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Laboratory model study of newly deposited dredger fills using improved multiple-vacuum preloading technique

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Journal of Rock Mechanics and Geotechnical Engineering 2017年第5期9卷 924-935页

作者： Jingjin Liu Huayang Lei Gang Zheng Haizuo Zhou Xuelian Zhang School of Civil Engineering Tianjin University Tianjin 300072 China Key Laboratory of Coast Civil Structure Safety of Ministry of Education Tianjin University Tianjin 300072 China State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin University Tianjin 300072 China

Problems continue to be encountered concerning the traditional vacuum preloading method in field during the treatment of newly deposited dredger *** this paper,an improved multiple-vacuum preloading method was developed to consolidate newly dredger fills that are hydraulically placed in seawater for land reclamation in Lingang Industrial Zone of Tianjin City,*** this multiplevacuum preloading method,the newly deposited dredger fills could be treated effectively by adopting a novel moisture separator and a rapid improvement technique without sand cushion.A series of model tests was conducted in the laboratory for comparing the results from the multiple-vacuum preloading method and the traditional *** piezometers and settlement plates were installed to measure the variations in excess pore water pressures and moisture content,and vane shear strength was measured at different *** testing results indicate that water dischargeetime curves obtained by the traditional vacuum preloading method can be divided into three phases:rapid growth phase,slow growth phase,and steady *** to the process of fluid flow concentrated along tiny ripples and building of larger channels inside soils during the whole vacuum loading process,the fluctuations of pore water pressure during each loading step are divided into three phases:steady phase,rapid dissipation phase,and slow dissipation *** optimal loading pattern which could have a best treatment effect was proposed for calculating the water discharge and pore water pressure of soil using the improved multiple-vacuum preloading *** the newly deposited dredger fills at Lingang Industrial Zone of Tianjin City,the best loading step was 20 kPa and the loading of 40-50 k Pa produced the highest drainage *** measured moisture content and vane shear strength were discussed in terms of the effect of reinforcement,both of which indicate that the multiple-vacuum preloading method has a

关键词： Model tests vacuum preloading Ultra-soft soil Dredger fills Cost effectiveness

Laboratory study for effects of vacuum preloading on physical and mechanical properties of soft clayey soils

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Journal of Southeast University(English Edition) 2005年第1期21卷 82-87页

作者： Ali H.Mahfouz 刘汉龙赵仲辉高玉峰张秀勇河海大学岩土工程研究所

A new triaxial apparatus was designed and manufactured. It is able to applysurcharge and combined vacuum-surcharge pressures on soil samples, and allows for monitoring ofexcess pore-water pressure, axial strain or settlement, and volumetric strain during the process ofconsolidation. Tests were performed using the apparatus on undisturbed soft clayey soil samples,which were collected from Wenzhou, Zhejiang Province, China, at average natural water content 72. 5%. The consolidation behavior of theclay has no rigorous difference, whether it is consolidatedunder the vacuum, surcharge, or combined vacuum-surcharge preloading. The study shows that somephysical properties of the soft clayey soils are changed and mechanical properties are improved tosupport excessive loads transferred to the soil foundation due to construction.

关键词： soft soil vacuum preloading consolidation permeability strength

Improvement of silty clay by vacuum preloading incorporated with electroosmotic method

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Journal of Rock Mechanics and Geotechnical Engineering 2010年第4期2卷 365-372页

作者： M. Q. Vu Department of Soil Mechanics and Foundation Engineering National University of Civil Engineering

A laboratory test was performed to assess the effectiveness of vacuum preloading incorporated with electroosmotic (EOM) treatment on silty clay (combined method) for reclamation projects like new disposal ponds, where the horizontal electrode configurations beneath the soil layer were possible and the drainage pipes and the prefabricated vertical drains (PVDs) system could be easily installed in advance before the sludge dragged from sea bed or river bed was filled into the site. Three groups of tests were conducted on the silty clay from Qinhuai River in Nanjing, China. The model is able to apply vacuum pressure at the bottom of the soil layer and a direct current electric field simultaneously. It is also possible to measure the pore pressures at different depths of soil column, and the changes in settlement and volume with the elapsed time. In this study, the vacuum preloading method, vacuum preloading applied at the bottom (VAB method), was applied and the cathodes were installed beneath the soil layer. The results obtained indicate substantial reduction in water content, and increases in dry density and undrained shear strength in comparison with those obtained by the vacuum preloading only, particularly at the positions close to the anode. The combined method utilizes the vertical drainage flow created by the electroosmosis integrating the horizontal drainage flow created mostly by the vacuum pressure. The total drainage flow can be calculated as a result of the vertical drainage flow by electroosmosis only and the horizontal drainage flow by the vacuum preloading only. The way of placement of the cathode and the anode in the combined method also overcomes the disadvantage of EOM method itself, i.e. the appearance of cracks between the anode and the surrounding soil. Moreover, it is observed that the vacuum preloading plays a primary role in earlier stage in deduction of free pore water; meanwhile, the electroosmotic method is more efficient in later stage for

关键词： vacuum preloading VAB method soil improvement consolidation pore pressure undrained shear strength dry density electroosmotic method

CREEP ANALYSIS OF SOFT CLAYEY SOILS UNDER CONSOLIDATION BY vacuum preloading METHOD

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CREEP ANALYSIS OF SOFT CLAYEY SOILS UNDER CONSOLIDATION BY V...

An integrated method for the rapid dewatering and solidification/stabilization of dredged contaminated sediment with a high water content

中日岩土工程学术会议

作者： ALI H.MAHFOUZ Doctor Department of Water Conservancy and Hydropower EngineeringHohai UniversityNanjing 210098China Department of Geological ＆ Geophysical EngineeringSuez Canal UniversitySuezEgypt

＜正＞ Compressibility of clay depends on the duration of loading and the rate of loading, as well as loading magnitude. This paper describes the mechanism of time-dependent compressibility of clay under vacuum preloading method that can be modeled for creep in a single consistent analysis. The theory provides a consistent method for using all of the information obtained from laboratory consolidation tests to estimate the rate and magnitude of field settlements. Hence to predict, the long term consolidation of soft clayey soils.

关键词： vacuum preloading Soft Clay Creep Time-Dependent Consolidation

来源： cnki会议评论

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Frontiers of Environmental Science & Engineering 2021年第4期15卷 229-240页

作者： Hefu Pu Aamir Khan Mastoi Xunlong Chen Dingbao Song Jinwei Qiu Peng Yang Institute of Geotechnical and Underground Engineering Huazhong University of Science and TechnologyWuhan430074China Department of Civil Engineering Quaid-e-Awam University of EngineeringSciences and TechnologySindh67450Pakistan

To more efficiently treat the dredged contaminated sediment(DCS)with a high water content,this study proposes an integrated method(called PHDVPSS)that uses the solidifying/stabilizing(S/S)agents and prefabricated horizontal drain(PHD)assisted by vacuum pressure(VP).Using this method,dewatering and solidification/stabilization can be carried out simultaneously such that the treatment time can be significantly shortened and the treatment efficacy can be significantly improved.A series of model tests was conducted to investigate the effectiveness of the proposed *** results indicated that the proposed PHDVPSS method showed superior performance compared to the conventional S/S method that uses Portland cement(PC)directly without prior *** 56-day unconfined compressive strength of DCS treated by the proposed method with GGBS-MgO as the binder is 12–17 times higher than that by the conventional S/S *** treated by the PHDVPSS method exhibited continuous decrease in leaching concentration of Zn with increasing curing *** reduction of Zn leachability is more obvious when using GGBS-MgO as the binder than when using PC,because GGBS-MgO increased the residual fraction and decreased the acid soluble fraction of *** microstructure analysis reveals the formation of hydrotalcite in GGBS-MgO binder,which resulted in higher mechanical strength and higher Zn stabilization efficiency.

关键词： Dredged contaminated sediment Dewatering Solidification/stabilization vacuum preloading Prefabricated horizontal drain Heavy metal