This paper presents a practical procedure for determining soil parameters used when analysing the deformation of peat ground by finite element analysis (FE analysis) using the Cam clay model. In practice, FE analysis has not been used frequently to predict the deformation of peat ground, even though FE analysis can be a powerful tool for its prediction. The main reason is that a practical method for determining parameters has not been established. In this paper, firstly, the remarkable correlation between the soil parameters required for FE analysis using the Cam clay model and the natural water content (w n ) and ignition loss (L i ), respectively, of peat and organic clay is presented. Next, based on this correlation, a flowchart for determining the soil parameters of peat and organic clay is proposed. By using this chart, it is possible to directly determine the soil parameters from triaxial compression, oedometer and other detailed tests or to estimate the soil parameters from w n , L i and other physical indexes. We also conducted a trial embankment on peat ground in Hokkaido, Japan. FE analysis was performed on the trial embankment using the proposed procedure for determining soil parameters. The results of the FE analysis corresponded to the measured settlement behaviour in the trial embankment with an accuracy in the range of −4% to +8%. The FE analysis results also expressed the measured behaviour of pore water pressure and lateral and vertical displacement in the trial embankment very well.
{"title":"A practical procedure for determining soil parameters of peat for finite element analysis using the cam clay model","authors":"Hirochika Hayashi, Nobutaka Yamazoe","doi":"10.1680/jgeen.22.00063","DOIUrl":"https://doi.org/10.1680/jgeen.22.00063","url":null,"abstract":"This paper presents a practical procedure for determining soil parameters used when analysing the deformation of peat ground by finite element analysis (FE analysis) using the Cam clay model. In practice, FE analysis has not been used frequently to predict the deformation of peat ground, even though FE analysis can be a powerful tool for its prediction. The main reason is that a practical method for determining parameters has not been established. In this paper, firstly, the remarkable correlation between the soil parameters required for FE analysis using the Cam clay model and the natural water content (w n ) and ignition loss (L i ), respectively, of peat and organic clay is presented. Next, based on this correlation, a flowchart for determining the soil parameters of peat and organic clay is proposed. By using this chart, it is possible to directly determine the soil parameters from triaxial compression, oedometer and other detailed tests or to estimate the soil parameters from w n , L i and other physical indexes. We also conducted a trial embankment on peat ground in Hokkaido, Japan. FE analysis was performed on the trial embankment using the proposed procedure for determining soil parameters. The results of the FE analysis corresponded to the measured settlement behaviour in the trial embankment with an accuracy in the range of −4% to +8%. The FE analysis results also expressed the measured behaviour of pore water pressure and lateral and vertical displacement in the trial embankment very well.","PeriodicalId":54572,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Geotechnical Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135141127","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}
In many settlement prediction methods, the creep settlement of shallow foundations on sand has been either disregarded or accounted for using time correction factors that lack a reliable basis. These existing settlement correction factors for creep have mainly been derived from a restricted number of long-term settlement measurements, and do not consider the influence of factors such as the load level, rate of load application and properties of soil below the foundation. A newly proposed one-dimensional (1D) elasto-viscoplastic macro-element is employed in this study to investigate the factors influencing the time-dependent behaviour of shallow foundations on sand. The safety factor of the foundation, the creep characteristic of the soils and the duration of load application are found to have an important effect on the post-construction settlement development. The simulation results are used to develop an enhanced settlement correction factor for creep, which takes into account the identified factors. The improved settlement correction factor is shown to be comparable to existing ones when the safety factor of the foundation is 3. The effectiveness of the proposed settlement correction factor is demonstrated using creep settlement measurements from one field footing test and two case histories.
{"title":"An improved creep correction factor for the settlement of shallow foundations on sand based on macro-element simulations","authors":"Bo Liu, Jianfeng Xue, Barry M. Lehane, Zhenyu Yin","doi":"10.1680/jgeen.23.00049","DOIUrl":"https://doi.org/10.1680/jgeen.23.00049","url":null,"abstract":"In many settlement prediction methods, the creep settlement of shallow foundations on sand has been either disregarded or accounted for using time correction factors that lack a reliable basis. These existing settlement correction factors for creep have mainly been derived from a restricted number of long-term settlement measurements, and do not consider the influence of factors such as the load level, rate of load application and properties of soil below the foundation. A newly proposed one-dimensional (1D) elasto-viscoplastic macro-element is employed in this study to investigate the factors influencing the time-dependent behaviour of shallow foundations on sand. The safety factor of the foundation, the creep characteristic of the soils and the duration of load application are found to have an important effect on the post-construction settlement development. The simulation results are used to develop an enhanced settlement correction factor for creep, which takes into account the identified factors. The improved settlement correction factor is shown to be comparable to existing ones when the safety factor of the foundation is 3. The effectiveness of the proposed settlement correction factor is demonstrated using creep settlement measurements from one field footing test and two case histories.","PeriodicalId":54572,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Geotechnical Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135241043","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}
Luiz Augusto da Silva Florêncio, Mauricio Ehrlich, Seyed Hamed Mirmoradi
This paper numerically evaluates the effect of secondary reinforcement on the value and location of the maximum reinforcement load along the primary reinforcement layers (T max ) in geosynthetic-reinforced soil (GRS) walls under working stress conditions. Data from three instrumented sections of a well-instrumented GRS wall were used for model validation. A parametric study was carried out considering different controlling factors (i.e. the vertical reinforcement spacing, facing type and secondary reinforcement stiffness and length). The results show that for a constant relative soil-reinforcement stiffness index, the variation of the vertical reinforcement spacing and stiffness may not affect the location and normalised value of T max . In general, for the conventionally used type of reinforcement, the secondary reinforcement inclusion reduces T max to values lower than those corresponding to the active condition (K a ). For a given facing type, the combined effect of the secondary reinforcement length and stiffness is the main factor that controls the T max location. In general, increasing the secondary reinforcement stiffness and length moves the location of T max from the back of the facing to a distance corresponding to the length of the secondary reinforcement layers. In addition, for this condition, a flexible face model performs similarly to a block face model.
{"title":"Secondary reinforcement effect on the value and location of maximum reinforcement load","authors":"Luiz Augusto da Silva Florêncio, Mauricio Ehrlich, Seyed Hamed Mirmoradi","doi":"10.1680/jgeen.23.00048","DOIUrl":"https://doi.org/10.1680/jgeen.23.00048","url":null,"abstract":"This paper numerically evaluates the effect of secondary reinforcement on the value and location of the maximum reinforcement load along the primary reinforcement layers (T max ) in geosynthetic-reinforced soil (GRS) walls under working stress conditions. Data from three instrumented sections of a well-instrumented GRS wall were used for model validation. A parametric study was carried out considering different controlling factors (i.e. the vertical reinforcement spacing, facing type and secondary reinforcement stiffness and length). The results show that for a constant relative soil-reinforcement stiffness index, the variation of the vertical reinforcement spacing and stiffness may not affect the location and normalised value of T max . In general, for the conventionally used type of reinforcement, the secondary reinforcement inclusion reduces T max to values lower than those corresponding to the active condition (K a ). For a given facing type, the combined effect of the secondary reinforcement length and stiffness is the main factor that controls the T max location. In general, increasing the secondary reinforcement stiffness and length moves the location of T max from the back of the facing to a distance corresponding to the length of the secondary reinforcement layers. In addition, for this condition, a flexible face model performs similarly to a block face model.","PeriodicalId":54572,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Geotechnical Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135293554","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}
This paper describes an analytical method for investigating the tunnel–pile interaction for new tunnels crossing the pile foundation of the Shenzhen Bay Bridge, with a case study using a cavity expansion-based model. The three-dimensional analytical model developed in this study evaluates the ground deformation and pile response induced by the construction of tunnels for the two Metro #13 lines and the Wanghai Road tunnel, and assesses the effectiveness of mitigation measures such as ground stabilisation and isolation walls. The study reveals significant vertical displacement and surface settlement caused by the Wanghai Road tunnel, and horizontal deformation and bending moments in specific pile foundations. The results show that reinforcement measures can effectively control formation deformation disturbance, and metro jet system isolation walls can limit horizontal and vertical displacements caused by excavation. To ensure the safe operation of the Shenzhen Bay Bridge, the study highlights the importance of comprehensively evaluating the safety of shield crossing schemes. The proposed analytical method could also serve as a pre-design tool and reference for optimising tunnel construction, providing valuable guidance for future reinforcement schemes. In general, this study provides significant insights into the tunnel–pile interaction, which will be useful for bridge and tunnel engineering design and construction.
{"title":"Analytical method for new tunnel crossing pile foundation of existing bridge: a case study","authors":"Kuan-Jun Wang, Guo-Yao Li, Pin-Qiang Mo, Zhongqi Shi, Fu-Bin Chen, Xin-Sheng Yin","doi":"10.1680/jgeen.23.00060","DOIUrl":"https://doi.org/10.1680/jgeen.23.00060","url":null,"abstract":"This paper describes an analytical method for investigating the tunnel–pile interaction for new tunnels crossing the pile foundation of the Shenzhen Bay Bridge, with a case study using a cavity expansion-based model. The three-dimensional analytical model developed in this study evaluates the ground deformation and pile response induced by the construction of tunnels for the two Metro #13 lines and the Wanghai Road tunnel, and assesses the effectiveness of mitigation measures such as ground stabilisation and isolation walls. The study reveals significant vertical displacement and surface settlement caused by the Wanghai Road tunnel, and horizontal deformation and bending moments in specific pile foundations. The results show that reinforcement measures can effectively control formation deformation disturbance, and metro jet system isolation walls can limit horizontal and vertical displacements caused by excavation. To ensure the safe operation of the Shenzhen Bay Bridge, the study highlights the importance of comprehensively evaluating the safety of shield crossing schemes. The proposed analytical method could also serve as a pre-design tool and reference for optimising tunnel construction, providing valuable guidance for future reinforcement schemes. In general, this study provides significant insights into the tunnel–pile interaction, which will be useful for bridge and tunnel engineering design and construction.","PeriodicalId":54572,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Geotechnical Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135923894","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}
Laís Rodrigues da Costa Chaves, Karla Salvagni Heineck, Hugo Carlos Scheuermann Filho, Helder Mansur Chaves, João Vítor de Azambuja Carvalho, Alexia Cindy Wagner, João Paulo de Sousa Silva, Nilo Cesar Consoli
The dry stacking of filtered tailings emerges as an alternative to deal with the safety-related problems of conventional slurry disposal in reservoirs behind upstream dams. Incorporating a cementing agent into the tailings before compaction can enhance the overall geomechanical behaviour of these structures, giving rise to more stable and safer stackings. However, few dry stacks are in operation worldwide, and their field performance needs to be better understood. Also, the cement addition provides further challenges to the design of these structures. Thus, obtaining reliable laboratory data for properly designing these tailings storage facilities is essential. Accordingly, this paper evaluates the mechanical behaviour of artificially cemented iron ore tailings for dry stacking purposes, focusing on comparing the responses between on-field compacted samples and laboratory-assembled specimens. For such, the following tests were carried out: ultrasonic pulse velocity, unconfined compression, split tensile, and triaxial compression. Both the stiffness and the strength data could be well-described by the porosity/cement index, and, despite minor differences, there was a good agreement between the responses of laboratory and field compacted samples. These findings highlight the laboratory procedures’ adequacy in reflecting the material's real on-field conditions.
{"title":"Field and laboratory study of compacted filtered iron ore tailings-Portland cement blends for dry stacking purposes","authors":"Laís Rodrigues da Costa Chaves, Karla Salvagni Heineck, Hugo Carlos Scheuermann Filho, Helder Mansur Chaves, João Vítor de Azambuja Carvalho, Alexia Cindy Wagner, João Paulo de Sousa Silva, Nilo Cesar Consoli","doi":"10.1680/jgeen.23.00097","DOIUrl":"https://doi.org/10.1680/jgeen.23.00097","url":null,"abstract":"The dry stacking of filtered tailings emerges as an alternative to deal with the safety-related problems of conventional slurry disposal in reservoirs behind upstream dams. Incorporating a cementing agent into the tailings before compaction can enhance the overall geomechanical behaviour of these structures, giving rise to more stable and safer stackings. However, few dry stacks are in operation worldwide, and their field performance needs to be better understood. Also, the cement addition provides further challenges to the design of these structures. Thus, obtaining reliable laboratory data for properly designing these tailings storage facilities is essential. Accordingly, this paper evaluates the mechanical behaviour of artificially cemented iron ore tailings for dry stacking purposes, focusing on comparing the responses between on-field compacted samples and laboratory-assembled specimens. For such, the following tests were carried out: ultrasonic pulse velocity, unconfined compression, split tensile, and triaxial compression. Both the stiffness and the strength data could be well-described by the porosity/cement index, and, despite minor differences, there was a good agreement between the responses of laboratory and field compacted samples. These findings highlight the laboratory procedures’ adequacy in reflecting the material's real on-field conditions.","PeriodicalId":54572,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Geotechnical Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134911700","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}
Tunnel excavation in geologically challenging areas can lead to slope instability and consequent landslides, which pose a serious threat to the integrity of the tunnel lining. To address this issue, a study was conducted to investigate the stability of the tunnel-landslide system using the finite difference method (FDM) based on the Hanshankou Tunnel of the Shaoguan-Xinfeng Expressway. A plane strain model was used to examine the effect of various treatment measures on the system, and the strength reduction (incremental) method was employed to determine the range of initial slope safety factors applicable to different treatment measures, with the maximum shear strain increment serving as the criterion. The ‘anti-slip pile + anchor frame beam’ reinforcement system was found to be the most effective solution, reducing daily deformation by 60.1% after implementation. The results indicated that the pile-anchor reinforcement system can significantly mitigate landslide creep, and the corresponding treatment measures can be categorized based on the critical slope safety factor under different conditions.
{"title":"Treatment measures for the creep-slip phase of landslides induced by twin tunnels: a case study","authors":"Junru Zhang, Jianchi Ma, Kaimeng Ma, Yumei Tan, Zhijian Yan, Jimeng Feng","doi":"10.1680/jgeen.22.00239","DOIUrl":"https://doi.org/10.1680/jgeen.22.00239","url":null,"abstract":"Tunnel excavation in geologically challenging areas can lead to slope instability and consequent landslides, which pose a serious threat to the integrity of the tunnel lining. To address this issue, a study was conducted to investigate the stability of the tunnel-landslide system using the finite difference method (FDM) based on the Hanshankou Tunnel of the Shaoguan-Xinfeng Expressway. A plane strain model was used to examine the effect of various treatment measures on the system, and the strength reduction (incremental) method was employed to determine the range of initial slope safety factors applicable to different treatment measures, with the maximum shear strain increment serving as the criterion. The ‘anti-slip pile + anchor frame beam’ reinforcement system was found to be the most effective solution, reducing daily deformation by 60.1% after implementation. The results indicated that the pile-anchor reinforcement system can significantly mitigate landslide creep, and the corresponding treatment measures can be categorized based on the critical slope safety factor under different conditions.","PeriodicalId":54572,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Geotechnical Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134911704","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}
Red clay is prone to cracking in desiccating environments. The crisscross cracks compromise the soil structures and induce the instability of slopes. Under natural hygrothermal conditions, a desiccation test of red clay slurry was performed with a self-made device and digital image correlation (DIC) technology to study crack evolution, quantitatively analyse the relationships between moisture content, displacement, strain, and cracks. Results indicate that cracks usually initiate by subdividing and intersect at right angles with other cracks. Main cracks initiate earliest and have the longest duration, with stabilised main cracks being longer and wider than secondary cracks. DIC technology can dynamically monitor crack evolution. Based on strain concentration areas, the location of early-initiated crack initiation and the propagation trend could be preliminarily predicted. The failure strain in cracking was related to the moisture content, and crack evolution was related to the red clay Atterberg limits. The soil shrinkage exhibited anisotropic behaviour, with greater vertical shrinkage at the soil clod centre compared to the edges. In contrast, the horizontal displacement and maximum principal strain at the soil clod centre were smaller than those at the edges. Those findings contribute to providing guidance for formulating engineering geological hazard control measures.
{"title":"Quantitative analysis of the desiccation crack evolution in red clay based on digital image correlation technology","authors":"Aijun Chen, Chaohua Li, Chuanyang Ding","doi":"10.1680/jgeen.22.00186","DOIUrl":"https://doi.org/10.1680/jgeen.22.00186","url":null,"abstract":"Red clay is prone to cracking in desiccating environments. The crisscross cracks compromise the soil structures and induce the instability of slopes. Under natural hygrothermal conditions, a desiccation test of red clay slurry was performed with a self-made device and digital image correlation (DIC) technology to study crack evolution, quantitatively analyse the relationships between moisture content, displacement, strain, and cracks. Results indicate that cracks usually initiate by subdividing and intersect at right angles with other cracks. Main cracks initiate earliest and have the longest duration, with stabilised main cracks being longer and wider than secondary cracks. DIC technology can dynamically monitor crack evolution. Based on strain concentration areas, the location of early-initiated crack initiation and the propagation trend could be preliminarily predicted. The failure strain in cracking was related to the moisture content, and crack evolution was related to the red clay Atterberg limits. The soil shrinkage exhibited anisotropic behaviour, with greater vertical shrinkage at the soil clod centre compared to the edges. In contrast, the horizontal displacement and maximum principal strain at the soil clod centre were smaller than those at the edges. Those findings contribute to providing guidance for formulating engineering geological hazard control measures.","PeriodicalId":54572,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Geotechnical Engineering","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2023-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83343556","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}
In the last decades, considerable attempts in geotechnical study have been made to reduce plastic waste by recycling and reusing. This study aimed to reuse waste plastic mixed with sand for geotechnical application. To this end, large-scale oedometer experiments were carried out to examine the compressibility of Bandar-e Anzali sands stabilized with plastic waste-originated high-density polyethylene (HDPE). Bandar-e Anzali is a populated coastal city in the vicinity of the Caspian Sea (Northern Iran). Large-scale oedometer and direct shear tests were performed to study the applicability of HDPE chips mixed with sand at various HDPE contents (0, 2, 4, 6, and 8%). Based on the experimental tests, the addition of plastic waste to the soil improved the soil's strength, significantly raised its compressibility, and decreased the undrained elasticity modulus. By adding 8% HDPE, the constrained compression modulus decreased to 50% at a pressure of 300 kPa due to the elastic deformability of HDPEs. However, at higher relative density, adding HDPE by more than 4% did not affect the coefficient of lateral earth pressure at rest.
{"title":"Experimental investigation into the compression characteristics and lateral earth pressure coefficient of Bandar-e Anzali sand in Caspian Sea shore mixed with HDPE","authors":"Masoomeh Khodabakhshi, M. Arabani","doi":"10.1680/jgeen.22.00174","DOIUrl":"https://doi.org/10.1680/jgeen.22.00174","url":null,"abstract":"In the last decades, considerable attempts in geotechnical study have been made to reduce plastic waste by recycling and reusing. This study aimed to reuse waste plastic mixed with sand for geotechnical application. To this end, large-scale oedometer experiments were carried out to examine the compressibility of Bandar-e Anzali sands stabilized with plastic waste-originated high-density polyethylene (HDPE). Bandar-e Anzali is a populated coastal city in the vicinity of the Caspian Sea (Northern Iran). Large-scale oedometer and direct shear tests were performed to study the applicability of HDPE chips mixed with sand at various HDPE contents (0, 2, 4, 6, and 8%). Based on the experimental tests, the addition of plastic waste to the soil improved the soil's strength, significantly raised its compressibility, and decreased the undrained elasticity modulus. By adding 8% HDPE, the constrained compression modulus decreased to 50% at a pressure of 300 kPa due to the elastic deformability of HDPEs. However, at higher relative density, adding HDPE by more than 4% did not affect the coefficient of lateral earth pressure at rest.","PeriodicalId":54572,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Geotechnical Engineering","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2023-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89573166","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}
A wide variety of instrumentation was deployed during construction of the sprayed concrete lined tunnels at Heathrow Express Terminal 4 Station in the mid-1990s, some of which continues to function and be accessible for the taking of readings today. This paper presents a nearly 20-year history of stress in the primary lining of the Concourse Tunnel measured using radial and tangential pressure cells on and in the sprayed concrete. Data from tangential pressure cells require careful interpretation and the new and complete methodology for achieving reliable results described in Jones & Clayton (2021) was used to provide the stress history from construction into the long-term. This is a unique case study, in terms of both the detail of the measurements and interpretation and the time period over which measurements have been taken. The results show that pressure cells are very sensitive and respond to changes in stress due to nearby construction activities, and that after construction has ceased, stresses stabilise at a value well below full overburden pressure (the vertical total stress at tunnel axis level).
{"title":"Stresses in sprayed concrete tunnel linings at Heathrow Terminal 4","authors":"B. Jones, C. Grand, C. Clayton","doi":"10.1680/jgeen.22.00054","DOIUrl":"https://doi.org/10.1680/jgeen.22.00054","url":null,"abstract":"A wide variety of instrumentation was deployed during construction of the sprayed concrete lined tunnels at Heathrow Express Terminal 4 Station in the mid-1990s, some of which continues to function and be accessible for the taking of readings today. This paper presents a nearly 20-year history of stress in the primary lining of the Concourse Tunnel measured using radial and tangential pressure cells on and in the sprayed concrete. Data from tangential pressure cells require careful interpretation and the new and complete methodology for achieving reliable results described in Jones & Clayton (2021) was used to provide the stress history from construction into the long-term. This is a unique case study, in terms of both the detail of the measurements and interpretation and the time period over which measurements have been taken. The results show that pressure cells are very sensitive and respond to changes in stress due to nearby construction activities, and that after construction has ceased, stresses stabilise at a value well below full overburden pressure (the vertical total stress at tunnel axis level).","PeriodicalId":54572,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Geotechnical Engineering","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2023-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79396882","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}
Land subsidence has threatened the safety of municipal infrastructures and even that of inhabitants. As one of the deformation monitoring methods, distributed optical fibre sensing (DOFS) technology has been developed for the investigation of land subsidence. The deformation coordination between the optical fibre and soil (DCf-s) under different conditions is critical for land subsidence monitoring with DOFS. In this paper, a medium-size triaxial apparatus was modified for testing the DCf-s. Consolidated drained triaxial tests were conducted to investigate the effect of sand types on the DCf-s. By linearly fitting of the deformation of the sensing cable with that of the triaxial specimen, the other factors that affect the DCf-s, such as the confining pressure, dry or wet state of the soil, and cyclic variation of the loads, were discussed. The experiments reveal that better DCf-s comes with a larger particle size, poor gradation of sand, and larger confining pressure. The DCf-s of wet sand is better than that of dry sand. The DCf-s coefficient tends to be stable with increasing of loading cycles. The obtained DCf-s and its dependence on influencing factors can be used to modify the measured cable strain in practical land subsidence monitoring with DOFS.
{"title":"Experimental investigation on the deformation coordination between an optical fibre and backfilling sand of borehole","authors":"Hasanjan Yimit, Dan Zhang, Q. Luo, X. Gong, Hao Wang, Haiyang Liao","doi":"10.1680/jgeen.23.00055","DOIUrl":"https://doi.org/10.1680/jgeen.23.00055","url":null,"abstract":"Land subsidence has threatened the safety of municipal infrastructures and even that of inhabitants. As one of the deformation monitoring methods, distributed optical fibre sensing (DOFS) technology has been developed for the investigation of land subsidence. The deformation coordination between the optical fibre and soil (DCf-s) under different conditions is critical for land subsidence monitoring with DOFS. In this paper, a medium-size triaxial apparatus was modified for testing the DCf-s. Consolidated drained triaxial tests were conducted to investigate the effect of sand types on the DCf-s. By linearly fitting of the deformation of the sensing cable with that of the triaxial specimen, the other factors that affect the DCf-s, such as the confining pressure, dry or wet state of the soil, and cyclic variation of the loads, were discussed. The experiments reveal that better DCf-s comes with a larger particle size, poor gradation of sand, and larger confining pressure. The DCf-s of wet sand is better than that of dry sand. The DCf-s coefficient tends to be stable with increasing of loading cycles. The obtained DCf-s and its dependence on influencing factors can be used to modify the measured cable strain in practical land subsidence monitoring with DOFS.","PeriodicalId":54572,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Geotechnical Engineering","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2023-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75227771","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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