The Application of Semi Variogram and Ordinary Kriging in Determining the Cohesion and Clay Percentage Distribution in Hilly Area of Sabah, Malaysia

Ordinary Kriging (OK) is one of the geostatistical methods, which were used in the variation types of mapping, which related to the soil. Compliment by semi variogram models, OK has become one of the most sought out method for the digital mapping, which applied Geographical Information System (GIS) as a main approach. Four semi variogram models, which are spherical, exponential, circular and gaussian would be applied to determine the best model for the mapping purposes, with Root-Mean-Squared-Error (RMSE) as a performance indicator. The value of the cohesion and clay percentage will be based according to the related depth. Each semi variogram model will be applied to determine the best model for each depth, whether it is cohesion or clay percentage, and producing a map, as a result. This mapping would be an alternative to the geological mapping, whereby it would show the range of the cohesion and clay percentage values rather than soil types.

Caracterização Física e Mineralógica de Materiais Intempéricos na Área Urbana de Juiz de Fora – MG, através de Análise Macroscópica, Difratrômetro de Raios-X (DRX) e Microscópio Eletrônico de Varredura (MEV)

Materiais saprolíticos constituem importantes seções no recorte vertical da paisagem. São materiais ainda pouco conhecidos e demandam maior dedicação. Para caracterização destes materiais pode-se fazer uso de técnicas mineralogia e micromorfologia como a difração de Raios-X (DRX) e o Microscópio Eletrônico de Varredura (MEV). O DRX é uma técnica de caracterização de estruturas cristalinas. O MEV é um tipo de microscópio capaz de produzir imagens de alta resolução da superfície de materiais sólidos. O objetivo é caracterizar amostras de materiais intemperizados de diferentes rochas. Foram selecionados cinco perfis de intemperismo em Juiz de Fora - MG. Os parâmetros utilizados para a análise física e mineralógica foram os seguintes: cor, textura, consistência, rocha de origem e grau de alteração, mineralogia e micromorfologia. A cor é variável entre e intra amostras, é dependente dos minerais constituintes e do grau de alteração. A textura está ligada aos minerais constituintes e seus tamanhos, que são dependentes de seus graus de alteração. A consistência é dependente da resistência dos minerais constituintes e da alteração. As rochas de origem são o quartzito ou o gnaisse. Os principais minerais encontrados foram quartzo, biotita, muscovita e caulinita. Quanto maior a porcentagem de argila, menor a consistência e maior o grau de alteração. A presença de minerais mais resistentes tende a dificultar a pedogênese, resultando em perfis mais arenosos, com poucos minerais de argila e sem atividade biológica. Nos perfis em que predomina o quartzo, apesar da presença desse mineral, o grau de alteração é elevado. Physical and Mineralogical Characterization of Weathering Materials in the Urban Area of Juiz de Fora - MG through Macroscopic Analysis, X-Ray Diffractometer and Scanning Electron Microscope ABSTRACTSaprolitic materials are important sections in the vertical cutout of the landscape. These materials are still little known and demand greater dedication. To characterize these materials, we can use mineral and micromorphological techniques such as X-ray diffraction, a technique for characterizing crystalline structures and the Scanning Electron Microscope, a type of microscope capable of producing high-resolution images of the surface of solid materials. The objective is to characterize weathered colors of different stones. Five weathering profiles were selected in Juiz de Fora - MG. The parameters used for physical and mineralogical analysis were as follows: color, texture, consistency, original rock and degree of change, mineralogy and micromorphology. The color is variable, depends on the constituent minerals and the degree of change. The texture is linked to the constituent minerals and their sizes, which depend on their degree of change. The consistency is dependent on the strength of the constituent minerals and the degree of change. The original rocks are quartzite and gneiss. The main minerals found were quartz, biotite, muscovite and kaolinite. The higher the clay percentage, the lower the consistency and the greater the degree of change. The presence of more resistant mineralsmakes pedogenesis difficult, resulting in more sandy profiles, with few clay minerals and without biological activity. In profiles that predominate quartz, despite the presence of this mineral, the degree of change is high.Keywords: Mineralogy; Micromorphology; Weathering material.

An experimental investigation of the influence of plasticity on creep degradation rate

Intrinsic soil properties, such as the Atterberg limits, are essential factors influencing the mechanical behaviour of the fine-grained soils. In this study, a series of long-term multiple-stage loading oedometer tests were performed on alluvial organic soils to investigate the creep behaviour. The plasticity ratios ranged from 0.4 to 0.63. The smaller value of the plasticity ratio Rp indicated higher soil plasticity. The results showed that the coefficient of secondary compression Cαe of alluvial organic soils was stress- and strain-rate-dependent. The coefficient of secondary compression change index m was derived using a double-logarithmic approach for a creep degradation and was related to the plasticity and clay percentage to fines. Based on the results, it was found that high plasticity soils exhibit slow creep degradation rate during one-dimensional straining under normally consolidated state. The results show that the higher soil plasticity expressed by the plasticity index, plasticity ratio and clay percentage to fines, smaller the coefficient of secondary compression change index. Moreover, the correlations among a soil plasticity properties and creep parameters for the alluvial soils have also been proposed.

A new empirical viscosity model for composed suspensions used in experiments of sediment gravity flows

ABSTRACT Sediment gravity flows are natural flows composed by water and sediment in which the gravitational flow acts on the sediment. The distinct physical properties of the cohesive (clay) and non-cohesive (sand) sediment, and the interaction between these particles alter the ability of the flow to resist to the movement (rheology) along time and space, represented by the viscosity of a mixture suspension. Hence, we propose to study the rheological properties of those mixtures and calculate their relative viscosity when used in the physical simulation of turbidity currents. Rheological tests were performed with various mixtures composed by water, clay and/or coal. Two equations are proposed to estimate the relative viscosity as a function of volume concentration of each sediment, the maximum packing fraction and the percentage of clay present in the mixture. The results also show an error close to 20% comparing similar models from the literature, which are satisfactory. The results also demonstrate that caution should be exercised when generalizing the use of a single model to predict the relative viscosity of suspensions. The influence of density (ρ), grain shape, clay percentage (Cclay), volumetric concentration (ϕ) and maximum packaging fraction (ϕmax) should be considered in the formulation of the equations.

SOIL ERODIBILITY AND SOIL SUSCEPTIBILITY TO EROSION BY WATER IN SHONKOLA MOUNTAINOUS AREA OF SORO DISTRICT, ETHIOPIA

Although the problem of soil erosion is common in all countries, it is one of the more persisting hazards in developing countries like Ethiopia which is a country located in tropic where there is higher precipitation and is vulnerable to almost all forms of environmental degradation which is also resulted from poor resource conservation practices. The main objective of this study is to determine soil erodibility and susceptibility to soil erosion in Shonkola mountainous area, Soro district. To determine soil erodibility and susceptibility to soil erosion, the percentage of primary soil separates (silt, very fine sand, and clay); percentage of organic matter; soil structure classes; and soil permeability were estimated. Soil samples were collected from 56 locations at an average depth of 15 cm to employ soil texture nomograph. Thus, soil erodibility of Shonkola area is determined and mapped to envisage the area that is highly susceptible for soil erosion. The soil erodibility value ranges from 0.01426 to 0.04001. It was found that the soil erodibility increases as organic content decreases, soil texture becomes finer and less permeable, and structure becomes poor. Prediction of soil erodibility and susceptibility to soil erosion is of great importance for soil erosion quantification, using GIS. The farm-unit level identification of soil types and existing specific problems are crucial in planning and implementation of any soil management strategies.

Evaluation and Development of Pedotransfer Functions for Predicting Saturated Hydraulic Conductivity for Mexican Soils

In the present work, we evaluate the prediction capability of six pedotransfer functions (PTFs), reported in the literature, for the saturated hydraulic conductivity estimations (KS). We used a database with 900 measured samples obtained from the Irrigation District 023, in San Juan del Rio, Queretaro, Mexico. Additionally, six new PTFs were constructed for KS from clay percentage, bulk density, and saturation water content data. The results show, for the evaluated models, that one model presents an overestimation for KS > 0.5 cm h−1 values, three models have an underestimation for KS > 1.0 cm h−1, and two models have a good correlation (R2 > 0.98) but more than three parameters are necessary. Nevertheless, the last two models require 3–4 parameters in order to obtain optimization. On the other hand, the models proposed in this work have a similar correlation with fewer parameters. The fit is seen to be much better than using the existing ones, achieving a correlation of R2 = 0.9822 with only one variable and R2 = 0.9901 when we use two.

Evaluation and Development of Pedotransfer Functions for Predicting Saturated Hydraulic Conductivity for Mexican Soils

In the present work, we evaluate the prediction capability of six Pedotransfer functions (PTFs), reported in the literature, for the saturated hydraulic conductivity estimations (Ks). We used a database with 900 measured samples obtained from the Irrigation District 023, in San Juan del Rio, Queretaro, Mexico. Additionally, six new PTFs were construct for Ks from clay percentage, bulk density and saturation water content data. The results show, for the evaluated models, that one model present an overestimation for Ks>0.5 cm h-1 values, three models have a underestimation for Ks>1.0 cm h-1 and two models have a good correlation (R2>0.98) but are necessary more than three parameters. Nevertheless, the last two models requires from three to four parameters in order to get the optimization. By other hand, the models proposed in this work have a similar correlation with a less number of parameters: the fit is seen to be much better than using the existing ones, achieving a correlation of R2 = 0.9822 with only one variable and a R2 = 0.9901 when we use two.

Application of modern methods: modeling of sedimentary soil ESP content

Knowing the exchangeable sodium percentage (ESP) variations and its values in sodic or saline-sodic soils is essential in order to estimate the amount of soil amendments and better land management. ESP calculated from cation exchange capacity (CEC), and since CEC measurement is difficult and time-consuming, ESP computation is costly and subject to error. Thus, presenting a method to estimate ESP indirectly, by an easily available index is much more efficient and economical. In this study, 296 soil samples collected and analyzed from Sistan plain, southeastern Iran. Soil ESP were predicted by using artificial neural networks (ANNs), comprising radial basis functions (RBFN) and multilayer perceptron (MLP) and adaptive neuro-fuzzy inference systems (ANFIS), and results compared with stepwise linear regression (SLR) method. Results indicated that the SLR models performed poorly in order to estimate ESP (R2 ≤ 0.58 and root mean square error (RMSE ≥ 4.31). Applying fewer inputs (electrical conductivity (EC and pH), ANFIS showed better results (R2=0.80, RMSE=2.34), while increasing inputs (clay and organic carbon) decreased the accuracy (R2=0.82, RMSE=4.20). Using more inputs, RBFN resulted in better performance in comparison with other methods (R2=0.83, RMSE=2.85). Sensitivity analysis using the connection weight method demonstrated that EC, pH, clay percentage and bulk density are the most important variables in order to explain ESP variability in the region, respectively. Generally, considering the evaluation criteria and the number of used variables of models, ANFIS (with EC and pH as inputs) is the most appropriate method for estimating ESP in Sistan plain.