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S. Y. Liu
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Civil Engineering, Building, Construction & Architecture Engineering Transportation

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PREDICTION OF SOIL WATER CHARACTERISTIC CURVE USING PHYSICALLY BASED SCALING TECHNIQUE S. Y. Liu; N. Yasufuku; Q. Liu; J. Yu
Lowland Technology International Vol 15 No 1, June (2013)
Publisher : International Association of Lowland Technology

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Abstract

The soil water characteristic curve (SWCC) is an important hydraulic parameter for modeling water flow and contaminant transport in the vadose zone. However, direct measurement of the SWCC is still difficult. The Arya and Paris (AP) model estimates the SWCC from particle-size distribution curve (PSD) based on the shape similarity of the two curves. They introduced an empirical parameter, a, used to scale pore attributes from hypothetical formations to natural structure. Several approaches have been used to derive a. However, the calculation precedures of these approaches are either quite complicated or are developed without paying much attention to the physical significance of the soil properties. In the present paper the physically based scaling technique (PBS) was applied to derive a for the AP model. Fifty soil samples, representing a range of textures that include sand, sandy loam, loam, sit loam, and clay, were selected from UNSODA hydraulic property database for calculating a using PBS approach. In addition, nineteen soil samples with different textures were used to verify effectiveness of proposed a values. The result compared with other approaches show that the PBS technique combine with the AP model is a more useful and easier approach to predict SWCC from PSD.
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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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.
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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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.
Co-Authors D. W. Zhang G. Y. Du J. C. Chai J. Yu N. Yasufuku Q. Liu S. Hayashi Y. J. Du