Stress ratio–fabric relationships of granular soils under axi-symmetric stress and plane-strain loading     

Eui-Ryong Jang  Young-Hoon Jung  Choong-Ki Chung 《Computers and Geotechnics》2010,37(7-8):913-929

This paper investigates the relationship between the stress ratio and the fabric of frictional material under three-dimensional stress. The spatial distribution function of the contact normal was derived to describe the heterogeneous distribution of the micro-structural architecture. Discrete element simulations were conducted using an assembly consisting of 10,000 spherical particles. Sixteen stress probe experiments were simulated under both axi-symmetric stress and plane-strain conditions. The numerical results show that a change in the direction of the stress probe does not significantly affect the evolution of the fabric structure in the vertical plane. Regardless of whether the material is subjected to axi-symmetric stress or plane strain, the degree of fabric anisotropy shows a unique relationship with the stress ratio. The modified stress ratio, as theoretically derived from a micromechanics formulation, is able to separately measure micro-structures in the vertical and horizontal planes. The distribution function proposed in this study generally performs well in estimating the heterogeneous distribution of the contact normal. A higher-order distribution function is required to improve the predictability of the contact normal distribution for increasing stress-ratio paths.  相似文献   

Using multiple‐variable indicator kriging to assess groundwater quality for irrigation in the aquifers of the Choushui River alluvial fan     

Cheng‐Shin Jang  Shih‐Kai Chen  Lin Ching‐Chieh 《水文研究》2008,22(22):4477-4489

This work attempted to locate clean and safe groundwater for irrigation use in the Choushui River alluvial fan. Multiple‐variable indicator kriging (MVIK) was adopted to evaluate numerous hydrochemical parameters for a standard of water quality for irrigation in Taiwan. Many hydrochemical parameters in groundwater were distinguished into three main categories—salinity/sodium hazard, nitrogen hazard and heavy metal hazard. Safe and potential hazardous regions of groundwater for irrigation were delineated according to different probabilities estimated by MVIK. The probabilistic results of the classifications gave an opportunity to explore the spatial uncertainty of the hazards and helped government administrators establish a sound policy associated with the development and management of groundwater resources. Analysis of the results indicate that the central distal‐fan and mid‐fan aquifers are the best places to extract clean and safe groundwater for irrigation, and the deep aquifer (exceeding 200 m depth) has wider regions with clean and safe groundwater for irrigation than shallow aquifers. The northern and southern aquifers, with multiple hazards, limit groundwater use for irrigation. Although the proximal‐fan aquifer is a zone of groundwater recharge, the high nitrogen content seriously affects the environment and is not suitable for irrigation use. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Risk-based assessment of arsenic-affected aquacultural water in blackfoot disease hyperendemic areas     

Cheng-Shin Jang  Kao-Hung Lin  Chen-Wuing Liu  Ming-Chao Lin 《Stochastic Environmental Research and Risk Assessment (SERRA)》2009,23(5):603-612

This work explored a risk-based arsenic (As) regulation in farmed pond water by ingesting tilapia (Oreochromis mossambicus) in blackfoot disease hyperendemic areas and discussed a rational As regulation in pond water. Monte Carlo analysis was used to propagate the parameter uncertainty and to assess probabilistically regulation risks. A dynamic scheme of groundwater management was proposed that curves of utilization ratios against As concentrations in groundwater were established based on the risk-based regulation. The 5th to 95th percentiles of risks range from 3.5 × 10⁻⁷ to 6.0 × 10⁻⁵ via ingesting the farmed tilapia under the current As regulation in farmed pond water in Taiwan, 50 μg/L. To compare to inorganic As regulation in drinking water, the current As regulation in farmed pond water does not pose a great threat to human health, but it is unsafe. Therefore, this study suggests that the regulation of As in farmed pond water is revised to be 25 μg/L.  相似文献   

Groutability of cement‐based grout with consideration of viscosity and filtration phenomenon     

Jong‐Sun Kim  In‐Mo Lee  Jae‐Hyuk Jang  Hangseok Choi 《国际地质力学数值与分析法杂志》2009,33(16):1771-1797

The groutability depends on the properties of the grout, its injection processes, and on the mechanical properties of the soil formation. During the process of pouring cement‐based grouting into a porous medium, a variation with time occurs in the viscosity of grout suspension. In addition, the particle filtration phenomenon will limit the expansion of the grouted zone because cement particles are progressively stagnant within the soil matrix. In this paper, a closed‐form solution was derived by implementing the mass balance equations and the generalized phenomenological filtration law, which can be used to evaluate the deposition of cement‐based grout in the soil matrix. The closed‐form solution relevant to a particular spherical flow was modified by a step‐wise numerical calculation, considering the variable viscosity caused by a chemical reaction, and the decrease in porosity resulting from grout particle deposition in the soil pores. A series of pilot‐scale chamber injection tests was performed to verify that the developed step‐wise numerical calculation is able to evaluate the injectable volume of grout and the deposition of grout particles. The results of the chamber injection tests concurred well with that of the step‐wise numerical calculation. Based on the filtration phenomenon, a viable approach for estimating the groutability of cement‐based grout in a porous medium was also suggested, which might facilitate a new insight in the design of the grouting process. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Assessing the impacts of land use changes on watershed hydrology using MIKE SHE   总被引：2，自引：0，他引：2  

Sangjun Im  Hyeonjun Kim  Chulgyum Kim  Cheolhee Jang 《Environmental Geology》2009,57(1):231-239

A fully distributed, physically-based hydrologic modeling system, MIKE SHE, was used in this study to investigate whole-watershed hydrologic response to land use changes within the Gyeongancheon watershed in Korea. A grid of 200 × 200 m was established to represent spatial variations in geology, soil, and land use. Initial model performance was evaluated by comparing observed and simulated streamflow from 1988 to 1991. Results indicated that the calibrated MIKE SHE model was able to predict streamflow well during the calibration and validation periods. Proportional changes in five classes of land use within the watershed were derived from multi-temporal Landsat TM imageries taken in 1980, 1990 and 2000. These imageries revealed that the watershed experienced conversion of approximately 10% non-urban area to urban area between 1980 and 2000. The calibrated MIKE SHE model was then programmed to repeatedly analyze an artificial dataset under the various land use proportions identified in the Landsat TM imageries. The analysis was made to quantitatively assess the impact of land use changes (predominantly urbanization) on watershed hydrology. There were increases in total runoff (5.5%) and overland flow (24.8%) as a response to the land use change.  相似文献   

Evaluation of seismic displacements of quay walls   总被引：2，自引：0，他引：2  

Sung-Ryul Kim  In-Sung Jang  Choong-Ki Chung  Myoung-Mo Kim   《Soil Dynamics and Earthquake Engineering》2005,25(6):451-459

A new simplified dynamic analysis method is proposed to predict the seismic sliding displacement of quay walls by considering the variation of wall thrust, which is influenced by the excess pore pressure developed in backfill during earthquakes. The method uses the Newmark sliding block concept and the variable yield acceleration, which varies according to the wall thrust, to calculate the quay wall displacement.A series of 1 g shaking table tests were executed to verify the applicability of the proposed method, and a parametric study was performed. The shaking table tests verified that the proposed method properly predicts the wall displacement, and the parametric study showed that the evaluation of a realistic wall displacement is as important as the analysis of liquefaction potential for judging the stability of quay walls.  相似文献   

Photometric behaviour of the Be star EW Lacertae     

Jang Hae Jeong  Chang Won Suh  Il-Seong Nha 《Astrophysics and Space Science》1986,119(1):73-76

The night-to-night and short-term variations inUBV light curves of EW Lac which were made during 1982–1984 at Yonsei University Observatory are discussed. The long-term variability in the photometric behaviour of the star is examined with our own data as well as those of Harmanecet al. (1980).Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.Yonsei University Observatory Contribution No. 23.  相似文献   

新疆黑孜断层现今活动特征研究及有关问题的讨论   总被引：3，自引：0，他引：3  

蒋靖祥  温和平  尹光华  刘辉 《中国地震》2001,17(3):246-252

在前人研究的基础上，用近年黑孜水库的形变测量资料重新计算了黑孜断层的微量位移，表明自1973年以来黑孜断层活动特征发生了变化，大致经历了4个阶段；其中第3个阶段有正断层特征，其余3个阶段属逆断层特征。水库大坝的修建及水库的蓄水对断层的现今活动具有重要影响，甚至改变了某个阶段断层活动的性状。地震活动对形变测量资料、断层活动也有一定程度的影响。  相似文献   

Internal soil moisture response to rainfall-induced slope failures and debris discharge   总被引：2，自引：0，他引：2  

Ching-Chuan Huang  Chien-Li Lo  Jia-Shiun Jang  Lih-Kang Hwu   《Engineering Geology》2008,101(3-4):134-145

Predictions of rainfall-induced fast-moving mass flow and/or debris flows require better knowledge of the mechanism controlling the debris discharge of slopes in debris source areas. A series of rainfall tests on 0.32 m-deep, 0.7 m-high, 1.35 m-wide sandy slopes resting on a bi-linear impermeable rigid base was performed. Soil moisture content and solid discharge measurements were performed to gain insights into the rainfall-induced retrogressive slope failure. The solid (or debris) discharge is a result of the wash-out of the fluidized slope toe by the interflow along the soil–bedrock interface. Characteristics of the failure process for the slopes are represented by mass wasting curves or ‘solid discharge (Q_s) vs. time (t)’ curves which are functions of the rainfall intensity and/or the cumulative rainfall. The mass wasting curves have inflection points representing transitions from minor toe failures into remarkable retrogressive failures. The first inflection point of the soil moisture (ω) vs. t curve measured at the soil–bedrock interface signaling the arrival of the descending ‘wet front’, may serve as a precursor for predicting the onset of an abrupt solid discharge induced by shallow slope failures. The time of peak water content measured at the soil–bedrock interface may approximate the time of 5% total solid volume discharge. Up to the time of 5% of total slope volume discharge, a fully saturated state (S_r  100%) was never observed at the 0.2 m-below-surface zone; however, it was observed along the soil–bedrock interface at near-toe zone of the slope, regardless of the intensity of rainfall investigated. Retrogressive failures were essentially associated with nonuniformly distributed water content in the slope. For both the 0.2 m-below-surface zone and the soil–bedrock interface, a more uniform distribution of S_r along the full height of the slope was found for slopes subjected to high rainfall intensities of 47 and 65 mm/h than that for the slope subjected to a low rainfall intensity of 23 mm/h. At the inflection point of the Q_s vs. t curve and 5% of total solid volume discharge, values of S_r at a certain distance from the toe for the soil–bedrock interface were higher than those measured at the same distance from the toe for the 0.2 m-below-surface zone, indicating the effect of infiltration-induced interflow along the soil–bedrock interface and its effects on the fluidization of the slope toe and the retrogressive failure of the slope.  相似文献   

Evidence of the observed change in the atmosphere–ocean interactions over the South China Sea during summer in a regional climate model     

Hye-Yeong Jang  Sang-Wook Yeh  Eun-Chul Chang  Baek-Min Kim 《Meteorology and Atmospheric Physics》2016,128(5):639-648

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