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Y. J. Du
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 1 
FIELD PROPERTIES AND SETTLEMENT CALCULATION OF SOIL-CEMENT COLUMN IMPROVED SOFT SUBSOIL - A CASE STUDY J. C. Chai; S. Y. Liu; Y. J. Du
Lowland Technology International Vol 4 No 2, Dec (2002)
Publisher : International Association of Lowland Technology

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Abstract

The unconfined compression strength, standard penetration test (SPT) results for soil-cement columns and the field loading tests results of the composite subsoil at Lian-Yun-Gang section, Xu - Lian expressway, China, were presented. The Methods for calculating the settlement of the soil-cement column improved soft subsoil were discussed. It is recommended that the stiffness of the "slab" on the top of the improved subsoil should be flexible "slab". the equilibrium method for the improved layer and the average stress method for the underlying unimproved soft layer are prefered, while in the case of a stiff "slab", the average modulus method for the improved layer and the combined method for the underlying unimproved layer are prefered. Finally, the settlements of the soil-cement column improved subsoil at Lian-Yun-Gang section were evaluated by the suggested methods and compared with the field data. The stress concentration ratio (n) is back-calculated, and it showed that n value increased with the increased of the area replacement ratio.
EARTH SEWING TECHNIQUE FOR THE PRESERVATION OF FANASAKO HISTORICAL KILN SITES X. J. Chai; S. Hayashi; Y. J. Du
Lowland Technology International Vol 6 No 1, June (2004)
Publisher : International Association of Lowland Technology

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The Funasako historical klin sites, which are located in the northern part Kyushu Island in Japan, have been considered as public exhibition areas. This requires preservation of the kiln remains by reinforcement of the soil. Considering the complicated local topography, the reinforcement method that was proposed is a combination of chemical grouting and soil nailing, and is termed the Earth Sewing Technique (EST) in this paper. In order to prevent disturbance of the soil in the kiln remains, a drilling hole diameter for soil nailing of 7 mm with a tendon (bolt) that has a diameter of 3 mm was selected. Field full-scale pullout test at a model kiln site were carried out before applying the reinforcement technique to the real historical kiln sites. This paper presents the field pullout results and the results of a series of laboratory pullout test that were conducted to investigate the critical factors affecting the perfomance of the EST. Design parameters have been recommended based on rational interpretation of the field and laboratory pullout test results. The pullout strength-water content relationships were found to be very useful for understanding and evaluating the shear strength capacity of soil nailing in partially saturated cohesive soils.
INVESTIGATION ON SOME FACTORS CONTROLLING THE SORPTION OF HEAVY METALS ON ARIAKE CLAY Y. J. Du; S. Hayashi
Lowland Technology International Vol 7 No 1, June (2005)
Publisher : International Association of Lowland Technology

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Sorption of contaminant is one of the key mechanisms in controlling transport of contaminant in clay barrier. In this study, the potential sorption of heavy metals on Ariake clay, which is a typical Japanese marine clay, is examined. Two types of heavy metals, Cd2+ and Pb2+, were selected as key contaminants and series of batch tests were performed for investigating factors controlling the sorption of Cd2+ and Pb2+ on Ariake clay. The batch test results show that the sorption of Cd2+ and Pb2+ on the Ariake clay arrived at an equilibrium condition less than the contact time prescribed by the ASTM and US EPA standards. It is found that the sorption was significantly controlled by the solid: solution ratio. With the increase in the solid: solution ratio, the sorption of Cd2+ decreased. The batch test results show that the sorption of Cd2+ increased with the increase in the pH of solution. The influence of pH on the sorption was found to be solid: solution-dependent. At relatively lower solid: solution ratio, the sorption of Cd2+ increased with increasing pH, whereas it marginally increased at relatively higher solid: solution ratio. It is concluded that the solid: solution ratio could be the crucial factor for controlling the sorption of heavy metals on the Ariake clay.
NOVEL THERMO-PVD CONSOLIDATION TECHNIQUE FOR SOFT SOILS C. Pothiraksanon; D. T. Bergado; H. M. Abuel-Naga; S. Hayashi; Y. J. Du
Lowland Technology International Vol 9 No 2, Dec (2007)
Publisher : International Association of Lowland Technology

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Previous research efforts on investigating the thermo-hydro-mechanical behaviour of fine grained soils as well as recent extensive experiments conducted on soft Bangkok clay have demonstrated that saturated fine-grained soils subjected to temperature less than boiling point of water (100OC) undergo volumetric and shear strength changes depending on the stress history. These features encouraged employing the thermal load only, up to 90OC, or in combination with mechanical loading as ground improvement technique. This paper addressed the applicability of this technique through a series of large oedometer tests conducted on soft Bangkok clay. Heating was achieved using flexible wire heater attached to the PVD point or using separate line heat source. The clay has been subjected to either thermal load or thermo-mechanical load. The test results show that a combination of the thermal and mechanical load gives promising results and is a viable technique since it accelerates the rate of consolidation and increases the amount of total settlement. This behavior can be attributed to the increase in the soil hydraulic conductivity as the soil temperature increases. Therefore, raising the soil temperature during the preloading period can enhance the performance of the PVD, particularly, by reducing the drainage retardation effects due to the smear zone around PVD.
EVALUATION OF PERFORMANCE OF CHINESE STANDARD MUNICIPAL SOLID WASTE LANDFILL BOTTOM LINER SYSTEMS Y. J. Du; S. Y. Liu; S. Hayashi
Lowland Technology International Vol 10 No 1, June (2008)
Publisher : International Association of Lowland Technology

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Abstract

It is reported that nearly 80 % of the Chinese municipal solid waste (MSW) landfills were open-dump without strict landfill bottom liners. A serious environmental pollution has been exposed to landfill impacts. To solve this problem, Chinese Government prescribed standard MSW landfill bottom liners. However, very limited research has been conducted to evaluate the performance of the standard MSW landfill bottom liners prescribed Chinese Government. In this paper, it was assumed that the two standard Chinese landfill liners were applied in assumed field scenario, in which an aquifer was below the landfill. With the one-dimensional advection-diffusion-dispersion theory of contaminant transport, the impacts of the landfills on the aquifer were assessed. The performance of the two types of Chinese MSW landfill bottom liner systems was evaluated based on: 1) the leakage rate through the liners which were applied in assumed landfills; 2) the peak concentration of the target contaminant in an aquifer overlain by the assumed landfills, and 3) the maximum total mass per unit area of the target contaminant discharged into the aquifer. The performance of the German standard MSW landfill bottom liner system was evaluated and compared with that of Chinese ones. The calculated leakage rate, peak concentration and the maximum total mass per unit area in the aquifer of the target contaminant show that the performance of the Chinese standard landfill liner Type 2 is practically the same as that of the German standard landfill liner, while the Chinese standard liner Type 1 is less effective, with regarding the mitigation of the impact of landfills.
CONSOLIDATION MECHANISM OF GROUND IMPROVED BY A COMBINED DJMPVD METHOD D. W. Zhang; S. Y. Liu; Y. J. Du; G. Y. Du
Lowland Technology International Vol 11 No 2, Dec (2009)
Publisher : International Association of Lowland Technology

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Dry Jet Mixed (DJM) and Prefabricated Vertical Drains (PVDs) were used in combination to enhance the performance of soft ground improvement in Huai-yan highway in China. To investigate the consolidation mechanism of ground improved by a combined DJM-PVD method, coupled two-dimensional mechanical and hydraulic numerical modeling was conducted in this study to analyze the well-instrumented ground improved by a combined DJM-PVD method in Huai-yan highway in China. The results indicate that the consolidation of the ground improved by a combined DJM-PVD method is accelerated by the drainage of PVDs, the stress concentration on DJM columns and the excess pore water pressure gradient resulting from the stress transfer between the surrounding soil and columns. It is observed that the high drainage capacity of PVDs accelerates the dissipation of the excess pore water pressure. The accelerated dissipation is explained as that upon the embankment loading, the stress concentration on the column occurs due to its higher stiffness than that of the surrounding soil, and thereby results in the reduction of the excess pore water pressure in the soil. The differential settlement develops between the soil and the column induces the transfer of stress between surrounding soil and column, which results in pore water pressure gradient in the surrounding soil and accelerates the consolidation.
A CASE STUDY OF THE BEHAVIOR OF SOIL-NAIL SUPPORTED DEEP MIXED WALL IN THE SOFT DEPOSIT OF SHANGHAI L. Ma; S. L. Shen; Y. J. Du; W. J. Sun
Lowland Technology International Vol 13 No 2, Dec (2011)
Publisher : International Association of Lowland Technology

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This paper presents a case study of an excavation retained by soil-nail supported deep mixed (DM) wall (DMSNW) in soft deposit of Shanghai, China. The soft deposit in Shanghai is Quaternary sediment with silt content over 50% and clay content of about 40%. The strength of this deposit is very low and the sensitivity is very high. In order to retain the excavation in the soft deposit, soil-nail supported DM wall is generally adopted when the excavation depth is less than 6 m. This paper presents an investigation on the interaction mechanism between nail and surrounding soil through a field case. A two-dimension finite element method (2D-FEM) was conducted. The effectiveness of 2DFEM is verified via comparing calculated DM wall displacement with the field measured value. Based on the FEM result, the importance of four key design factors, e.g. nail length, nail spacing, thickness of DM wall, and stiffness of DM wall, are discussed. The results indicate that FEM analysis is an efficient way to predict the displacement and internal force of nails. Finally, a design chart is proposed for the soil-nail supported DM wall used in excavation practice.
Co-Authors C. Pothiraksanon D. T. Bergado D. W. Zhang G. Y. Du H. M. Abuel-Naga J. C. Chai L. Ma S. Hayashi S. L. Shen S. Y. Liu W. J. Sun X. J. Chai