both considered from a kinematic perspective. Numerical experiments were conducted regarding the roles of soil suction, 3D effect, surcharge loads and seismic actions in the safety assessments. An example is presented to show the practical use of this method in engineering practice with respect to the determination of the optimum shape of a stepped excavation slope that characterized with fixed slope toe and slope crest positions. The results demonstrate that the stability of stepped excavation slopes can be improved by 10% ∼ 25% compared with those of single-stage slopes and the optimum depth coefficient (αopt) falls in 0.55 ∼ 0.7 for most cases. For steeper excavation slopes, αopt might exceed this range, while for gentler slopes, αopt tends to be smaller than this range. The critical slip surface and the 3D effect tends to be more pronounced as the surcharge load increases.","PeriodicalId":54572,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Geotechnical Engineering","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2022-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75094638","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Recently use of commercial software for analysis and design of rock slopes, underground structures, mining projects, the foundation of any infrastructure projects, piles, etc. becoming more popular and widely used. But sometimes, this software has many limitations and cannot be used directly for finding out the strength and deformation behavior of rock joints when joints are subjected to external load because of the construction of different projects. Correct prediction of strength and deformation behavior of rock joints are important for safe, economical, and sustainable design. In the present work, strength and deformation behavior of unfilled and infilled rock joints have been studied numerically by using one of the commercial software Universal Distinct Element Code (UDEC) under different boundary conditions like constant normal stiffness (CNS) and constant normal load (CNL) boundary conditions. The numerical model results are compared with experimental results of the test performed on a physical model. The strength predicted by the numerical model is in close agreement with experimental results at low initial normal stress and for CNL boundary conditions, as the asperity degradation during shearing process is almost same throughout the test. The numerical model cannot correctly predict the shear strength of rock joints under CNS boundary conditions and at high normal stress for both CNL and CNS conditions, because of the degradation in the asperity during shearing process and available model dosenot consider this effect. Hence, UDEC code has been modified in the present study for its acceptability under both CNL and CNS boundary conditins and at high initial normal stress at CNL boundary conditions. A comparison of predicted value with experimental results indicated most of the prediction lies in the prediction bend of 95%.
{"title":"Shear behaviour of infilled rock joints under different boundary conditions","authors":"A. Shrivastava, K. S. Rao","doi":"10.1680/jgeen.21.00060","DOIUrl":"https://doi.org/10.1680/jgeen.21.00060","url":null,"abstract":"Recently use of commercial software for analysis and design of rock slopes, underground structures, mining projects, the foundation of any infrastructure projects, piles, etc. becoming more popular and widely used. But sometimes, this software has many limitations and cannot be used directly for finding out the strength and deformation behavior of rock joints when joints are subjected to external load because of the construction of different projects. Correct prediction of strength and deformation behavior of rock joints are important for safe, economical, and sustainable design. In the present work, strength and deformation behavior of unfilled and infilled rock joints have been studied numerically by using one of the commercial software Universal Distinct Element Code (UDEC) under different boundary conditions like constant normal stiffness (CNS) and constant normal load (CNL) boundary conditions. The numerical model results are compared with experimental results of the test performed on a physical model. The strength predicted by the numerical model is in close agreement with experimental results at low initial normal stress and for CNL boundary conditions, as the asperity degradation during shearing process is almost same throughout the test. The numerical model cannot correctly predict the shear strength of rock joints under CNS boundary conditions and at high normal stress for both CNL and CNS conditions, because of the degradation in the asperity during shearing process and available model dosenot consider this effect. Hence, UDEC code has been modified in the present study for its acceptability under both CNL and CNS boundary conditins and at high initial normal stress at CNL boundary conditions. A comparison of predicted value with experimental results indicated most of the prediction lies in the prediction bend of 95%.","PeriodicalId":54572,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Geotechnical Engineering","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2022-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74746268","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yang Sun, Zhenxue Gu, Zhenyang Xu, Chongxiao Wang, Dewei Song
A 1257 m-long special-shaped deep excavation was performed in the city center of Nanjing, China. Full-width and half-width top-down construction methods were adopted. Based on the long-term monitoring data of the project, this paper analyzed the evolution characteristics of the diaphragm wall deformation, the ground settlement and the settlement of adjacent buildings and discussed their interrelationships and their relationships with the excavation process, structural system and geological conditions. The results showed that the horizontal displacement of the diaphragm walls was less than 1% of the excavation depth and that the position of the maximum horizontal displacement was generally located from 4 m above the excavation surface to the vicinity of the excavation surface. The influence range of excavation on the surrounding ground settlement was mostly within three times the excavation depth, and the ground settlement varied from 0.1%∼0.5% of the excavation depth to 0.3∼5 times the maximum horizontal displacement of the diaphragm wall. During the construction process, the settlement rate suddenly increased only when the excavation reached the soft soil layer. Building settlement was related to the excavation deformation, structure forms, foundation types and distance to the foundation pit.
{"title":"Performance of a long irregular excavation by the top-down technique in a downtown area","authors":"Yang Sun, Zhenxue Gu, Zhenyang Xu, Chongxiao Wang, Dewei Song","doi":"10.1680/jgeen.21.00156","DOIUrl":"https://doi.org/10.1680/jgeen.21.00156","url":null,"abstract":"A 1257 m-long special-shaped deep excavation was performed in the city center of Nanjing, China. Full-width and half-width top-down construction methods were adopted. Based on the long-term monitoring data of the project, this paper analyzed the evolution characteristics of the diaphragm wall deformation, the ground settlement and the settlement of adjacent buildings and discussed their interrelationships and their relationships with the excavation process, structural system and geological conditions. The results showed that the horizontal displacement of the diaphragm walls was less than 1% of the excavation depth and that the position of the maximum horizontal displacement was generally located from 4 m above the excavation surface to the vicinity of the excavation surface. The influence range of excavation on the surrounding ground settlement was mostly within three times the excavation depth, and the ground settlement varied from 0.1%∼0.5% of the excavation depth to 0.3∼5 times the maximum horizontal displacement of the diaphragm wall. During the construction process, the settlement rate suddenly increased only when the excavation reached the soft soil layer. Building settlement was related to the excavation deformation, structure forms, foundation types and distance to the foundation pit.","PeriodicalId":54572,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Geotechnical Engineering","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2022-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85241786","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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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