Values Of Soil Parameters Research Articles

Gravity changes associated with variations in local land-water distributions: Observations and hydrological modeling at Isawa Fan, northern Japan

Gravity changes associated with variations in local land-water distributions have been observed at Isawa Fan in northern Japan, and modeled by hydrological equations. We solve the Richards equation numerically for the time variation in the vertical soil moisture distribution, which is then spatially integrated to estimate gravity changes due to the soil moisture distribution. In modeling Isawa Fan, we assume a simple hydrological model: a horizontally homogeneous soil in an infinite half-space. The estimated gravity is consistent with the observed gravity during a 50-day period within about 0.4 µgal root mean square, owing to both observed soil parameter values and the observation building geometry being incorporated into the hydrological model. However, the estimated gravity cannot fully reproduce annual gravity changes observed during a 2-year time frame, because the boundary conditions in the modeling determine only local water distributions and the resultant short-period gravity changes. Instead, the observed gravity over these 2 years can be reproduced within about 1.0 µgal root mean square, if the additional parameters of the annual gravity change (Aac and Aas) and the snowfall effect (As) are calculated by the function regression to the observed gravity with the least-squares method. The hydrological modeling techniques presented here can be utilized at all gravity sites in flat areas similar to Isawa Fan, such that hydrological effects in gravity data can be corrected and mass transfers associated with earthquakes and volcanoes can be monitored.

The design of temporary excavation support to Eurocode 7

This paper examines how Eurocode 7 relates to the design of temporary excavation support. It is shown that total stress design and the net available passive resistance method described in Ciria Report 104 can produce inconsistent results, which must be carefully checked for sensitivity to the soil parameter values used. Many temporary excavations are designed using moderately conservative soil parameter values and a limit equilibrium method of analysis with a lumped factor of safety of 1·5. It is concluded that design in accordance with Eurocode 7 produces higher propping forces than design using this approach, but that Eurocode 7 produces propping forces over 60% lower than design in accordance with Ciria Report C580.

Closed-form expressions for ground return impedances of overhead lines and underground cables

This paper presents an analysis of closed-form expressions for ground return impedance of overhead lines and underground cables. For the former an actual solution to Carson’s infinite integral is obtained via integral transformation techniques while for the latter an approximate expression based upon asymptotic expansion is presented. Numerical integration based upon Gauss-quadrature is performed for the comparison.Several test cases are presented considering different values for soil parameters. The results indicate that good accuracy was obtained. Limitations of the proposed expressions are also presented.

Comparative evaluation of modified neem leaf, neem leaf and woodash extracts on soil fertility improvement, growth and yields of maize (<i>Zea mays</i> L.) and watermelon (<i>Citrullus lanatus</i>) (Sole and Intercrop)

Two field experiments were carried out at Akure (7oN, 5o101E) in the rainforest zone of Nigeria in 2006 and 2007 to determine the effectiveness of neem leaf, woodash and modified neem leaf extracts as fertilizer sources in improving soil fertility, growth and yield of maize (Zea mays L) and watermelon (Citrulus lanatus) sole and intercrop. There were six treatments namely, poultry manure, neem leaf extract (sole), woodash extract, modified neem leaf (neem leaf + woodash), NPK 15-15-15 and a control (no fertilizer nor extract), replicated three times and arranged in a randomized complete block design (RCB). The extracts (neem leaf, wood ash and modified neem leaf) were applied at 1200 litres per hectare each, NPK 15-15-15 at 300 kg/ha and poultry was applied at 6t/ha. The results showed that there were significant increases (P 2O), K, Ca, Mg, Na, O.M, P and N compared to NPK 15-15-15 and neem leaf extract. For instance, modified neem leaf extract increased soil pH (H2O), K, Ca, Mg, Na, O.M, P and N by 12.4%, 32.8%, 25%, 23.7%, 19.32%, 17.24% and 20% respectively compared to neem leaf extract under intercrop plot. The high soil K/Ca, K/Mg and P/Mg ratios in the NPK 15-15-15 fertilizer treatment led to an imbalance in the supply of P, K, Ca and Mg nutrients to maize and watermelon crops. The least values for growth, yield and soil parameters were recorded under the control treatment. In these experiments, modified neem leaf extract (woodash + neem leaf extracts) applied at 1200 litres/ha was the most effective in improving soil fertility, growth and yield of maize and watermelon (sole and intercrop) and could substitute for 6 tons per hectare of poultry manure and 300kg/ha of NPK 15-15-15 fertilizer.

Aggregation Strategies for SSURGO Data: Effects on SWAT Soil Inputs and Hydrologic Outputs

The USDA-NRCS Soil Survey Geographic (SSURGO) dataset provides the most comprehensive, detailed soil data coverage across the United States. Correct usage of these data within a hydrologic model depends on assumptions that define how soil property data are aggregated. To reduce data intensity and improve model efficiency, most hydrologic modeling studies using SSURGO assume that soil property data are adequately grouped into some notion of a “soil type” which is represented by the map unit, denoted as map unit key (MUkey), within SSURGO. However, the map unit is not intended for this purpose as continuity in map unit design or composition is not guaranteed between adjacent surveys of different vintages. This causes problems when several survey areas are used together, because similar soils are assigned a different map unit across the boundaries of soil survey maps. We present a methodology for aggregating soil data among multiple soil survey areas according to soil taxonomic information available in SSURGO. Results indicate that the aggregation method provides an acceptable representation of soil parameter values and distributions while eliminating the reliance on an arbitrary map unit for soil type identification. The results of the hydrologic modeling using the Soil and Water Assessment Tool (SWAT) in the San Joaquin River Watershed indicate that the commonly used aggregation method and the newly developed method satisfactorily estimated soil and surface hydrologic processes as compared to using a non-aggregated soil dataset. For the soil hydrologic processes, the SWAT model output from our aggregation method accurately estimated soil water content (mean difference compared to the non-aggregated soil dataset output of −4 mm for western San Joaquin River Watershed subbasins and 15 mm for the eastern San Joaquin River watershed subbasins) and lateral flow (3 mm for the western subbasins and 0.2 mm for the eastern subbasins) as compared to using a non-aggregated soil dataset. For the surface hydrologic processes, the SWAT model under predicted surface runoff (−0.5 mm for the western subbasins and −0.1 mm for the eastern subbasins) and sediment yield (−0.02 t/ha for the western subbasins and −9×10−4 t/ha for the eastern subbasins) as compared to using a non-aggregated soil dataset. While some variations were statistically significant, the differences were numerically small. The results show that soil taxonomy provides a robust framework for grouping soils.

An extension of the Green-Ampt model to decreasing flooding depth conditions, with efficient dimensionless parametric solution

The theoretical formulation of the Green-Ampt infiltration model has been extended to conditions of decreasing flooding depth in an isolated system. By defining dimensionless variables of flooding depth s and time τ, an implicit dimensionless equation τ(s) was obtained, which contains a single fundamental dimensionless parameter γ controlling the process, named “infiltration delay parameter”. The characteristics and functional behaviour of γ were analysed, and its physical meaning discussed. A parametric expression s(τ) has been obtained, which uses a unique descriptive parameter a, which in turn depends only on γ and on four generic coefficients valid for a wide range of soil properties and conditions occurring in nature. By means of numerical simulations using different values of soil parameters and initial flooding depths, it was proved that the proposed parametric function generates similar infiltration rates and cumulative storages to those that are obtained starting from Darcy's equation in the extended Green-Ampt scheme. Citation Barrera, D. & Masuelli, S. (2011) An extension of the Green-Ampt model to decreasing flooding depth conditions, with efficient dimensionless parametric solution. Hydrol. Sci. J. 56(5), 824–833.

English

Lack of adequate topsoil depth and perception of lost soil fertility on pipeline construction rights-of-way are major concerns for landowners and can become extensive post-construction costs for pipeline companies. Reduction in crop productivity can occur in agricultural fields after pipeline construction due to numerous factors including compaction, drainage, and changes in surface soil characteristics. Significant changes in soil texture and/or organic matter content can change cation exchange capacity (CEC) and water holding capacity of the soil. Reduced CEC, as well as low soil fertility levels, can reduce the crops ability to withstand environmental stress, therefore reducing crop yield. Topsoil stockpiled and replaced on the construction right-of-way (ROW) of a 42-inch (107 cm) natural gas pipeline through Kansas and Missouri was evaluated and compared to the topsoil adjacent to the ROW. Soils were evaluated on and off the ROW to compare topsoil depths, soil fertility, texture and other agronomic factors. Varying amounts of topsoil loss were found at a majority of sample sites. Differences between the on-ROW and off-ROW values for the other soil parameters tested were not significant. The lack of significant change in tested parameters on-ROW, compared to the undisturbed topsoil off-ROW indicate no loss of crop yield potential would be expected due to the reduction in topsoil depth.

Characterization of the pre-AD 79 Roman paleosol south of Pompeii (Italy): Correlation between soil parameter values and paleo-topography

The Plinian eruption of Somma-Vesuvius AD 79 that destroyed the ancient city of Pompeii, resulted in a nearly complete burial of the Sarno River plain. Hence, to a certain extent the pre-AD 79 Roman paleo-surface and paleosols of that entire landscape were conserved. To characterize the pre-AD 79 Roman paleosol and the paleo-topographical situation south of Pompeii, ten stratigraphic core drillings were conducted along two transects stretching W–E and N–S. At five locations the drillings yielded Roman paleosols that were described, sampled and analysed for soil physical and chemical parameters. Corresponding to the present-day topography of the study area, which is flat to slightly sloping, the Roman paleo-surface appears in a similar relative paleo-topographic position. It runs nearly parallel to the modern surface at a depth of 5.50 to 6.40 m. By comparing the paleosol's properties with its position along the transects a correlation between soil parameter values and paleo-topography is revealed. The spatial distribution of paleosol characteristics is a function of soil development in relation to elevation and distance from the paleo-floodplain of the paleo-Sarno River network. This is most evident for soil thickness, soil horizonation, total organic carbon (TOC) and phosphate content and to some extent for soil texture and oxalate-extractable Si (Si ox) as a measure of allophane content. Near the paleo-Sarno River and its floodplain the Roman paleosols were 30 cm thick having an AC-profile and showed lower amounts of TOC and phosphates. In contrast, at higher elevation and longer distance from the paleo-River the paleosols were 60 cm thick, showed the development of a B-horizon, and had higher TOC and phosphate contents and partly a finer soil texture and higher amounts of Si ox. Nevertheless, all five Roman paleosols were macroscopically isotropic, i.e. they were mostly very dark gray throughout the profile. Thus, and in accordance with Al ox + 0.5Fe ox < 2%, at the time of the eruption AD 79, pedogenetically the Roman paleosol south of Pompeii is a relatively young soil. Subsequent to the eruption AD 79 at lower elevations the buried Roman paleosols have come under the influence of a seasonally fluctuating groundwater table. This caused redoximorphic features in the lower section of the AD 79 white pumice layer in terms of red Fe(III)-oxide accumulations and increased amounts of SO 4 2− in the underlying pre-AD 79 Roman paleosols.

Degradation of the soil physicochemical properties resulting from continuous logging of Gmelina arborea and Tectona grandis plantations

This study assessed the changes in soil properties in sites subjected to continuous logging in exotics plantation sites of Gmelina arborea and Tectona grandis with the aim to evaluate the deterioration level of the soil productivity in respect to human disturbance. Thirty five sampling plots, each measuring 40 m x 25 m were used for soil sampling. Standard field and laboratory methods were employed in the collection of data for 18 soil characteristics (sand, silt, clay, water holding capacity, electrical conductivity, bulk density, total porosity, pH, organic matter , total nitrogen, available phosphorus, exchangeable calcium, magnesium, potassium, sodium, exchangeable acidity, cation exchange capacity and base saturation) at depths of 0 - 15 cm and 15 - 30 cm. The results indicated that values of soil and plant parameters decreased with length of continuous logging (1, 5 and 10 years respectively). The soil deterioration indices of the logged plots showed high deterioration of all the soil properties except electrical conductivity, bulk density exchangeable acidity and in exchangeable sodium, percent silt and sand at both levels of soil depths. The two exotic species were impacted differently on the soil properties on the study area as a result of adverse logging. If these plots area are left to fallow for a considerable period of time, the lost soil nutrients may be replaced. Key words: Deterioration level, soil productivity, textural properties, electrical conductivity, Gmelina species, Tectona species, continuous logging and sustainable productivity.

Global sensitivity analysis measures the quality of parameter estimation: The case of soil parameters and a crop model

One common limitation of the use of crop models for decision making in precise crop management is the need for accurate values of soil parameters for a whole field. Estimating these parameters from data observed on the crop, using a crop model, is an interesting possibility. Nevertheless, the quality of the estimation depends on the sensitivity of model output variables to the parameters. The goal of this study is to explain the results for the quality of parameter estimation based on global sensitivity analysis (GSA). The case study consists of estimating the soil parameters by using the STICS-wheat crop model and various synthetic observations on wheat crops ( LAI, absorbed nitrogen and grain yield). Suitable criteria summarizing the sensitivity indices of the observed variables were created in order to link GSA indices with the quality of parameter estimation. We illustrate this link on 16 different configurations of different soil, climatic and crop conditions. The GSA indices were computed by the Extended FAST method and a function of RMSE was computed with an importance sampling method based on Bayes theory (GLUE). The proposed GSA-based criteria are able to rank the parameters with respect to their quality of estimation and the different configurations (especially climate and observation set) with respect to their ability to estimate the whole parameter set. They may be used as a tool for predicting the performance of different observation datasets with regard to parameter estimation.

Ecohydrology of groundwater‐dependent ecosystems: 2. Stochastic soil moisture dynamics

In groundwater‐dependent ecosystems, interactions between rainfall, water table fluctuations, and vegetation are exerted through the soil water content. The dynamics of soil moisture, in fact, are strongly coupled to fluctuations of the water table and, together, they control the overall ecosystem dynamics. We propose here a simple process‐based stochastic model for the study of soil moisture dynamics at a generic depth, to complement the stochastic model of water table depth presented in the companion paper. The model presented here is based on a local and depth‐dependent water balance driven by stochastic rainfall (marked Poisson noise) and accounting for processes such as rainfall infiltration, root water uptake, and capillary rise. We obtain a semianalytical formulation of the stationary probability distribution of soil water content at different depths, which is studied for different values of soil, climate, and vegetation parameters. The probability distributions are used to investigate the ecohydrology of groundwater‐dependent ecosystems, including the quantitative description of the vegetation–water table–soil moisture interplay and the probabilistic analysis of root water uptake.

Identifying parameters controlling soil delayed behaviour from laboratory and in situ pressuremeter testing

AbstractThe aim of this paper is to present a methodology for identifying the soil parameters controlling the delayed behaviour from laboratory and in situ pressuremeter tests by using an elasto‐viscoplastic model (EVP‐MCC) based on Perzyna's overstress theory and on the elasto‐plastic Modified Cam Clay model. The influence of both the model parameters and the soil permeability was studied under the loading condition of pressuremeter tests by coupling the proposed model equations with Biot's consolidation theory. On the basis of the parametric study, a methodology for identifying model parameters and soil permeability by inverse analysis from three levels of constant strain rate pressuremeter tests was then proposed and applied on tests performed on natural Saint‐Herblain clay. The methodology was validated by comparing the optimized values of soil parameters and the values of the same parameters obtained from laboratory test results, and also by using the identified parameters to simulate other tests on the same samples. The analysis of the drainage condition and the strain rate effect during a pressuremeter test demonstrated the coupled influence of consolidation and viscous effects on the test results. The numerical results also showed that the inverse analysis procedure could successfully determine the parameters controlling the time‐dependent soil behaviour. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Soil loss tolerance limits for planning of soil conservation measures in Shivalik–Himalayan region of India

Abstract Soil loss tolerance limit is defined as the threshold upper limit of soil erosion that can be allowed without degrading long term productivity of specific soils. In India a default soil loss tolerance limit (SLTL) of 11.2 Mg ha − 1 yr − 1 is followed for planning soil conservation activities. The objective of this investigation is to provide a methodology to estimate quantitative SLTL for the Shivalik–Himalayan region in India for suggesting suitable soil conservation measures. A quantitative model was used to integrate potential soil indicators such as infiltration rate, bulk density, water stable aggregate, organic carbon and fertility status to assess soil quality governing soil resistibility to erosion. Scaling functions were used to convert soil parameters to unit less 0 to 1 scale. Normalized values of soil parameters were then multiplied by assigned weights based on relative importance and sensitivity analysis of each indicator. Soils were grouped into 1, 2 and 3 depending on overall additive score. A general guideline developed by the USDA-Natural Resource Conservation Service (NRCS) was followed with certain modifications in depth category for estimation of SLTLs. Soil loss tolerance limits varied from 2.5 to 12.5 Mg ha − 1 yr − 1 compared to single value of 11.2 Mg ha − 1 yr − 1 being followed earlier. Consideration of the newly estimated SLTLs would facilitate site specific conservation planning and prioritising areas for watershed management activities in India.

Further insight into the behaviour of Pleistocene Osaka clays at KIA Phase 1 island

The behaviour of the Pleistocene Osaka clays at Kansai International Airport Phase 1 island is investigated by FEM analyses using an elasto-viscoplastic constitutive model which replicates the destruction processes occurring in the microstructure of the clay. Excellent predictions are obtained by 2D analyses carried out using the actual soil profile and the characteristic values of soil parameters, confirming the validity of the methods proposed for characterizing and modelling structured clays. Unlike 1D analyses, where partially effective drainage layers occur, 2D analyses do not require arbitrary pre-definition of the model drainage scenario and of the ‘equivalent’ permeability of interlayered clays to account for macrostructure. In these conditions, 1D analyses must be validated with reference to 2D or 3D prototype analyses and/or well documented experience of comparable work. Once thus validated, 1D analyses are used to investigate the relative merits of possible measures (relief wells, preloading, lightweight fill) aimed at reducing in-service settlement. For future reclamation works at sites where structured clays extend to great depth, filling with lightweight material shows the greatest promise, but it is unlikely to remove the need for designing the superstructure to accommodate the inevitable settlement, which requires accurate prediction.

Assessment of nutritional status of soil supporting coconut (Cocus nucifera) cultivation in some localities of Edo State of Nigeria

Coconut cultivation and information on the nutritional status of soils and fertilizers recommendations for its cultivation are limited in Nigeria. Since a high yield of coconut is related to the fertility status of the soil, a study was conducted to evaluate the status of soils supporting coconut cultivation. The evaluation of the surface soil (0 – 15 cm) and the subsoil (15 – 30 cm) of seven localities showed that the average pH was 5.75 ± 0.21 and 5.51 ± 0.15, respectively, indicating that the subsoil was slightly acidic than the surface soil. Highest values for the surface soil parameters were found to be 0.58 ± 0.08 gkg-1 for exchangeable acidity, 2.55 ± 0.02 gkg-1 for organic carbon (C), 0.13 ± 0.02 gkg-1 for total nitrogen (N), 20.24 ± 1.10 gkg-1 for the carbon : nitrogen ratio, 17.45 ± 0.60 for available phosphorus (P), 0.21 ± 0.02 Cmolkg-1 for sodium (Na), 0.14 ± 0.01 Cmolkg-1 for potassium (K), 2.91 ± 0.10 Cmolkg-1 for calcium (Ca) and 0.79 ± 0.06 Cmolkg-1 for magnesium (Mg). On the other hand, the subsoil parameters were 0.74 ± 0.15 gkg-1 for exchangeable acidity, 1.85 ± 0.03 gkg-1 for organic C, 0.09 ± 0.01gkg-1 for total N, 19.69 ± 0.67 gkg-1 for the carbon : nitrogen ratio, 10.15 ± 0.38 for available P, 0.16 ± 0.01 Cmolkg- 1 for Na, 0.09 ± 0.01 Cmolkg-1 for K, 1.59 ± 0.04 Cmolkg-1 for Ca and 0.46 ± 0.04 Cmolkg-1 for Mg. The results showed the samples were not generally ideal for coconut growth and production of good yields because of marginal deviation from acceptable limits. It is recommended that the soils in these localities need fertilization especially with nitrogen and potassium carriers for the purpose of coconut cultivation.

Earthquake ground motion simulation with frequency-dependent soil properties

A one-dimensional earthquake ground motion simulation with frequency-dependent dynamic soil parameters, which include shear wave velocity and quality factor, is performed within the frequency band between 10 −2 and 30 Hz. For the simulation, the general frequency-dependent dynamic soil properties are obtained by using a new non-resonance technique on various soils. Comparisons between transfer functions involving frequency-dependent and -independent dynamic soil parameters indicate that soil amplification throughout the considered frequency range is sensitive to the values of the dynamic soil parameters, in particular to the quality factor. Simplification of frequency-dependent dynamic soil parameters into constants, which prevail as a convenient practice, incurs large amplitude distortion. This study therefore demonstrates that the dynamic properties of soils play an important role in the near surface earthquake ground motion analyses and need to be used in the same way as how they were measured.

Quantifying sensitivity of local site response models to statistical variations in soil properties

We perform a combined stochastic-deterministic analysis of local site response using two computer codes, an equivalent linear analysis program SHAKE and a fully nonlinear finite element code SPECTRA. Our goal is to compare the relative sensitivity of the two codes to statistical variations in soil properties. For the case studies, we re-analyze two ground motion records in Lotung, Taiwan, and one ground motion record in Gilroy, California, utilizing the recorded ground motions at the site deterministically as input into the two codes while treating the uncertain soil parameters as random variables. We then obtain empirical cumulative distribution functions of the Arias intensity and acceleration spectrum intensity, two measures of cumulative damage, to compare the relative sensitivity of the two codes to variations in model parameters. We show that the two codes exhibit comparable sensitivities to statistical parameter variations, indicating that even in the presence of fluctuations in the soil parameter values it is possible to pursue a fully nonlinear site response analysis with SPECTRA and benefit from its superior accuracy.

Species richness and environmental correlates in deciduous forests of Northwest Germany

The hump-backed curve is a well-known model to explain the local variation in plant species richness and predicts highest species numbers at intermediate productivity levels. To test the validity of this model we studied various types of deciduous forest in Northwest Germany in regard to the relation between species richness and environmental factors. We recorded species numbers at three different scales in totally 48 sites and determined productivity, values of soil parameters and light conditions in all sites. Our data showed that the hump-backed model in fact best explained the relationship between species richness and productivity on a local scale. Also the relationship between species richness and several soil factors (pH, P, Ca and C/N) was best described by a unimodal curve. The amount of variation explained decreased from the largest plot size (100 m 2) to the smaller plot sizes (10 and 1 m 2). We developed multivariate models for the prediction of species richness by dividing the data set into a training and a test data set for generating and testing of the models. The most important variables in the multiple models were C/N, pH and productivity. The predictive abilities of the best models were fairly high, but there was still much unexplained variation in the relation between observed and expected species richness. The remaining variation could partly be explained by factors related to the habitat configuration of the sites (patch size and isolation).

Effects of terracing afforestation with Pinus sylvestris L. on the physical soil properties in the Iberian Range of Soria

The methodology previously used to study the afforestations by terraces with Pinus sylvestris L. in Castilla y León is extended in this paper to study in more detail the impact on physical soil properties of the afforestations by terraces with Scots pine in the northern area of the Iberian Range of Soria. The values of soil parameters are obtained from 5 profile types: non-afforested, next to the cutting, next to the embankment, between terraces and in Scots pine mature stands, located in seven plot series, and then compared. The soil parameters are evaluated as follows: fine earth, sand, silt and clay, both in the whole profile and in the upper layer of the profile, permeability, equivalent moisture and water holding capacity of the soil profile, and erodibility. After 16-17 years, no significant changes have occurred in the physical properties that define the soil habitat of the Pinus sylvestris in Spain. Significant fine particle retention, nonoutstanding decrease of permeability, considerable improvement of water holding capacity, no increase of erodibility and progress toward ecological conditions similar to the soils with mature stands are detected, with values within those of the present central habitat of the species in Spain. Regarding to the changes in the soil physical properties, this method result appropriate for afforesting with Pinus sylvestris the above-mentioned region.

AN AGGREGATED FUZZY RELIABILITY INDEX FOR SLOPE STABILITY ANALYSIS

While sophisticated analytical methods like Morgenstern-Price or finite element methods are available for more realistic analysis of stability of slopes, assessment of the exact values of soil parameters is practically impossible. Uncertainty in the soil parameters arises from two different sources: scatter in data and systematic error inherent in the estimate of soil properties. Hence, stability of a slope should be expressed using a factor of safety accompanied by a reliability index. In this paper, the theory of fuzzy sets is used to deal simultaneously with the uncertain nature of soil parameters and the inaccuracy involved in the analysis. Soil parameters are defined using suitable fuzzy sets and the uncertainty inherent in the value of factor of safety is assessed accordingly. It is believed that this approach accounts for the uncertainty in soil parameters more realistically compared to the conventional probabilistic approaches reported in the literature. A computer program is developed that carries out the large amount of calculations required for evaluating the fuzzy factor of safety based on the concept of domain interval analysis. An aggregated fuzzy reliability index (AFRI) is defined and assigned to the calculated factor of safety. The proposed method is applied to a case study and the results are discussed in details. Results from sensitivity analysis describe where the exploration effort or quality control should be concentrated. The advantage of the proposed method lies in its fast calculation speed as well as its ease of data acquisition from experts' opinion through fuzzy sets.