Faculty Publications
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Item Predictions of two popular closed-form models for unsaturated hydraulic conductivity (K) are compared with in situ measurements made in a sandy loam field soil. Whereas the Van Genuchten model estimates were very close to field measured values, the Brooks-Corey model predictions were higher by about one order of magnitude in the wetter range. Estimation of parameters of the Van Genuchten soil moisture characteristic (SMC) equation, however, involves the use of non-linear regression techniques. The Brooks-Corey SMC equation has the advantage of being amenable to application of linear regression techniques for estimation of its parameters from retention data. A conversion technique, whereby known Brooks-Corey model parameters may be converted into Van Genuchten model parameters, is formulated. The proposed conversion algorithm may be used to obtain the parameters of the preferred Van Genuchten model from in situ retention data, without the use of non-linear regression techniques.(Elsevier, Field evaluation of unsaturated hydraulic conductivity models and parameter estimation from retention data) Nandagiri, L.; Prasad, R.1996Item The soil moisture characteristic (SMC) forms an important input to mathematical models of water and solute transport in the unsaturated-soil zone. Owing to their simplicity and ease of use, texture-based regression models are commonly used to estimate the SMC from basic soil properties. In this study, the performances of six such regression models were evaluated on three soils. Moisture characteristics generated by the regression models were statistically compared with the characteristics developed independently from laboratory and in-situ retention data of the soil profiles. Results of the statistical performance evaluation, while providing useful information on the errors involved in estimating the SMC, also highlighted the importance of the nature of the data set underlying the regression models. Among the models evaluated, the one possessing an underlying data set of in-situ measurements was found to be the best estimator of the in-situ SMC for all the soils. Considerable errors arose when a textural model based on laboratory data was used to estimate the field retention characteristics of unsaturated soils.(ASCE - American Society of Civil Engineers, Relative performances of textural models in estimating soil moisture characteristic) Nandagiri, L.; Prasad, R.1997Item Effect of pH on the geotechnical properties of laterite(2006) Sunil, B.M.; Nayak, S.; Shrihari, S.Environmental Geotechnology has emerged as an interdisciplinary science, aiming and forecasting, analyzing and solving the geotechnical problems involving the influence of environmental factors. Lateritic soil of west coast region of India was studied to investigate the effect of soaking on the engineering properties and chemical characteristics of soil, soaked in different pH solutions (pH = 5.0, pH = 7.0, pH = 8.0). 12 N hydrochloric acid and 15 M ammonia solution were used to monitor the pH of the solution for about ninety days. Results showed that the pH of the solution has strong influence on the chemical characteristics of lateritic soil. The engineering properties of soil are altered when compared with the initial characteristics of the soil. The reason for this observed behavior of the soil is addressed in this paper. © 2006 Elsevier B.V. All rights reserved.Item Strength behaviour of geogrid reinforced shedi soil subgrade and aggregate system(2006) Ravi Shankar, A.U.R.; Suresha, S.N.Shedi soil (Lithomargic clay), a yellowish-white silty soil underlying lateritic soil, is densely deposited along Konkan belt of India. The strength behaviour of Shedi soil under varying moisture content is major problem for road construction projects in this region. In the present investigation, the subgrade is stabilized with geogrid, keeping the geogrid at different positions from top of subgrade, to locate its optimum position. The plate load tests were also conducted at soaked and unsoaked conditions for unreinforeced, reinforced (with Geogrid) subgrade with aggregate base course. An equation has been established based on load-deflection values recorded for subgrade of un-reinforced and reinforced with geogrid at different levels. The deflection values obtained from equation and from the laboratory investigation were compared. In the case of reinforced subgrade with aggregate base course, the theoretical deflection values were computed based on Burmister's theory and compared with laboratory deflection values.Item Hydraulic and compaction characteristics of leachate-contaminated lateritic soil(2007) Nayak, S.; Sunil, B.M.; Shrihari, S.Large quantities of leachate-contaminated lateritic soil results from dump yards in the southwest coast of India. These dump yards receive large quantities of municipal solid waste which includes chemical, industrial and biomedical wastes. Large areas of land are currently being used for this purpose. An extensive laboratory testing program was carried out to determine the compaction characteristics and hydraulic conductivity of clean and contaminated lateritic soil. Batch tests were used to study the immediate effect of leachate contamination on the properties of lateritic soil. Contaminated specimens were prepared by mixing the lateritic soil with leachate in the amount of 5%, 10% and 20% by weight to vary the degree of contamination. The results indicated a small reduction in maximum dry density and an increase in hydraulic conductivity due to leachate-contamination. The change induced by chemical reaction in the microstructure of the soil was studied by scanning electron microscope before and after contamination of soil with leachate. The structure of the leachate contaminated soil sample appeared to be aggregated in scanning electron microscope analysis. The aggregated structure increases the effective pore space and thus increases the hydraulic conductivity. Fifty percent increase in hydraulic conductivity was observed for specimens prepared at standard Proctor density and mixed with 20% leachate. Compaction characteristics did not change much with the presence of leachate up to 10%. With 20% leachate the maximum dry density decreased slightly indicating excess leachate in the soil. However the changes are not significant. © 2007 Elsevier B.V. All rights reserved.Item Effect of soil parameters on dynamic cone penetration indices of laterite sub-grade soils from India(2009) George, V.; Nageshwar Rao, Ch.; Shivashankar, R.The focus of this study was on correlating the effect of grain-size, maximum dry-density (MDD), field moisture content, and the void ratios on penetration measured using the dynamic cone penetrometer (DCP) for laterite soils blended with fines. Tests were performed on soil samples compacted to MDD for moulding water contents set to the optimum moisture content (OMC), dry of OMC, and wet of OMC un-soaked condition. The results indicated that an increase in the fines-content caused a decrease in the MDD, and an increase in the OMC and the DCP penetration. Regressions were developed correlating various parameters. © Springer Science+Business Media B.V. 2008.Item Shear strength characteristics and chemical characteristics of leachate-contaminated lateritic soil(2009) Sunil, B.M.; Shrihari, S.; Nayak, S.Leachate is a hazardous liquid and is a major cause of concern in landfills. Numerous environmental problems such as soil and groundwater contamination occur in unlined landfills due to free flow of leachate. Large quantities of leachate-contaminated soils result from open dumping in the study area. These dump yards receive large quantities of municipal solid waste which includes chemical and industrial wastes. Large areas of land are currently being used for this purpose. An extensive laboratory testing program was carried out to determine the properties of clean and contaminated lateritic soils. Laboratory prepared municipal solid waste leachate was used in this study. Contaminated specimens were prepared by mixing the soils with MSW leachate in the increments of 0%, 5%, 10% and 20% by weight to vary the degree of contamination. The results showed that the MSW leachate affects the Atterberg limits, shear strength and chemical characteristics of the lateritic soils. The liquid limit and the plasticity index of the lateritic soils increases with MSW leachate concentration. For specimens tested at the Proctor density, effective cohesion increases and effective friction angle decreases due to increase in leachate concentration. This is attributed due to the increase in clay content of lateritic soil after interaction with the leachate. This led to increase in cohesion parameter and the friction angle decreases. The pH measurements of lateritic soil contaminated with MSW leachate indicated an increase in pH values. This is also accompanied by slight increase in the cation exchange capacity of the soil. The change in chemical characteristics of lateritic soil contributed due to addition of leachate may be detrimental to foundation concrete in real field conditions. The present work deals with an attempt to study the effect of leachate on the Atterberg limits, shear strength properties and chemical characteristics of lateritic soil. © 2009 Elsevier B.V. All rights reserved.Item Importance of geology and soil survey for mobile communication site planning using RS/GIS technology(2010) Naveenchandra, B.; Lokesh, K.N.; Usha; Gangadhara Bhat, H.G.Geology and Soil survey constitutes a valuable resource inventory linked with the survival of life on the earth. The technological advancements in the field of remote sensing and Geographical Information System have been a boon for such surveys. The present paper describes the role of Remote sensing and Geographical Information System (GIS) technologies for geological mapping and characterizing the importance of soils at various scales for identification of suitable sites for mobile communication network. Cellular network design is becoming more and more important since the network quality is highly dependent on the distribution of base stations. To design a cellular network for a particular region efficiently and accurately, the site suitability is an important determination. The country's mobile services market is forecast to grow by a compound annual rate of 28.3% in next five years. India is a vibrant market from communications point of view. The subscriber base in the wireless market in India, the world's fastest growing telecom market reached another milestone when it surpassed 200 million subscribers in Aug 2008. At present there are around 54000 cell sites operated by different GSM/CDMA operators. This number would further go up to 80,000 in next couple of years. To serve an increasing number of users requires an increasing number of base stations. Thus, operators must carefully plan the deployment and configurations of radio base stations to support voice and data traffic at a level of quality expected by customers. The present study carried out in the Udupi district of Karnataka State based on IRS 1C/1D LISS-III and CARTOSAT-1 satellite data. Various thematic maps like geology, soil, geomorphology, slope and land use/land cover with DEM has helped in understanding the terrain in a better way. The multi spectral satellite data in conjunction with SuperGIS, SuperPad and Getac GPS hardware have helped to formulate suitable plans and strategies for an effective Telecom planning and development in Udupi district. © 2010 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.Item Impact assessment of watershed development programme - A case study of Itagi watershed(2010) Palakshappa, K.; Nagaraj, M.K.; Shivapur, A.V.Soil, water and vegetation are the important gifts of nature to mankind. Welfare and development of mankind and its civilization revolves around conservation and development of these vital natural resources, which are so interdependent that one can not be managed efficiently without the other two. Watershed Development Programs (WDP) going on in India basically as soil and water conservative programs (as a policy response to the increasing environmental crisis and non-sustainability of agriculture especially in the dry land/semi-arid regions) has modified substantially with the introduction of watershed guidelines in 1994 by the Government of India. In the present study the area considered for assessment is Itagi sub watershed in Ranebennur taluk, Haveri district, Karnataka. During the watershed development programme soil and water conservation structures were constructed in the study area in the year 2004. The analysis of data reveals that there is an improvement in the groundwater recharge, increase in yield of the wells, increase in agricultural production, reduction in soil erosion and many other tangible and intangible benefits as a result of this watershed development programme. © 2010 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.Item Interactions Between Soils and Laboratory Simulated Electrolyte Solution(2010) Nayak, S.; Sunil, B.M.; Shrihari, S.; Sivapullaiah, P.V.To study the impact of salt water intrusion on two types of soils from west coast region of India were investigated in the laboratory. The key characteristics evaluated included Atterberg limits, compaction characteristics, hydraulic conductivity and chemical characteristics of selected soils. The sea at this coast receives effluent from different points and hence the characteristics change with time and locality. Therefore, to maintain uniform composition, 0.5 N sodium chloride solution (NaCl) was prepared in the laboratory and batch tests were used to determine the immediate effect on soils. Soil specimens were prepared by mixing the soils with 0.5 N NaCl in the increments of 0, 5, 10 and 20% by weight to vary the degree of contamination. Experimental results of soils mixed with 0.5 N NaCl showed that the maximum dry density increases and the optimum moisture content (OMC) decreases with increasing sodium chloride concentration. The study also revealed that the hydraulic conductivity of the soils tested increases with increase in sodium chloride concentration. The Atterberg limits of contaminated specimens show a remarkable change when compared with uncontaminated specimens. © 2010 Springer Science+Business Media B.V.