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P. Severi - One of the best experts on this subject based on the ideXlab platform.
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Hydrologic control on natural land subsidence in the shallow coastal aquifer of the Ravenna coast, Italy
Proceedings of the International Association of Hydrological Sciences, 2020Co-Authors: Marco Antonellini, Beatrice Maria Sole Giambastiani, Nicolas Greggio, L. Bonzi, Lorenzo Calabrese, Paolo Luciani, Luisa Perini, P. SeveriAbstract:Abstract. Multiple processes contributing to natural land subsidence in a shallow coastal aquifer near Ravenna (Italy) were identified by analysing the relationships among different data set time series (water table level, rainfall, land reclamation drainage, sea level, etc.) and establishing the correlations with vertical ground motion observed at a high-resolution settlement gauge. Our study highlights the presence of three deformation components related to different processes controlling land subsidence: elastic, delayed-elastic, and irreversible (plastic) components. The elastic and delayed-elastic components are closely related to water table fluctuations that change the effective stress in two portions of the coastal aquifer at a daily (in the sandy unconfined portion) and seasonal time scales (in the layered clay-rich semi-confined prodelta portion), respectively. The irreversible component represents the trend in the land subsidence time series and is due to Primary Consolidation (pore pressure dissipation) of the fine-grained prodelta levels above where the settlement gauge is located. The amplitudes of the elastic component can be up to 0.2–0.3 mm whereas the amplitude of the delayed-elastic component reaches 0.89 mm. The Primary Consolidation rate of deformation is 0.9 mm yr −1 and constrains the likely age of prodelta sediments deposition to 1300–2800 years before present. The delayed-elastic subsidence rate has similar magnitude to that due to Primary Consolidation and is connected to poroelastic effects in the prodelta sequence following seasonal variations in water table. Our findings are important for planning land subsidence management and monitoring strategies especially where the surface aquifer structure is heterogeneous due to different depositional settings. The natural land subsidence rate in the Holocene sediments of the shallow coastal aquifer of Ravenna (North eastern Italy) that we measured in this study accounts for 10 %–20 % of the total current land subsidence rate observed in this portion of Ravenna coastal area (10–20 mm yr −1 ).
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Processes governing natural land subsidence in the shallow coastal aquifer of the Ravenna coast, Italy
CATENA, 2019Co-Authors: Marco Antonellini, Beatrice Maria Sole Giambastiani, Nicolas Greggio, L. Bonzi, Lorenzo Calabrese, Paolo Luciani, Luisa Perini, P. SeveriAbstract:Abstract We identified the processes governing natural land subsidence in a shallow coastal aquifer near Ravenna (North eastern Italy) by analysing the relationships among different data set time series (water table level, rainfall, drainage, sea level, etc.) and establishing the correlations with vertical ground motion observed at a high-resolution settlement gauge. For the first time we establish the relationships between water table fluctuations and vertical displacement in a real field dataset as well as demonstrate the important contribution of Primary Consolidation and aquifer stratigraphy to natural land subsidence. Our study highlights the presence of three deformation components related to different processes controlling land subsidence: elastic, delayed-elastic, and irreversible (plastic) components. The elastic and delayed-elastic components are closely related to water table fluctuations that change the effective stress in two portions of the coastal aquifer at a daily (in the sandy unconfined portion) and seasonal time scales (in the finely layered clay-rich semiconfined prodelta portion), respectively. The irreversible component represents the trend in the land subsidence time series and is due to Primary Consolidation (pore water pressure dissipation) of the fine-grained prodelta levels above where the settlement gauge is located. The amplitudes of the elastic component can be up to 0.2–0.3 mm whereas the amplitude of the delayed-elastic component reaches 0.89 mm. The Primary Consolidation rate of deformation is 0.9 mm/year and constrains the likely age of prodelta sediments deposition to 1300–2800 years before present. The average degree of Consolidation for the prodelta sediments varies from 0.8 to 0.99 according to Consolidation coefficients varying from 1.58 to 3.15 m2/year, which are accepted values in the literature. Our analysis point out that Primary Consolidation in the shallow fine-grained sediments of the shallow coastal aquifer is still ongoing. The delayed-elastic land subsidence rate has similar magnitude to that due to Primary Consolidation and is likely connected to poroelastic effects in the prodelta sequence following seasonal variations in water table. Our findings are important for planning land subsidence management and monitoring strategies especially where the surface aquifer structure is heterogeneous due to different depositional settings.
Hueiwen Chang - One of the best experts on this subject based on the ideXlab platform.
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Long-term settlement behavior of soft grounds and secondary compression
Journal of the Chinese Institute of Engineers, 2017Co-Authors: Yoshihito Imai, Masaru Akaishi, Wen-chao Huang, Hueiwen ChangAbstract:AbstractSettlement–time behaviors in the last stage of Consolidation are studied both in the laboratory and in the field. It is shown that the long-term settlement–time curves observed in the field are linear with the logarithm of time and the rate of the long-term settlement are analogous to the rate of secondary compression measured in a laboratory. The finite difference Consolidation analyses for cohesive soils exhibiting large amounts of secondary compression during Primary Consolidation provide fairly good predictions of the settlement–time curves observed in the laboratory and in the field. In this paper, the applicability of the secondary compression model established in the laboratory is examined in in situ conditions. The initial rate of secondary compression used in this paper has a predominant influence on the settlement–time curve with different drainage distances. It is emphasized that the assumption for unknown secondary compression behaviors during the Primary Consolidation has a predominan...
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secondary compression behavior in one dimensional Consolidation tests
Journal of GeoEngineering, 2012Co-Authors: Toshihiko Takeda, Motohiro Sugiyama, Masaru Akaishi, Hueiwen ChangAbstract:One-dimensional Consolidation analysis is described for predicting the Consolidation time curves of clay exhibiting secondary compression during Primary Consolidation. The constitutive soil model is based on the equation governing the secondary compression rate of the decrease in void ratio. This model uses four parameters, namely, Cc, * c C , Cα and * v c , that can be easily determined or assumed from incremental loading (IL) oedometric Consolidation tests. In order to be certain of the correct proposed soil model, the Consolidation time curves observed in oedometer specimens are compared against those predicted by the analysis. A satisfactory agreement between the computed behaviors and oedometer observations would indicate the correct assumption. In addition, it is shown that the void ratio rate ( s e�) due to secondary compression during Primary Consolidation varies by approximately 10 2~3 times as much as its final value before the application of the next loading increment.
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initial rates of secondary compression in one dimensional Consolidation analysis
Proceedings of the School of Engineering of Tokai University, 2010Co-Authors: Toshihiko Takeda, Motohiro Sugiyama, Masaru Akaishi, Hueiwen ChangAbstract:The finite difference analysis of one-dimensional Consolidation of clays, exhibiting large amounts of secondary compression during Primary Consolidation, provide fairly good predictions of the Consolidation-time curve for oedometer specimens with different heights. Some parameters including the initial rate of secondary compression defined by Primary Consolidation in this analysis have been assumed to avoid experimental difficulty. The trial and error calculation procedure was therefore used where the calculated Consolidation-time curves fit the observed ones. Finally, it is emphasized that the assumption for unknown secondary compression behaviors during Primary Consolidation has a predominant influence on the Consolidation-time curve.
Zhen-shun Hong - One of the best experts on this subject based on the ideXlab platform.
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On the volumetric strain-time curve patterns of dredged clays during Primary Consolidation
Géotechnique, 2015Co-Authors: Ling-ling Zeng, Zhen-shun Hong, Yu-jun CuiAbstract:Thirteen one-dimensional Consolidation tests with step loading were performed on dredged clays reconstituted at different initial water contents. Both vertical deformation and pore pressure were measured during Primary Consolidation, which refers to the time-dependent compression process associated with the dissipation of pore pressure. The pore pressure changes were investigated by considering the maximum and the residual values. The development of compression during pore pressure dissipation was analysed to identify the change patterns in volumetric strain-time curves. Three types of change patterns were found during the Primary Consolidation, and the remoulded yield stress was found to be the key factor in classifying the change patterns. The inflexion point is absent for types 1 and 2, indicating that the end of Primary Consolidation cannot be determined by the commonly used Taylor and Casagrande methods. Type 3 shows an inverse 'S' shape, suggesting that the end of Primary Consolidation determined based on the compression-time curves occurs before the completion of pore pressure dissipation.
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on the volumetric strain time curve patterns of dredged clays during Primary Consolidation
Geotechnique, 2015Co-Authors: Ling-ling Zeng, Zhen-shun Hong, Yu-jun CuiAbstract:Thirteen one-dimensional Consolidation tests with step loading were performed on dredged clays reconstituted at different initial water contents. Both vertical deformation and pore pressure were measured during Primary Consolidation, which refers to the time-dependent compression process associated with the dissipation of pore pressure. The pore pressure changes were investigated by considering the maximum and the residual values. The development of compression during pore pressure dissipation was analysed to identify the change patterns in volumetric strain–time curves. Three types of change patterns were found during the Primary Consolidation, and the remoulded yield stress was found to be the key factor in classifying the change patterns. The inflexion point is absent for types 1 and 2, indicating that the end of Primary Consolidation cannot be determined by the commonly used Taylor and Casagrande methods. Type 3 shows an inverse ‘S’ shape, suggesting that the end of Primary Consolidation determined ba...
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Experimental study of Primary Consolidation time for structured and destructured clays
Applied Clay Science, 2015Co-Authors: Ling-ling Zeng, Zhen-shun HongAbstract:Abstract Incremental load one-dimensional Consolidation tests were performed on undisturbed and reconstituted specimens of seven natural clays with a predominant clay mineral of illite. Both the settlement and the base pore pressure under step load increments were measured during the dissipation of pore pressure. The change law in the Primary Consolidation time determined by the pore pressure dissipation with increasing stress level is found to be contrary to that determined by the Taylor method and the Casagrande method which are often used in laboratory tests and engineering practice. The Primary Consolidation time determined based on the time-dependent settlement observations is smaller than that determined by the pore pressure dissipation for the natural clays investigated. Pore pressure is generally not completely dissipated at the Primary Consolidation time determined by the Taylor method and the Casagrande method. Such remaining pore pressure may reach a quite high percentage of the step load increment for the investigated specimens. The settlement determined by the Taylor method and the Casagrande method may be significantly underestimated due to the dissipation of remaining pore pressure. Attention should be paid to the possible distortion on Consolidation behavior in laboratory tests and engineering practice due to the remaining pore pressure and the associated settlement.
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On the volumetric strain–time curve patterns of dredged clays during Primary Consolidation
Géotechnique, 2015Co-Authors: Ling-ling Zeng, Zhen-shun Hong, Yu-jun CuiAbstract:International audienceThirteen one-dimensional Consolidation tests with step loading were performed on dredged clays reconstituted at different initial water contents. Both vertical deformation and pore pressure were measured during Primary Consolidation, which refers to the time-dependent compression process associated with the dissipation of pore pressure. The pore pressure changes were investigated by considering the maximum and the residual values. The development of compression during pore pressure dissipation was analysed to identify the change patterns in volumetric strain-time curves. Three types of change patterns were found during the Primary Consolidation, and the remoulded yield stress was found to be the key factor in classifying the change patterns. The inflexion point is absent for types 1 and 2, indicating that the end of Primary Consolidation cannot be determined by the commonly used Taylor and Casagrande methods. Type 3 shows an inverse 'S' shape, suggesting that the end of Primary Consolidation determined based on the compression-time curves occurs before the completion of pore pressure dissipation
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On the volumetric strain–time curve patterns of dredged clays during Primary Consolidation
Géotechnique, 2015Co-Authors: Ling-ling Zeng, Zhen-shun Hong, Yu-jun CuiAbstract:Thirteen one-dimensional Consolidation tests with step loading were performed on dredged clays reconstituted at different initial water contents. Both vertical deformation and pore pressure were measured during Primary Consolidation, which refers to the time-dependent compression process associated with the dissipation of pore pressure. The pore pressure changes were investigated by considering the maximum and the residual values. The development of compression during pore pressure dissipation was analysed to identify the change patterns in volumetric strain–time curves. Three types of change patterns were found during the Primary Consolidation, and the remoulded yield stress was found to be the key factor in classifying the change patterns. The inflexion point is absent for types 1 and 2, indicating that the end of Primary Consolidation cannot be determined by the commonly used Taylor and Casagrande methods. Type 3 shows an inverse ‘S’ shape, suggesting that the end of Primary Consolidation determined ba...
Wenzong Gong - One of the best experts on this subject based on the ideXlab platform.
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Author Correction: Creep in Primary Consolidation with Rate of Loading Approach
Scientific reports, 2020Co-Authors: Dong Wang, Yeqiang Chen, Jianfei Wei, Wenzong GongAbstract:An amendment to this paper has been published and can be accessed via a link at the top of the paper.
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Creep in Primary Consolidation with Rate of Loading Approach.
Scientific Reports, 2019Co-Authors: Gang Bi, Shuna Ni, Yeqiang Chen, Dong Wang, Wenzong GongAbstract:The debate on creep in Primary Consolidation is analysed with a power law model following an approach in which creep is considered as rate of loading. According to this approach, Primary Consolidation is one type of rate of loading. To verify this approach, two types of tests, standard oedometer test and oedometer test with drainage prevented, are conducted on three types of soils (two from NGES and the other from Port of Guangzhou). The result: creep exponents obtained from two kinds of tests agree well with each other. Moreover, the approach is further validated by tracking, for over 80 years, the data from settlement of the case history San Jacinto Monument, which is inconsistent with data calculated from the classical method. In the end, procedure of this approach, with which long term settlement is predicted, is illustrated, and this approach is compared with the classical method.
Ling-ling Zeng - One of the best experts on this subject based on the ideXlab platform.
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On the volumetric strain-time curve patterns of dredged clays during Primary Consolidation
Géotechnique, 2015Co-Authors: Ling-ling Zeng, Zhen-shun Hong, Yu-jun CuiAbstract:Thirteen one-dimensional Consolidation tests with step loading were performed on dredged clays reconstituted at different initial water contents. Both vertical deformation and pore pressure were measured during Primary Consolidation, which refers to the time-dependent compression process associated with the dissipation of pore pressure. The pore pressure changes were investigated by considering the maximum and the residual values. The development of compression during pore pressure dissipation was analysed to identify the change patterns in volumetric strain-time curves. Three types of change patterns were found during the Primary Consolidation, and the remoulded yield stress was found to be the key factor in classifying the change patterns. The inflexion point is absent for types 1 and 2, indicating that the end of Primary Consolidation cannot be determined by the commonly used Taylor and Casagrande methods. Type 3 shows an inverse 'S' shape, suggesting that the end of Primary Consolidation determined based on the compression-time curves occurs before the completion of pore pressure dissipation.
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on the volumetric strain time curve patterns of dredged clays during Primary Consolidation
Geotechnique, 2015Co-Authors: Ling-ling Zeng, Zhen-shun Hong, Yu-jun CuiAbstract:Thirteen one-dimensional Consolidation tests with step loading were performed on dredged clays reconstituted at different initial water contents. Both vertical deformation and pore pressure were measured during Primary Consolidation, which refers to the time-dependent compression process associated with the dissipation of pore pressure. The pore pressure changes were investigated by considering the maximum and the residual values. The development of compression during pore pressure dissipation was analysed to identify the change patterns in volumetric strain–time curves. Three types of change patterns were found during the Primary Consolidation, and the remoulded yield stress was found to be the key factor in classifying the change patterns. The inflexion point is absent for types 1 and 2, indicating that the end of Primary Consolidation cannot be determined by the commonly used Taylor and Casagrande methods. Type 3 shows an inverse ‘S’ shape, suggesting that the end of Primary Consolidation determined ba...
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Experimental study of Primary Consolidation time for structured and destructured clays
Applied Clay Science, 2015Co-Authors: Ling-ling Zeng, Zhen-shun HongAbstract:Abstract Incremental load one-dimensional Consolidation tests were performed on undisturbed and reconstituted specimens of seven natural clays with a predominant clay mineral of illite. Both the settlement and the base pore pressure under step load increments were measured during the dissipation of pore pressure. The change law in the Primary Consolidation time determined by the pore pressure dissipation with increasing stress level is found to be contrary to that determined by the Taylor method and the Casagrande method which are often used in laboratory tests and engineering practice. The Primary Consolidation time determined based on the time-dependent settlement observations is smaller than that determined by the pore pressure dissipation for the natural clays investigated. Pore pressure is generally not completely dissipated at the Primary Consolidation time determined by the Taylor method and the Casagrande method. Such remaining pore pressure may reach a quite high percentage of the step load increment for the investigated specimens. The settlement determined by the Taylor method and the Casagrande method may be significantly underestimated due to the dissipation of remaining pore pressure. Attention should be paid to the possible distortion on Consolidation behavior in laboratory tests and engineering practice due to the remaining pore pressure and the associated settlement.
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On the volumetric strain–time curve patterns of dredged clays during Primary Consolidation
Géotechnique, 2015Co-Authors: Ling-ling Zeng, Zhen-shun Hong, Yu-jun CuiAbstract:International audienceThirteen one-dimensional Consolidation tests with step loading were performed on dredged clays reconstituted at different initial water contents. Both vertical deformation and pore pressure were measured during Primary Consolidation, which refers to the time-dependent compression process associated with the dissipation of pore pressure. The pore pressure changes were investigated by considering the maximum and the residual values. The development of compression during pore pressure dissipation was analysed to identify the change patterns in volumetric strain-time curves. Three types of change patterns were found during the Primary Consolidation, and the remoulded yield stress was found to be the key factor in classifying the change patterns. The inflexion point is absent for types 1 and 2, indicating that the end of Primary Consolidation cannot be determined by the commonly used Taylor and Casagrande methods. Type 3 shows an inverse 'S' shape, suggesting that the end of Primary Consolidation determined based on the compression-time curves occurs before the completion of pore pressure dissipation
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On the volumetric strain–time curve patterns of dredged clays during Primary Consolidation
Géotechnique, 2015Co-Authors: Ling-ling Zeng, Zhen-shun Hong, Yu-jun CuiAbstract:Thirteen one-dimensional Consolidation tests with step loading were performed on dredged clays reconstituted at different initial water contents. Both vertical deformation and pore pressure were measured during Primary Consolidation, which refers to the time-dependent compression process associated with the dissipation of pore pressure. The pore pressure changes were investigated by considering the maximum and the residual values. The development of compression during pore pressure dissipation was analysed to identify the change patterns in volumetric strain–time curves. Three types of change patterns were found during the Primary Consolidation, and the remoulded yield stress was found to be the key factor in classifying the change patterns. The inflexion point is absent for types 1 and 2, indicating that the end of Primary Consolidation cannot be determined by the commonly used Taylor and Casagrande methods. Type 3 shows an inverse ‘S’ shape, suggesting that the end of Primary Consolidation determined ba...
