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It is critical to understand and quantify the temporal and spatial variability in hillslope hydrological data in order to advance hillslope hydrological studies, evaluate distributed parameter hydrological models, analyse variability in hydrological response of slopes and design efficient field data sampling networks. The spatial and temporal variability of field‐measured pore‐water pressures in three residual soil slopes in Singapore was investigated using geostatistical methods. Parameters of the semivariograms, namely the range, sill and nugget effect, revealed interesting insights into the spatial structure of the temporal situation of pore‐water pressures in the slopes. While informative, mean estimates have been shown to be inadequate for modelling purposes, indicator semivariograms together with mean prediction by kriging provide a better form of model input. Results also indicate that significant temporal and spatial variability in pore‐water pressures exists in the slope profile and thereby induces variability in hydrological response of the slope. Spatial and temporal variability in pore‐water pressure decreases with increasing soil depth. The variability decreases during wet conditions as the slope approaches near saturation and the variability increases with high matric suction development following rainfall periods. Variability in pore‐water pressures is greatest at shallow depths and near the slope crest and is strongly influenced by the combined action of microclimate, vegetation and soil properties. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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Response parameters for characterization of infiltration 总被引：2，自引：2，他引：0
H. Rahardjo T. H. Ong R. B. Rezaur E. C. Leong D. G. Fredlund 《Environmental Earth Sciences》2010,60(7):1369-1380
Rainwater infiltration is of particular interest with respect to slope stability hazard management. The process of rainfall infiltration into unsaturated soil is complex due to the number of soil parameters involved and the random nature of moisture flux boundary conditions. In this paper, the effect of rainfall intensity on infiltration is investigated through the use of finite element seepage modeling for a 5 m high soil column subjected to various rainfall intensities. The numerical modeling study identified three response parameters that can be used to describe one-dimensional infiltration into an unsaturated soil. The response parameters are the depth of wetting front, the matric suction reduction depth, and the sectional infiltration rate. The practical application of the rainfall response parameters in slope stability analysis is illustrated. 相似文献
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K. K. Aung H. Rahardjo E. C. Leong D. G. Toll 《Geotechnical and Geological Engineering》2001,19(3-4):401-416
Soil–water characteristic curve (SWCC) is an important tool for determining the engineering properties of unsaturated soil. This depends on the size and distribution of pore structures which control the permeability and amount of volume change. Mercury Intrusion Porosimetry tests can be used to determine the size, amount and distribution of pore spaces of the soil in a shorter time period compared to the pressure plate test. A soil-air characteristic curve (SACC) can be determined using the volumetric air content as measured in the Mercury Intrusion Porosimetry test. In this paper, SACC parameters are introduced. There appears to be a relationship between the soil-air characteristic curve and the soil-water characteristic curve of a soil. Relations between the SACC and the SWCC parameters are analysed in the light of unsaturated soil mechanics. The results indicate that the pore size distribution of a residual soil varies with depth due to differing degrees of weathering. 相似文献
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Horizontal drains have been commonly used in stabilising unsaturated residual soil slopes. This study examines the effectiveness of horizontal drains in stabilising residual soil slopes against rainfall-induced slope failures under a tropical climate. The study includes field instrumentation at two residual soil slopes complemented with a parametric study relating to drain position. Field monitoring results indicate that rainfall infiltration is limited to a certain depth below which infiltration becomes insignificant. This zone tends to be unsuitable for horizontal drains. Horizontal drains were found to be most effective when located at the base of a slope. The parametric study indicated conditions under which horizontal drains are effective or ineffective in improving the stability of a slope. It was also found that horizontal drains have little role in minimising infiltration in an unsaturated residual soil slope. Benefits of using horizontal drains can be obtained through the lowering of the water table. 相似文献
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Acta Geotechnica - Many shallow foundations are constructed within the soil layer above the groundwater table, where the soil remains unsaturated, and the failure of shallow foundation is mostly... 相似文献
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Acta Geotechnica - During heavy rainfalls, the surface soil on a slope may be eroded and the erosion is much dependent on the tensile strength of soil. In addition, the tensile strength of soil is... 相似文献
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Harianto Rahardjo Mărgărit-Mircea Nistor Nurly Gofar Alfrendo Satyanaga Qin Xiaosheng Sabrina Ip Chui Yee 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2020,14(3):177-191
ABSTRACT This paper presents the spatial distribution, variation and trend of 5-day antecedent rainfall in Singapore based on rainfall data from 22 meteorological stations. The effect of climate was analyzed by dividing the study period into three decades i.e. Decade 1: 1982–1991, Decade 2: 1992–2001 and Decade 3: 2002–2011. Kriging interpolation was used for rainfall mapping. The results show that spatial distribution of 5-day antecedent rainfall does not coincide with that of the annual rainfall. The maximum annual rainfall occurred in the northwestern side of Singapore. On the other hand, the maximum 5-day antecedent rainfall occurred in the north and northeastern sides. The results of this study suggest that the climate change has increased the amount of 5-day antecedent rainfall quite significantly, i.e. from 420.5 (1987) to 592.9 mm (2006), thus affecting the vulnerability of the area with respect to rainfall-induced slope failure. The analyses also showed that most of slope failures were located in the north and northeast of Singapore between December and earlier March. More slope failures were observed in Decade 3 as compared to Decades 1 and 2. In other words, the analysis confirmed that 5-day antecedent rainfall had affected the slope stability in Singapore. 相似文献
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Residual soils are generally characterised by a low coefficient of permeability and high shrinkage potential. Several soil improvement methods can be applied to overcome these problems, including mixing the residual soil with coarse-grained soils. In order to study the effects of varying coarse-grained materials on the hydraulic properties and shrinkage characteristics of residual soils, a local residual soil was mixed with different percentages of a gravelly sand and a medium sand. The hydraulic properties and shrinkage potential of the residual soil and the soil mixtures were investigated. The measurements showed that increasing the amount of coarse-grained materials increased the saturated permeability and reduced the shrinkage potential of the residual soil mixture. Increasing the amount of coarse-grained materials in the residual soil produced changes in several key parameters of soil-water characteristic curve (e.g., the slope, the air-entry value, the residual matric suction, and the residual volumetric water content), as well as the unsaturated permeabilities of the soil mixtures. 相似文献
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Effects of coarse-grained material on hydraulic properties and shear strength of top soil 总被引：2，自引：0，他引：2
Sidewalk failures associated with top soil of low shear strength are a common problem in urban areas. Mixing top soil with granite chips can be used to increase its permeability and shear strength. The effects of mixing granite chips with top soils on the hydraulic properties and shear strength under saturated and unsaturated conditions were investigated in this study. The results showed that the mixing top soils with granite chips caused changes in several key parameters of the soil–water characteristic curve (e.g., the air-entry value, the residual matric suction, and the residual volumetric water content) and the unsaturated permeability of the top soils. The saturated permeability and shear strength of the soil mixture increased with increasing content of granite chips. 相似文献