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Dennis T. Bergado - One of the best experts on this subject based on the ideXlab platform.

  • prefabricated vertical drain pvd and deep cement mixing dcm stiffened dcm sdcm techniques for soft ground improvement
    IOP Conference Series: Earth and Environmental Science, 2018
    Co-Authors: Dennis T. Bergado, P V Long, Salisa Chaiyaput, Aramugam Balasubramaniam
    Abstract:

    Soft ground improvement techniques have become most practical and popular methods to increase soil strength, soil stiffness and reduce soil compressibility including the soft Bangkok clay. This paper focuses on comparative performances of prefabricated vertical drain (PVD) using surcharge, vacuum and heat preloading as well as the cement-admixed clay of Deep Cement Mixing (DCM) and Stiffened DCM (SDCM) methods. The Vacuum-PVD can increase the Horizontal Coefficient of consolidation, Ch, resulting in faster rate of settlement at the same magnitudes of settlement compared to Conventional PVD. Several field methods of applying vacuum preloading are also compared. Moreover, the Thermal PVD and Thermal Vacuum PVD can increase further the Coefficient of Horizontal consolidation, Ch, with the associated reduction of kh/ks values by reducing the drainage retardation effects in the smear zone around the PVD which resulted in faster rates of consolidation and higher magnitudes of settlements. Furthermore, the equivalent smear effect due to non-uniform consolidation is also discussed in addition to the smear due to the mechanical installation of PVDs. In addition, a new kind of reinforced deep mixing method, namely Stiffened Deep Cement Mixing (SDCM) pile is introduced to improve the flexural resistance, improve the field quality control, and prevent unexpected failures of the Deep Cement Mixing (DCM) pile. The SDCM pile consists of DCM pile reinforced with the insertion of precast reinforced concrete (RC) core. The full scale test embankment on soft clay improved by SDCM and DCM piles was also analysed. Numerical simulations using the 3D PLAXIS Foundation finite element software have been done to understand the behavior of SDCM and DCM piles. The simulation results indicated that the surface settlements decreased with increasing lengths of the RC cores, and, at lesser extent, increasing sectional areas of the RC cores in the SDCM piles. In addition, the lateral movements decreased by increasing the lengths (longer than 4 m) and, the sectional areas of the RC cores in the SDCM piles. The results of the numerical simulations closely agreed with the observed data and successfully verified the parameters affecting the performances and behavior of both SDCM and DCM piles.

  • PVD improvement of soft Bangkok clay with and without vacuum preloading using analytical and numerical analyses
    Geotextiles and Geomembranes, 2015
    Co-Authors: Le Gia Lam, Dennis T. Bergado, Takenori Hino
    Abstract:

    Abstract This paper presents the performance of improved soft Bangkok clay with prefabricated vertical drains (PVDs) combined with embankment preloading (conventional PVD method) and vacuum preloading (vacuum PVD method). The performance was evaluated in terms of settlements and flow parameters using analytical methods and numerical simulations in the ABAQUS software. The Horizontal Coefficient of consolidation (Ch), the ratio (kh/ks) between the Horizontal hydraulic conductivity in the undisturbed zone (kh) and the Horizontal hydraulic conductivity in the smeared zone (ks), and the final settlement (Sf) were back-calculated using the measured data. The sensitivity analysis was performed by varying the values of kh/ks. The vacuum PVD method was confirmed to have a higher rate of settlement than the conventional method. In particular, Ch increased from 4Cv to 5Cv, kh/ks decreased from 8 to 7, and the consolidation time required to obtain a settlement of 1.30 m decreased from 300 days to 100 days. In addition, the calculated results from both the analytical method and FEM simulations for the conventional PVD agreed with the measured data. However, the results from the vacuum PVD method demonstrated that the FEM simulations yielded more reasonable results compared with the corresponding results obtained from the analytical methods.

  • Back-analyses of flow parameters of PVD improved soft Bangkok clay with and without vacuum preloading from settlement data and numerical simulations
    Geotextiles and Geomembranes, 2014
    Co-Authors: P Voottipruex, Dennis T. Bergado, L.g. Lam, Takenori Hino
    Abstract:

    Abstract Prefabricated vertical drains (PVDs) with embankment preloading (conventional PVDs) and with embankment combined with vacuum preloading (Vacuum-PVDs) are examined using the field data obtained from the site of the Suvarnabhumi Airport, Thailand. The flow parameters were back-analyzed by comparison of measured and predicted or simulated data. The flow parameters were illustrated in terms of the Horizontal Coefficient of consolidation (Ch) and the ratio between the Horizontal hydraulic conductivity in undisturbed zone (kh) and the Horizontal hydraulic conductivity in smear zone (ks) or (kh/ks). Numerical simulations using one-dimensional FEM PVDCON software with equivalent vertical permeability, kev, to determine the appropriate Ch and kh/ks of PVDs with conventional embankment preloading and with embankment combined with vacuum preloading schemes were made. Furthermore, numerical simulations using axisymmetric FEM by ABAQUS software, incorporating Horizontal (kh) and vertical (kv) permeabilities, to determine the appropriate kh/ks based on back-calculated Ch of conventional PVD and Vacuum-PVD schemes were also done. The Vacuum-PVD scheme indicated faster rate of settlement than conventional PVD scheme by about 1.7–1.8 times with slight reduction of the kh/ks ratios. For conventional PVD, it was demonstrated that the increase in kh/ks ratios reduced the simulated rate of settlement.

  • Recent Developments of PVD Soft Ground Improvement: Laboratory Test Results and Simulations
    Geotechnical Predictions and Practice in Dealing with Geohazards, 2013
    Co-Authors: Dennis T. Bergado, J Saowapakpiboon, S Artidteang, Yip Poon Lai
    Abstract:

    This chapter focuses on the recent developments of soft ground improvement using prefabricated vertical drain (PVD) combined with surcharge, vacuum, and heat preloading in shortening the consolidation time. The laboratory tests were conducted in a large-scale consolidometer with reconstituted specimens using PVD combined with surcharge (PVD only); PVD combined with surcharge and vacuum pressure (Vacuum-PVD); PVD combined with surcharge and heat up to 90 °C (Thermo-PVD); and PVD combined with surcharge, vacuum pressure, and heat up to 90 °C (Thermo-Vacuum-PVD). Analyses were carried out to determine the flow parameters by back-calculation in terms of the Horizontal Coefficient of consolidation (C h) and the ratio between the Horizontal permeability in the undisturbed zone (K h) to the Horizontal permeability in the smear zone (K s) or (K h /K s). The C h values for reconstituted specimens with PVD, Vacuum-PVD, Thermo-PVD, and Thermo-Vacuum-PVD were 1.93 m2/year, 2.23 m2/year, 4.17 m2/year, and 4.38 m2/year, respectively, with corresponding K h /K s values of 3.0, 2.7, 1.4, and 1.1, respectively. The results of FEM numerical simulations using ABAQUS software yielded good agreement with the measured settlements and excess pore water pressures. Moreover, the higher temperatures resulted in reduced viscosity of water, which resulted in the increase in the Horizontal permeability. The Thermo-PVD and Thermo-Vacuum-PVD resulted in faster rates of consolidation and higher magnitudes of settlement because of the reduction of the drainage retardation effects in the smear zone surrounding the PVD, which resulted in the reduction of K h /K s and increased Coefficient of Horizontal consolidation, C h.

  • comparison on the performance of prefabricated vertical drain pvd preloading combined with and without vacuum and heat
    Lowland technology international : the official journal of the International Association of Lowland Technology, 2011
    Co-Authors: J Saowapakpiboon, Dennis T. Bergado, S Artidteang
    Abstract:

    This paper focus on performance of prefabricated vertical drain (PVD) preloading combined with and without vacuum and heat to accelerate the consolidation of soft Bangkok clay. The laboratory tests were conducted using reconstituted specimens in large scale consolidometers combined with and without vacuum and heat. The flow parameters were back calculated in terms of the Horizontal Coefficient of consolidation (Ch) and the ratio between the Horizontal permeability in undisturbed zone (kh) to the Horizontal permeability in smear zone (ks) or (kh/ks) based on Hansbo (1979) method. The back-calculation analysis results show that the combination of vacuum pressure and heat can increase the Horizontal Coefficient of consolidation, Ch of 126.42% and decrease of kh/ks of 63.33%. Furthermore, vacuum can increase higher rate of consolidation temperature can decrease viscosity of pore water by reducing the drainage retardation effects in the smear zone around the PVD which resulted in faster rate of consolidation and higher magnitude of settlement.

Changxin Shi - One of the best experts on this subject based on the ideXlab platform.

  • effect of surcharge loading rate and mobilized load ratio on the performance of vacuum surcharge preloading with pvds
    Geotextiles and Geomembranes, 2019
    Co-Authors: Jun Wang, Ziyang Gao, Guangya Ding, Yuanqiang Cai, Xueyu Geng, Changxin Shi
    Abstract:

    Abstract The results from three laboratory model tests performed under various vacuum and surcharge loads with PVDs are reported. Different SLRs were adopted to investigate the effect on the consolidation of dredged soil. To measure the lateral displacement, a refitted inclinometer was developed and tested. In the tests, the settlement, lateral displacement, and vane shear strength were measured, and the degree of consolidation (DOC), Horizontal Coefficient of consolidation (Ch), and bearing capacity were calculated. The results indicate that larger SLR values promote consolidation. The largest vane shear strength, settlement, and Ch values were all obtained under the highest SLR, and the bearing capacity under this SLR was more than double that under the lowest SLR. The DOC was found to increase with the growth of the SLR. However, considering the vacuum pressure was higher in Case-III, the influence of SLR on reinforcement effect may not be so significant.

  • Effect of surcharge loading rate and mobilized load ratio on the performance of vacuum–surcharge preloading with PVDs
    Geotextiles and Geomembranes, 2019
    Co-Authors: Jun Wang, Ziyang Gao, Guangya Ding, Yuanqiang Cai, Xueyu Geng, Changxin Shi
    Abstract:

    Abstract The results from three laboratory model tests performed under various vacuum and surcharge loads with PVDs are reported. Different SLRs were adopted to investigate the effect on the consolidation of dredged soil. To measure the lateral displacement, a refitted inclinometer was developed and tested. In the tests, the settlement, lateral displacement, and vane shear strength were measured, and the degree of consolidation (DOC), Horizontal Coefficient of consolidation (Ch), and bearing capacity were calculated. The results indicate that larger SLR values promote consolidation. The largest vane shear strength, settlement, and Ch values were all obtained under the highest SLR, and the bearing capacity under this SLR was more than double that under the lowest SLR. The DOC was found to increase with the growth of the SLR. However, considering the vacuum pressure was higher in Case-III, the influence of SLR on reinforcement effect may not be so significant.

P Voottipruex - One of the best experts on this subject based on the ideXlab platform.

  • Back-analyses of flow parameters of PVD improved soft Bangkok clay with and without vacuum preloading from settlement data and numerical simulations
    Geotextiles and Geomembranes, 2014
    Co-Authors: P Voottipruex, Dennis T. Bergado, L.g. Lam, Takenori Hino
    Abstract:

    Abstract Prefabricated vertical drains (PVDs) with embankment preloading (conventional PVDs) and with embankment combined with vacuum preloading (Vacuum-PVDs) are examined using the field data obtained from the site of the Suvarnabhumi Airport, Thailand. The flow parameters were back-analyzed by comparison of measured and predicted or simulated data. The flow parameters were illustrated in terms of the Horizontal Coefficient of consolidation (Ch) and the ratio between the Horizontal hydraulic conductivity in undisturbed zone (kh) and the Horizontal hydraulic conductivity in smear zone (ks) or (kh/ks). Numerical simulations using one-dimensional FEM PVDCON software with equivalent vertical permeability, kev, to determine the appropriate Ch and kh/ks of PVDs with conventional embankment preloading and with embankment combined with vacuum preloading schemes were made. Furthermore, numerical simulations using axisymmetric FEM by ABAQUS software, incorporating Horizontal (kh) and vertical (kv) permeabilities, to determine the appropriate kh/ks based on back-calculated Ch of conventional PVD and Vacuum-PVD schemes were also done. The Vacuum-PVD scheme indicated faster rate of settlement than conventional PVD scheme by about 1.7–1.8 times with slight reduction of the kh/ks ratios. For conventional PVD, it was demonstrated that the increase in kh/ks ratios reduced the simulated rate of settlement.

  • Soft ground improvement with solar-powered drainage
    Proceedings of the Institution of Civil Engineers - Ground Improvement, 2010
    Co-Authors: Chanidnun Pothiraksanon, J Saowapakpiboon, P Voottipruex, Dennis T. Bergado, Hossam Medhat Abuel-naga
    Abstract:

    In this study, raising the temperature of soft Bangkok clay up to 90°C using solar-powered prefabricated vertical drains during a preloading process was investigated in full-scale field tests. Two identical 6 m high, full-scale test embankments for preloading were constructed over the soft Bangkok clay where a conventional vertical drainage system was installed underneath one embankment and a solar-powered system was utilised for the other. Analyses were carried out to determine the flow parameters by back-calculation of field settlements in terms of the Horizontal Coefficient of consolidation (Ch) and the ratio between the Horizontal hydraulic conductivity in the undisturbed zone (Kh) to the Horizontal hydraulic conductivity in the smear zone (Ks). The field test analysis based upon the back-calculated results shows that the Kh/Ks values were 6·2 and 4·1 for drainage without and with heat, respectively, with corresponding Ch values of 6·8 and 8·5 m2/year, respectively. Thus, the use of solar heating can ...

  • Measured and predicted performance of prefabricated vertical drains (PVDs) with and without vacuum preloading
    Geotextiles and Geomembranes, 2010
    Co-Authors: J Saowapakpiboon, Dennis T. Bergado, Sompote Youwai, Jinchun Chai, P. Wanthong, P Voottipruex
    Abstract:

    Abstract This paper presents the effectiveness of vacuum preloading in accelerating the consolidation of PVD improved soft Bangkok clay by comparing with the corresponding results without vacuum preloading. Laboratory tests were conducted using a large scale consolidometer having diameter of 300 mm and height of 500 mm with reconstituted specimens installed with prefabricated vertical drains (PVD) with and without vacuum preloading. In addition, field data were collected from Second Bangkok International Airport (SBIA) site improved by PVD with and without vacuum pressures. Analyses were carried out to compare the compressibility parameters ( C h and k h / k s ) by back-calculation of laboratory and field settlements using Hansbo (1979) method. From the laboratory tests, the Horizontal Coefficient of consolidation ( C h ) values from reconstituted specimens were 1.08 and 1.87 m 2 /yr for PVD without and with vacuum pressure, respectively and the k h / k s values were 2.7 for PVD only and 2.5 for vacuum-PVD. After the improvement, the water contents of the soft clay were reduced, thereby, increasing its undrained shear strengths. Similarly, the field data analysis based on the back-calculated results showed that the k h / k s were 7.2 and 6.6 for PVD without and with vacuum, respectively. The C h values increased slightly from 2.17 m 2 /yr for PVD only to 3.51 m 2 /yr for vacuum-PVD. The time to reach 90% degree of consolidation for soils with vacuum-PVD was one-third shorter than that for soils with PVD only because of higher C h values. Thus, the addition of vacuum pressure leads to increase Horizontal Coefficient of consolidation which shortened the time of preloading. The PVDCON software was found to be useful to predict the settlements of the PVD improved ground with and without vacuum preloading.

  • assessing the performance of prefabricated vertical drain with vacuum and heat preloading
    Geosynthetics International, 2009
    Co-Authors: J Saowapakpiboon, Y M Thann, Dennis T. Bergado, P Voottipruex
    Abstract:

    ABSTRACT: This paper presents the effects of vacuum and heat preloading of a prefabricated vertical drains (PVD) that are used to accelerate consolidation of soft Bangkok clay. Laboratory model tests were conducted in small-scale consolidometers with undisturbed and reconstituted specimens of untreated (PVD), vacuum-treated (vacuum-PVD) and temperature treated (thermo-PVD) materials. The flow parameters were back-calculated using the Hansbo (Ground Engineering, 12, No. 5, 16–25, 1979) method in terms of the Horizontal Coefficient of consolidation (Ch) and the ratio of the Horizontal hydraulic conductivity in the undisturbed zone (Kh) to the Horizontal hydraulic conductivity in the smear zone (Ks) or (Kh/Ks). From the results of the laboratory tests, the increased hydraulic conductivity of the smear zone of undisturbed specimens using vacuum-PVD and thermo-PVD resulted in a decrease in Kh/Ks of about 11 and 12%, and an increase in Ch of 2 and 13%, respectively. On the other hand, the increased hydraulic co...

Yuanqiang Cai - One of the best experts on this subject based on the ideXlab platform.

  • effect of surcharge loading rate and mobilized load ratio on the performance of vacuum surcharge preloading with pvds
    Geotextiles and Geomembranes, 2019
    Co-Authors: Jun Wang, Ziyang Gao, Guangya Ding, Yuanqiang Cai, Xueyu Geng, Changxin Shi
    Abstract:

    Abstract The results from three laboratory model tests performed under various vacuum and surcharge loads with PVDs are reported. Different SLRs were adopted to investigate the effect on the consolidation of dredged soil. To measure the lateral displacement, a refitted inclinometer was developed and tested. In the tests, the settlement, lateral displacement, and vane shear strength were measured, and the degree of consolidation (DOC), Horizontal Coefficient of consolidation (Ch), and bearing capacity were calculated. The results indicate that larger SLR values promote consolidation. The largest vane shear strength, settlement, and Ch values were all obtained under the highest SLR, and the bearing capacity under this SLR was more than double that under the lowest SLR. The DOC was found to increase with the growth of the SLR. However, considering the vacuum pressure was higher in Case-III, the influence of SLR on reinforcement effect may not be so significant.

  • Effect of surcharge loading rate and mobilized load ratio on the performance of vacuum–surcharge preloading with PVDs
    Geotextiles and Geomembranes, 2019
    Co-Authors: Jun Wang, Ziyang Gao, Guangya Ding, Yuanqiang Cai, Xueyu Geng, Changxin Shi
    Abstract:

    Abstract The results from three laboratory model tests performed under various vacuum and surcharge loads with PVDs are reported. Different SLRs were adopted to investigate the effect on the consolidation of dredged soil. To measure the lateral displacement, a refitted inclinometer was developed and tested. In the tests, the settlement, lateral displacement, and vane shear strength were measured, and the degree of consolidation (DOC), Horizontal Coefficient of consolidation (Ch), and bearing capacity were calculated. The results indicate that larger SLR values promote consolidation. The largest vane shear strength, settlement, and Ch values were all obtained under the highest SLR, and the bearing capacity under this SLR was more than double that under the lowest SLR. The DOC was found to increase with the growth of the SLR. However, considering the vacuum pressure was higher in Case-III, the influence of SLR on reinforcement effect may not be so significant.

Takenori Hino - One of the best experts on this subject based on the ideXlab platform.

  • PVD improvement of soft Bangkok clay with and without vacuum preloading using analytical and numerical analyses
    Geotextiles and Geomembranes, 2015
    Co-Authors: Le Gia Lam, Dennis T. Bergado, Takenori Hino
    Abstract:

    Abstract This paper presents the performance of improved soft Bangkok clay with prefabricated vertical drains (PVDs) combined with embankment preloading (conventional PVD method) and vacuum preloading (vacuum PVD method). The performance was evaluated in terms of settlements and flow parameters using analytical methods and numerical simulations in the ABAQUS software. The Horizontal Coefficient of consolidation (Ch), the ratio (kh/ks) between the Horizontal hydraulic conductivity in the undisturbed zone (kh) and the Horizontal hydraulic conductivity in the smeared zone (ks), and the final settlement (Sf) were back-calculated using the measured data. The sensitivity analysis was performed by varying the values of kh/ks. The vacuum PVD method was confirmed to have a higher rate of settlement than the conventional method. In particular, Ch increased from 4Cv to 5Cv, kh/ks decreased from 8 to 7, and the consolidation time required to obtain a settlement of 1.30 m decreased from 300 days to 100 days. In addition, the calculated results from both the analytical method and FEM simulations for the conventional PVD agreed with the measured data. However, the results from the vacuum PVD method demonstrated that the FEM simulations yielded more reasonable results compared with the corresponding results obtained from the analytical methods.

  • Back-analyses of flow parameters of PVD improved soft Bangkok clay with and without vacuum preloading from settlement data and numerical simulations
    Geotextiles and Geomembranes, 2014
    Co-Authors: P Voottipruex, Dennis T. Bergado, L.g. Lam, Takenori Hino
    Abstract:

    Abstract Prefabricated vertical drains (PVDs) with embankment preloading (conventional PVDs) and with embankment combined with vacuum preloading (Vacuum-PVDs) are examined using the field data obtained from the site of the Suvarnabhumi Airport, Thailand. The flow parameters were back-analyzed by comparison of measured and predicted or simulated data. The flow parameters were illustrated in terms of the Horizontal Coefficient of consolidation (Ch) and the ratio between the Horizontal hydraulic conductivity in undisturbed zone (kh) and the Horizontal hydraulic conductivity in smear zone (ks) or (kh/ks). Numerical simulations using one-dimensional FEM PVDCON software with equivalent vertical permeability, kev, to determine the appropriate Ch and kh/ks of PVDs with conventional embankment preloading and with embankment combined with vacuum preloading schemes were made. Furthermore, numerical simulations using axisymmetric FEM by ABAQUS software, incorporating Horizontal (kh) and vertical (kv) permeabilities, to determine the appropriate kh/ks based on back-calculated Ch of conventional PVD and Vacuum-PVD schemes were also done. The Vacuum-PVD scheme indicated faster rate of settlement than conventional PVD scheme by about 1.7–1.8 times with slight reduction of the kh/ks ratios. For conventional PVD, it was demonstrated that the increase in kh/ks ratios reduced the simulated rate of settlement.