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Buddhima Indraratna - One of the best experts on this subject based on the ideXlab platform.
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Performance and prediction of vacuum consolidation behaviour at Port of Brisbane
2020Co-Authors: Buddhima Indraratna, Cholachat Rujikiatkamjorn, Xueyu Geng, Jayantha AmeratungaAbstract:Due to a projected increase in trade activities at the Port of Brisbane, new berths on Fisherman Islands at the mouth of the Brisbane River will be constructed in the outer area(235ha) close to the existing port facilities via land reclamation. A vacuum assisted Surcharge load in conjunction with prefabricated vertical drains was chosen to reduce the required consolidation time. The features of the combined vacuum and Surcharge Fill system and the construction of the embankment are described in this paper. A comparison of the performance of the vacuum combined Surcharge loading system with a standard Surcharge Fill emphasises the obvious advantages of vacuum consolidation. Field data is presented to show how the embankment performed during construction. An analytical solution for radial consolidation incorporating both time-dependent Surcharge loading and vacuum pressure is employed to calculate the settlements and associated excess pore pressures of the soft Holocene clay deposits. Disciplines Engineering | Science and Technology Studies Publication Details Indraratna, B., Rujikiatkamjorn, C., Geng, X. & Ameratunga, J. (2013). Performance and prediction of vacuum consolidation behaviour at Port of Brisbane. 18th International Conference on Soil Mechanics and Geotechnical Engineering (pp. 1497-2500). France: The French Society for Soil Mechanics and Geotechnical Engineering. This conference paper is available at Research Online: http://ro.uow.edu.au/eispapers/2550
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Performance and prediction of marine clay treated with vacuum and Surcharge consolidation at Port of Brisbane
2020Co-Authors: Buddhima Indraratna, A S Balasubramaniam, Cholachat Rujikiatkamjorn, Harry G. Poulos, Jayantha AmeratungaAbstract:Over the past decade the application of vacuum preloading for stabilising soft offshore-coastal clay in shallow water and other low-lying estuarine soils has become popular in Australia. Its cost effectiveness is a major factor in most projects in view of the significantly reduced time for achieving a relatively high degree of consolidation. Due to an increase in trade activities at the Port of Brisbane, new facilities on Fisherman Islands at the mouth of the Brisbane River will be constructed on the new outer area (235ha) adjacent to the existing port facilities via land reclamation. A vacuum assisted Surcharge load and conventional Surcharge scheme, in conjunction with prefabricated vertical drains, was selected to reduce the required consolidation time through the deeper layers of subsoil. The performance of a combined vacuum and Surcharge Fill system and construction of the embankment are described in this paper. A comparison of the performance of a combined vacuum and Surcharge loading system with a standard Surcharge Fill highlights the clear benefits of vacuum consolidation. Field monitoring data are presented to demonstrate how the embankment performed during construction. This paper also evaluates the relative performance of the two contrasting preloading systems (i.e. vacuum and non-vacuum system). An analytical solution for radial consolidation that considers both time-dependent Surcharge loading and vacuum pressure is proposed to predict the settlement and associated excess pore pressures of the soft Holocene clay deposits.
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Radial consolidation theories and numerical analysis of soft soil stabilisation via prefabricated vertical drains
2020Co-Authors: Buddhima Indraratna, Cholachat Rujikiatkamjorn, Rohan T WalkerAbstract:In this paper, an analytical solution based on actual radial soil permeability and compressibility is proposed considering the impact of parabolic variation of permeability in smear zone. The use of the spectral method for multilayered soil consolidation is introduced and verified. The Cavity Expansion Theory is employed to predict the extent of soil disturbance (smear zone) caused by the installation of mandrel driven vertical drains. The smear zone prediction is then compared to the data obtained from large-scale radial consolidation tests. Furthermore, the advantages and limitations of vacuum application through vertical drains are discussed using the proposed solutions. The applied vacuum pressure generates negative pore water pressure, resulting in an increase in effective stress within the soil, which leads to accelerated consolidation. Vacuum pressure is modelled as a distributed negative pressure (suction) along the drain length and across the soil surface. Analytical and numerical analyses incorporating the Authors’ equivalent plane strain solution are conducted to predict the excess pore pressures, lateral and vertical displacements. Application of the theoretical models for a selected case history is discussed and analysed, at the site of the 2nd Bangkok International Airport. The predictions are compared with the available field data, showing that an equivalent plane strain model can be used confidently to predict the performance with acceptable accuracy through rigorous mathematical modelling and numerical analysis. The research findings verify that the role of smear, drain unsaturation, and vacuum distribution can significantly affect the soil consolidation, hence, these aspects need to be modelled appropriately to obtain reliable predictions. INTRODUCTION Soft clay deposits usually have a low bearing capacity as well as excessive settlement characteristics. Therefore, it is necessary to improve the existing soft soils before commencing construction activities in order to prevent excessive and differential settlement (Richart, 1957). The application of vertical drains and preloading is a popular soil improvement technique. Vertical drains accelerate soil consolidation by providing short horizontal drainage paths for pore water flow, and are used worldwide in many soft soil improvement projects (Holtz et al., 1991; Indraratna et al., 1992; Indraratna and Redana, 2000). The utilisation of geosynthetic prefabricated vertical drains (PVDs) has become an economical and viable option because of their rapid installation with simple field equipment (Shang et al. 1998). In order to control the risk of embankment failure, Surcharge embankments are usually raised as a multi-stage exercise with rest periods provided between the loading stages (Jamiolkowski et al. 1983). This may not be possible with busy construction schedules. Application of vacuum load in addition to Surcharge Fill can further accelerate the rate of settlement to obtain the desired settlement without increasing the excess 1 Professor of Civil Engineering, Faculty of Engineering, University of Wollongong, Wollongong City, NSW 2522, Australia, E-mail: indra@uow.edu.au 2 Research Fellow, Faculty of Engineering, University of Wollongong, Wollongong City, NSW 2522, Australia 3 Research Associate, Faculty of Engineering, University of Wollongong, Wollongong City, NSW 2522, Australia pore pressure (Kjellman, 1952; Qian et al., 1992). This practice has been employed for land reclamation and port projects (Chu and Yan, 2005). The PVD system has also been employed to distribute vacuum pressure to deep subsoil layers, thereby increasing the consolidation rate. The consolidation process of the vacuum preloading in comparison with the conventional preloading is shown in Fig. (1).
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Performance of marine clay stabilised with vacuum pressure: Based on Queensland experience
Journal of rock mechanics and geotechnical engineering, 2019Co-Authors: Buddhima Indraratna, Cholachat Rujikiatkamjorn, Pankaj Baral, Jayantha AmeratungaAbstract:Abstract Stabilising soft marine clay and estuarine soils via vacuum preloading has become very popular in Australasia over the past decades because it is a cost-effective and time-efficient approach. In recent times, new land on areas outside but adjacent to existing port amenities, the Fisherman Islands at the Port of Brisbane (POB), was reclaimed to cater for an increase in trade activities. A vacuum preloading method combined with Surcharge to stabilise the deep layers of soil was used to enhance the application of prefabricated vertical drains (PVDs). This paper describes the performance of this combined Surcharge Fill and vacuum system under the embankment and also compares it with a Surcharge loading system to demonstrate the benefits of vacuum pressure over conventional Fill. The performance of this embankment is also presented in terms of field monitoring data, and the relative performance of the vacuum together with non-vacuum systems is evaluated. An analytical solution to radial consolidation with time-dependent Surcharge loading and vacuum pressure is also presented in order to predict the settlement and associated excess pore water pressure (EPWP) of deposits of thick soft clay.
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Monitoring of consolidation behaviour of marine clay treated with vacuum and Surcharge at the Port of Brisbane
Proceedings of the Ninth Symposium on Field Measurements in Geomechanics, 2015Co-Authors: Buddhima Indraratna, A S Balasubramaniam, Cholachat Rujikiatkamjorn, Jayantha Ameratunga, Harry G. Poulos, Darshana PereraAbstract:Over the past decade, the application of vacuum preloading for stabilising reclaimed soil and other low-lying estuarine soils has become popular in Australia. Its cost effectiveness is a governing factor in view of the reduced consolidation time to achieve a relatively high degree of consolidation. Due to demand in trade activities at the Port of Brisbane, new port facilities have been constructed on reclaimed land. A vacuum and Fill Surcharge, in conjunction with prefabricated vertical drains, was selected to accelerate consolidation time of the thick layers of subsoil. A performance comparison of a combined vacuum and Fill Surcharge loading system with a standard Surcharge Fill highlights the clear advantages of vacuum consolidation. Field data demonstrate how the embankment performed during construction. This paper also assesses the relative performance of the two contrasting preloading systems (i.e. vacuum and non-vacuum system).
Cholachat Rujikiatkamjorn - One of the best experts on this subject based on the ideXlab platform.
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Performance and prediction of vacuum consolidation behaviour at Port of Brisbane
2020Co-Authors: Buddhima Indraratna, Cholachat Rujikiatkamjorn, Xueyu Geng, Jayantha AmeratungaAbstract:Due to a projected increase in trade activities at the Port of Brisbane, new berths on Fisherman Islands at the mouth of the Brisbane River will be constructed in the outer area(235ha) close to the existing port facilities via land reclamation. A vacuum assisted Surcharge load in conjunction with prefabricated vertical drains was chosen to reduce the required consolidation time. The features of the combined vacuum and Surcharge Fill system and the construction of the embankment are described in this paper. A comparison of the performance of the vacuum combined Surcharge loading system with a standard Surcharge Fill emphasises the obvious advantages of vacuum consolidation. Field data is presented to show how the embankment performed during construction. An analytical solution for radial consolidation incorporating both time-dependent Surcharge loading and vacuum pressure is employed to calculate the settlements and associated excess pore pressures of the soft Holocene clay deposits. Disciplines Engineering | Science and Technology Studies Publication Details Indraratna, B., Rujikiatkamjorn, C., Geng, X. & Ameratunga, J. (2013). Performance and prediction of vacuum consolidation behaviour at Port of Brisbane. 18th International Conference on Soil Mechanics and Geotechnical Engineering (pp. 1497-2500). France: The French Society for Soil Mechanics and Geotechnical Engineering. This conference paper is available at Research Online: http://ro.uow.edu.au/eispapers/2550
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Performance and prediction of marine clay treated with vacuum and Surcharge consolidation at Port of Brisbane
2020Co-Authors: Buddhima Indraratna, A S Balasubramaniam, Cholachat Rujikiatkamjorn, Harry G. Poulos, Jayantha AmeratungaAbstract:Over the past decade the application of vacuum preloading for stabilising soft offshore-coastal clay in shallow water and other low-lying estuarine soils has become popular in Australia. Its cost effectiveness is a major factor in most projects in view of the significantly reduced time for achieving a relatively high degree of consolidation. Due to an increase in trade activities at the Port of Brisbane, new facilities on Fisherman Islands at the mouth of the Brisbane River will be constructed on the new outer area (235ha) adjacent to the existing port facilities via land reclamation. A vacuum assisted Surcharge load and conventional Surcharge scheme, in conjunction with prefabricated vertical drains, was selected to reduce the required consolidation time through the deeper layers of subsoil. The performance of a combined vacuum and Surcharge Fill system and construction of the embankment are described in this paper. A comparison of the performance of a combined vacuum and Surcharge loading system with a standard Surcharge Fill highlights the clear benefits of vacuum consolidation. Field monitoring data are presented to demonstrate how the embankment performed during construction. This paper also evaluates the relative performance of the two contrasting preloading systems (i.e. vacuum and non-vacuum system). An analytical solution for radial consolidation that considers both time-dependent Surcharge loading and vacuum pressure is proposed to predict the settlement and associated excess pore pressures of the soft Holocene clay deposits.
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Radial consolidation theories and numerical analysis of soft soil stabilisation via prefabricated vertical drains
2020Co-Authors: Buddhima Indraratna, Cholachat Rujikiatkamjorn, Rohan T WalkerAbstract:In this paper, an analytical solution based on actual radial soil permeability and compressibility is proposed considering the impact of parabolic variation of permeability in smear zone. The use of the spectral method for multilayered soil consolidation is introduced and verified. The Cavity Expansion Theory is employed to predict the extent of soil disturbance (smear zone) caused by the installation of mandrel driven vertical drains. The smear zone prediction is then compared to the data obtained from large-scale radial consolidation tests. Furthermore, the advantages and limitations of vacuum application through vertical drains are discussed using the proposed solutions. The applied vacuum pressure generates negative pore water pressure, resulting in an increase in effective stress within the soil, which leads to accelerated consolidation. Vacuum pressure is modelled as a distributed negative pressure (suction) along the drain length and across the soil surface. Analytical and numerical analyses incorporating the Authors’ equivalent plane strain solution are conducted to predict the excess pore pressures, lateral and vertical displacements. Application of the theoretical models for a selected case history is discussed and analysed, at the site of the 2nd Bangkok International Airport. The predictions are compared with the available field data, showing that an equivalent plane strain model can be used confidently to predict the performance with acceptable accuracy through rigorous mathematical modelling and numerical analysis. The research findings verify that the role of smear, drain unsaturation, and vacuum distribution can significantly affect the soil consolidation, hence, these aspects need to be modelled appropriately to obtain reliable predictions. INTRODUCTION Soft clay deposits usually have a low bearing capacity as well as excessive settlement characteristics. Therefore, it is necessary to improve the existing soft soils before commencing construction activities in order to prevent excessive and differential settlement (Richart, 1957). The application of vertical drains and preloading is a popular soil improvement technique. Vertical drains accelerate soil consolidation by providing short horizontal drainage paths for pore water flow, and are used worldwide in many soft soil improvement projects (Holtz et al., 1991; Indraratna et al., 1992; Indraratna and Redana, 2000). The utilisation of geosynthetic prefabricated vertical drains (PVDs) has become an economical and viable option because of their rapid installation with simple field equipment (Shang et al. 1998). In order to control the risk of embankment failure, Surcharge embankments are usually raised as a multi-stage exercise with rest periods provided between the loading stages (Jamiolkowski et al. 1983). This may not be possible with busy construction schedules. Application of vacuum load in addition to Surcharge Fill can further accelerate the rate of settlement to obtain the desired settlement without increasing the excess 1 Professor of Civil Engineering, Faculty of Engineering, University of Wollongong, Wollongong City, NSW 2522, Australia, E-mail: indra@uow.edu.au 2 Research Fellow, Faculty of Engineering, University of Wollongong, Wollongong City, NSW 2522, Australia 3 Research Associate, Faculty of Engineering, University of Wollongong, Wollongong City, NSW 2522, Australia pore pressure (Kjellman, 1952; Qian et al., 1992). This practice has been employed for land reclamation and port projects (Chu and Yan, 2005). The PVD system has also been employed to distribute vacuum pressure to deep subsoil layers, thereby increasing the consolidation rate. The consolidation process of the vacuum preloading in comparison with the conventional preloading is shown in Fig. (1).
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Performance of marine clay stabilised with vacuum pressure: Based on Queensland experience
Journal of rock mechanics and geotechnical engineering, 2019Co-Authors: Buddhima Indraratna, Cholachat Rujikiatkamjorn, Pankaj Baral, Jayantha AmeratungaAbstract:Abstract Stabilising soft marine clay and estuarine soils via vacuum preloading has become very popular in Australasia over the past decades because it is a cost-effective and time-efficient approach. In recent times, new land on areas outside but adjacent to existing port amenities, the Fisherman Islands at the Port of Brisbane (POB), was reclaimed to cater for an increase in trade activities. A vacuum preloading method combined with Surcharge to stabilise the deep layers of soil was used to enhance the application of prefabricated vertical drains (PVDs). This paper describes the performance of this combined Surcharge Fill and vacuum system under the embankment and also compares it with a Surcharge loading system to demonstrate the benefits of vacuum pressure over conventional Fill. The performance of this embankment is also presented in terms of field monitoring data, and the relative performance of the vacuum together with non-vacuum systems is evaluated. An analytical solution to radial consolidation with time-dependent Surcharge loading and vacuum pressure is also presented in order to predict the settlement and associated excess pore water pressure (EPWP) of deposits of thick soft clay.
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Monitoring of consolidation behaviour of marine clay treated with vacuum and Surcharge at the Port of Brisbane
Proceedings of the Ninth Symposium on Field Measurements in Geomechanics, 2015Co-Authors: Buddhima Indraratna, A S Balasubramaniam, Cholachat Rujikiatkamjorn, Jayantha Ameratunga, Harry G. Poulos, Darshana PereraAbstract:Over the past decade, the application of vacuum preloading for stabilising reclaimed soil and other low-lying estuarine soils has become popular in Australia. Its cost effectiveness is a governing factor in view of the reduced consolidation time to achieve a relatively high degree of consolidation. Due to demand in trade activities at the Port of Brisbane, new port facilities have been constructed on reclaimed land. A vacuum and Fill Surcharge, in conjunction with prefabricated vertical drains, was selected to accelerate consolidation time of the thick layers of subsoil. A performance comparison of a combined vacuum and Fill Surcharge loading system with a standard Surcharge Fill highlights the clear advantages of vacuum consolidation. Field data demonstrate how the embankment performed during construction. This paper also assesses the relative performance of the two contrasting preloading systems (i.e. vacuum and non-vacuum system).
A S Balasubramaniam - One of the best experts on this subject based on the ideXlab platform.
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Performance and prediction of marine clay treated with vacuum and Surcharge consolidation at Port of Brisbane
2020Co-Authors: Buddhima Indraratna, A S Balasubramaniam, Cholachat Rujikiatkamjorn, Harry G. Poulos, Jayantha AmeratungaAbstract:Over the past decade the application of vacuum preloading for stabilising soft offshore-coastal clay in shallow water and other low-lying estuarine soils has become popular in Australia. Its cost effectiveness is a major factor in most projects in view of the significantly reduced time for achieving a relatively high degree of consolidation. Due to an increase in trade activities at the Port of Brisbane, new facilities on Fisherman Islands at the mouth of the Brisbane River will be constructed on the new outer area (235ha) adjacent to the existing port facilities via land reclamation. A vacuum assisted Surcharge load and conventional Surcharge scheme, in conjunction with prefabricated vertical drains, was selected to reduce the required consolidation time through the deeper layers of subsoil. The performance of a combined vacuum and Surcharge Fill system and construction of the embankment are described in this paper. A comparison of the performance of a combined vacuum and Surcharge loading system with a standard Surcharge Fill highlights the clear benefits of vacuum consolidation. Field monitoring data are presented to demonstrate how the embankment performed during construction. This paper also evaluates the relative performance of the two contrasting preloading systems (i.e. vacuum and non-vacuum system). An analytical solution for radial consolidation that considers both time-dependent Surcharge loading and vacuum pressure is proposed to predict the settlement and associated excess pore pressures of the soft Holocene clay deposits.
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Monitoring of consolidation behaviour of marine clay treated with vacuum and Surcharge at the Port of Brisbane
Proceedings of the Ninth Symposium on Field Measurements in Geomechanics, 2015Co-Authors: Buddhima Indraratna, A S Balasubramaniam, Cholachat Rujikiatkamjorn, Jayantha Ameratunga, Harry G. Poulos, Darshana PereraAbstract:Over the past decade, the application of vacuum preloading for stabilising reclaimed soil and other low-lying estuarine soils has become popular in Australia. Its cost effectiveness is a governing factor in view of the reduced consolidation time to achieve a relatively high degree of consolidation. Due to demand in trade activities at the Port of Brisbane, new port facilities have been constructed on reclaimed land. A vacuum and Fill Surcharge, in conjunction with prefabricated vertical drains, was selected to accelerate consolidation time of the thick layers of subsoil. A performance comparison of a combined vacuum and Fill Surcharge loading system with a standard Surcharge Fill highlights the clear advantages of vacuum consolidation. Field data demonstrate how the embankment performed during construction. This paper also assesses the relative performance of the two contrasting preloading systems (i.e. vacuum and non-vacuum system).
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Consolidation of Estuarine Marine Clays for Coastal Reclamation Using Vacuum and Surcharge Loading
Geotechnical special publication, 2014Co-Authors: Buddhima Indraratna, Cholachat Rujikiatkamjorn, A S BalasubramaniamAbstract:Soft clays in coastal areas have low shear strength and high compressibility. Consequently, certain construction activities for infrastructure developments in these deposits often pose geotechnical problems due to large time-dependent settlements and lateral movements. Ground improvement techniques are adopted in such terrains to reduce the water content of soft clays by preloading with Surcharge Fill over vertical drains. Depending on the magnitude of the Surcharge load used, substantial immediate settlement with lateral movements can take place during preloading, leading to undrained stability problems in various parts of the clay foundation. Therefore, the use of vacuum-assisted preloading has now become a popular method in ground improvement works where substantial loads need to be carried out to meet a desired rate of settlement and mitigate undrained failure by controlling lateral displacements. To assist the vacuum propagation to significant depths, vertical drains are used in tandem at the Port of Brisbane, Australia, and vacuum-assisted Surcharge preloading and conventional Surcharge preloading schemes were adopted to reduce the consolidation time and long-term settlement in soft Holocene clays in 2009. It is shown that a combined vacuum Surcharge loading system with a standard Surcharge Fill highlights the obvious benefits of vacuum consolidation in reducing long-term settlement and enhanced stability.
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Ground improvement at the Port of Brisbane, Australia using vertical drains and vacuum assisted preloading
Geotechnical special publication, 2013Co-Authors: Buddhima Indraratna, Cholachat Rujikiatkamjorn, A S BalasubramaniamAbstract:Soft clays in coastal areas have low shear strength and high compressibility. Thus construction activities for infrastructure developments in these deposits often pose geotechnical problems due to large time dependent settlements and lateral movements. Ground improvement techniques are adopted to reduce the water content of the soft clays by preloading techniques with vertical drains. Depending on the magnitude of the Surcharge used substantial immediate settlement with lateral movements can takes place during preloading. This in turn causes stability problems in the loaded areas. The use of vacuum assisted preloading has now become a popular method in Australia where substantial loads need to be carried out to meet a desired rate of settlement and mitigate undrained failure. To assist the vacuum propagation to significant depths, vertical drains are used in conjunction. At the Port of Brisbane, Australia, vacuum assisted Surcharge preloading and conventional Surcharge preloading schemes were used to reduce the time required for consolidation and long term settlement in soft Holocene clays. The design of the combined vacuum and Surcharge Fill system and construction of the embankment are described in this paper. A comparison made on the performance of a combined vacuum Surcharge loading system with a standard Surcharge Fill highlights the clear benefits of vacuum consolidation. Field monitoring data on surface and sub-surface settlements, pore pressures and lateral movements on test embankments performed during construction are presented. An analytical solution for radial consolidation that considers both time-dependent Surcharge loading and vacuum pressure to predict the settlement and associated excess pore pressures in soft clay deposits is also proposed.
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Ground improvement at the port of Brisbane, Australia using vertical drains and vacuum assisted preloading
Geotechnical Special Publication, 2013Co-Authors: Buddhima Indraratna, Cholachat Rujikiatkamjorn, A S BalasubramaniamAbstract:Soft clays in coastal areas have low shear strength and high compressibility. Thus construction activities for infrastructure developments in these deposits often pose geotechnical problems due to large time dependent settlements and lateral movements. Ground improvement techniques are adopted to reduce the water content of the soft clays by preloading techniques with vertical drains. Depending on the magnitude of the Surcharge used substantial immediate settlement with lateral movements can takes place during preloading. This in turn causes stability problems in the loaded areas. The use of vacuum assisted preloading has now become a popular method in Australia where substantial loads need to be carried out to meet a desired rate of settlement and mitigate undrained failure. To assist the vacuum propagation to significant depths, vertical drains are used in conjunction. At the Port of Brisbane, Australia, vacuum assisted Surcharge preloading and conventional Surcharge preloading schemes were used to reduce the time required for consolidation and long term settlement in soft Holocene clays. The design of the combined vacuum and Surcharge Fill system and construction of the embankment are described in this paper. A comparison made on the performance of a combined vacuum Surcharge loading system with a standard Surcharge Fill highlights the clear benefits of vacuum consolidation. Field monitoring data on surface and sub-surface settlements, pore pressures and lateral movements on test embankments performed during construction are presented. An analytical solution for radial consolidation that considers both time-dependent Surcharge loading and vacuum pressure to predict the settlement and associated excess pore pressures in soft clay deposits is also proposed. © 2013 American Society of Civil Engineers.
M. W. Bo - One of the best experts on this subject based on the ideXlab platform.
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Factors affecting field settlement assessment and back-analysis by the asaoka and hyperbolic methods
2020Co-Authors: A. Arulrajah, Hamid Nikraz, M. W. BoAbstract:Thick deposits of marine clay are commonly present in coastal regions of the tropics. Land reclamation on this marine clay formation will require some form of ground treatment works to accelerate the consolidation process. The aim of ground treatment works is to negate settlements under the Fill load, future dead and live loads. The use of prefabricated vertical drains with a preloading option is the most widely used ground improvement method for the improvement of marine clays in land reclamation projects. After taking into account the submergence effect and settlement of the reclaimed land Surcharge of the equivalent working load is placed until the required degree of consolidation of the marine clay is obtained. As such, the assessment of the degree of consolidation of the marine clay is of paramount importance prior to the removal of the preload. The most suitable means of carrying out this assessment is by means of field settlement monitoring. During the process of consolidation, the field settlement monitoring data can be analysed by means of the Asaoka and hyperbolic methods to predict the ultimate settlement and the degree of consolidation of the underlying soft marine clay. There are various factors that affect the predictions by these methods such as the period of assessment after Surcharge placement and the time interval used for the assessment. The aim of the paper is to highlight the significance and impact of these factors on the field settlement assessment and the back-analysis of the coefficient of consolidation due to horizontal flow of soft clays and with special regard to coastal marine clays. Ground improvement works in the ongoing Changi East Reclamation Project in the Republic of Singapore comprises the installation of prefabricated vertical drains and the subsequent placement of sand Surcharge to accelerate the consolidation of the underlying soft marine clay. In such ground improvement projects in soft marine clay, the degree of improvement attained by the marine clay has to be ascertained to confirm whether the soil has achieved the required degree of consolidation to proceed with the Surcharge removal. This analysis can be carried out by means of observational methods for which continuous records of ground behaviour can be monitored from the date of field instrumentation installation. Field settlement monitoring data can be used to ascertain the settlement of the reclaimed Fill from the time of initial installation. The field settlement data can be analysed to predict the ultimate settlement of the reclaimed land under the Surcharge Fill. Back-analysis of the field settlement data will also enable the coefficient of consolidation due to horizontal flow to be closely estimated. A Pilot Testing Site was carried out at the reclamation project in the Republic of Singapore comprising of vertical drains installed in sub-areas at various spacings. Surcharge placement was carried out for a period of 32 months. The field settlement data of the various sub-areas was analysed to investigate the significance of the various factors that affect the prediction of the ultimate settlement, degree of consolidation and coefficient of consolidation due to horizontal flow by the Asaoka and Hyperbolic methods. The factors that affect the predictions by these methods are the period of assessment after Surcharge placement as well as the time interval used for the analysis. In this study, the degree of consolidation of the marine clay was analysed at assessment periods of 12, 24 and 32 months after Surcharge placement for both the Asaoka and Hyperbolic methods. For the Asaoka method, time intervals ranging from 7 to 56 days were adopted in the analysis to investigate the impact of the selected time intervals. The effect of factors such as these in the field settlement assessment and back-analysis of soft clay was initially described by Bo et al. (1999).
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Factors Affecting Consolidation Related Prediction of Singapore Marine Clay by Observational Methods
Geotechnical and Geological Engineering, 2008Co-Authors: A. Arulrajah, M. W. BoAbstract:The use of prefabricated vertical drains with preloading option is the most widely-used ground improvement method for the improvement of marine clays in land reclamation projects. The assessment of the degree of consolidation of the marine clay is of paramount importance prior to the removal of preload in such ground improvement projects. This analysis can be carried out by means of observational methods with the use of field settlement plates and piezometer monitoring. Field settlement monitoring data can be used to ascertain the settlement of the reclaimed Fill from the time of initial installation. The field settlement data can be analysed by the Asaoka method to predict the ultimate settlement of the reclaimed land under the Surcharge Fill. Back-analysis of the field settlement data will enable the coefficient of consolidation due to horizontal flow to be closely estimated. Piezometer monitoring data can be analysed to obtain the degree of consolidation of the improved marine clay. Back-analysis of the piezometer data will also enable the coefficient of consolidation due to horizontal flow to be estimated. The aim of this paper is to highlight the significance and impact of the various factors that affect prediction by the Asaoka and piezometer assessment methods. The authors findings of the Asaoka method reveal that the magnitude of ultimate settlement decreases and the degree of consolidation subsequently increases as a longer period of assessment is used in the prediction. The degree of consolidation predicted by the piezometers is found to be in good agreement with the Asaoka method for the early period of assessment. However as the assessment period increases, the piezometer indicates lower degree of consolidation as compared to field settlement predictions.
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Factors affecting field instrumentation assessment of marine clay treated with prefabricated vertical drains
Geotextiles and Geomembranes, 2004Co-Authors: A. Arulrajah, Hamid Nikraz, M. W. BoAbstract:Abstract The use of prefabricated vertical drains with preloading option is the most widely-used ground improvement method for the improvement of soft clays in land reclamation projects. Surcharge of equivalent working load after taking into account submergence effect and settlement of the reclaimed land is placed until the required degree of consolidation of the soft clay is obtained. The assessment of the degree of consolidation of the marine clay is of paramount importance prior to the removal of preload. This analysis can be carried out by means of observational methods with the use of field settlement plates and piezometer monitoring. Field settlement monitoring data can be used to ascertain the settlement of the reclaimed Fill from the time of initial installation. The field settlement data can be analysed by the Asaoka and Hyperbolic methods to predict the ultimate settlement of the reclaimed land under the Surcharge Fill. Back-analysis of the field settlement data by the Asaoka method will enable the coefficient of consolidation due to horizontal flow to be closely estimated. Piezometer monitoring data can be analysed to obtain the degree of consolidation of the improved marine clay. Back-analysis of the piezometer data will also enable the coefficient of consolidation due to horizontal flow to be estimated. The authors’ findings of the Asaoka method reveal that the magnitude of ultimate settlement decreases and the degree of consolidation subsequently increases as a longer period of assessment is used in the prediction. It is apparent that as the time interval increases, a cut-off time interval is obtained after which increasing time intervals would converge to the same magnitude of ultimate settlement. The authors’ findings of the Hyperbolic method reveal that the magnitude of ultimate settlement increases and subsequently the degree of consolidation decreases as a longer period of assessment is used in the prediction. The degree of consolidation predicted by the piezometers is found to be in good agreement with the Asaoka and Hyperbolic methods for the early period of assessment. However as the assessment period increases, the piezometer indicates lower degree of consolidation as compared to field settlement predictions. The aim of this paper is to highlight the significance and influence of various factors that affect predictions by the Asaoka, Hyperbolic and piezometer assessment methods.
Robert D Holtz - One of the best experts on this subject based on the ideXlab platform.
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Geosynthetic Reinforced Wall Analysis Phase II: Use of In-Soil Geosynthetic Behavior to Predict Deformations, Volume 1: Research Program and Results
1998Co-Authors: Robert D HoltzAbstract:As part of the reconstruction of Interstate 90 in Seattle, Washington, the Washington State Department of Transportation (WSDOT) designed and supervised the construction of a geosynthetic reinforced soil (GRS) retaining wall located on Rainier Avenue, Seattle. The Rainier Avenue wall had a maximum height of 12.6 m and supported a nearly 6-m-high Surcharge Fill. At the time it was constructed, it was the highest GRS wall in the world. The wall was extensively instrumented and monitored during and after construction to evaluate its face deflections and the strain levels occurring in it. To define the actual stress distribution occurring in the Rainier Avenue wall, a two-phase research project was conducted by the University of Washington. Phase I included an extensive laboratory test program that used a newly developed plane strain device. Numerical analysis and modeling of the results of the instrumentation and laboratory tests constituted Phase II. The major tasks of the Phase II project were to (1) analyze the test result of the unit cell device (UCD), a plane strain GRS element testing device developed in Phase I; (2) develop numerical models of the Rainier Avenue wall using both material properties and test results of the UCD; and (3) using the results of tasks 1 and 2, develop a methodology for analyzing the working stress-strain distribution in the GRS retaining structures. The Phase II project was conducted from September 1995 to December 1997. During this period, two research programs were conducted simultaneously. One program concentrated on analyzing the UCD test results, and the other on developing the numerical models of the Rainier Avenue wall. Significant results were obtained from both research programs. Products of the Phase II research include an elasticity model that is capable of analyzing GRS behavior, composite properties of GRS elements, and four numerical models of the Rainier Avenue wall. Improved understanding of the working stress-strain distribution inside GRS retaining structures was also obtained with these products.
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Geosynthetic Reinforced Wall Analysis Phase II: Use of In-Soil Geosynthetic Behavior to Predict Deformations, Volume 2: Implementation—Computer Codes and Files
1998Co-Authors: Robert D HoltzAbstract:As part of the reconstruction of Interstate 90 in Seattle, Washington, the Washington State Department of Transportation (WSDOT) designed and supervised the construction of a geosynthetic reinforced soil (GRS) retaining wall located on Rainier Avenue, Seattle. The Rainier Avenue wall had a maximum height of 12.6 m and supported a nearly 6-m-high Surcharge Fill. At the time it was constructed, it was the highest GRS wall in the world. The wall was extensively instrumented and monitored during and after construction to evaluate its face deflections and the strain levels occurring in it. To define the actual stress distribution occurring in the Rainier Avenue wall, a two-phase research project was conducted by the University of Washington. Phase I included an extensive laboratory test program that used a newly developed plane strain device. Numerical analysis and modeling of the results of the instrumentation and laboratory tests constituted Phase II. The major tasks of the Phase II project were to (1) analyze the test result of the unit cell device (UCD), a plane strain GRS element testing device developed in Phase I; (2) develop numerical models of the Rainier Avenue wall using both material properties and test results of the UCD; and (3) using the results of tasks 1 and 2, develop a methodology for analyzing the working stress-strain distribution in the GRS retaining structures. The Phase II project was conducted from September 1995 to December 1997. During this period, two research programs were conducted simultaneously. One program concentrated on analyzing the UCD test results, and the other on developing the numerical models of the Rainier Avenue wall. Significant results were obtained from both research programs. Products of the Phase II research include an elasticity model that is capable of analyzing GRS behavior, composite properties of GRS elements, and four numerical models of the Rainier Avenue wall. Improved understanding of the working stress-strain distribution inside GRS retaining structures was also obtained with these products.