Faculty Publications
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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 Microfabric and mineralogical studies using sem and xrd on the lithomargic clay stabilized with cement and quarry dust(CAFET INNOVA Technical Society 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2011) Sarvade, P.G.; Nayak, S.The infrastructural development activities due to rapid urbanization, low lying agricultural and marshy lands in and around Mangalore (India) are being converted into estates with locally available lithomargic clay. These filled up areas pose problems of low bearing capacity as well as excessive settlements. As long as this soil is confined and dry, there is a very little or no problem, when it comes in contact with water, it loses its strength. The engineering properties of this soil are enhanced by the addition of additives (cement, quarry dust and quarry dust +cement). In the present study the microfabric and mineralogical aspects of the stabilized lithomargic clay is studied using Scanning Electron Microscope (SEM) and X-ray diffractometer (XRD). The XRD analysis of lithomargic clay stabilized with cement, revealed the formation ettringite, CSH and CAH. The SEM analysis revealed change in the soil structure due to the addition of cement and quarry dust. © 2011 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.Item Geotechnical characteristics of lithomargic clay blended with marine clay as landfill liner material(CAFET INNOVA Technical Society cafetinnova@gmail.com 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2012) Allamaprabhu, K.; Sunil, B.M.; Nayak, S.; Fernandes, S.; Zafar, M.This paper reports a series of laboratory tests conducted on lithomargic clay (shedi soil), which is widespread over part of southwest coast of India, to assess whether it could be used as compacted clay liner for hydraulic barriers in engineered landfill. In order to assess the suitability of lithomarge as a barrier material, following tests such as index properties, compaction characteristics, hydraulic conductivity and unconfined compressive strength of the soil were conducted in the laboratory. From the studies, it is found that lithomargic soil is near to the recommended specifications for soils to be used as liner material. Suitable materials for soil liners are then obtained by blending different types of locally available soils to achieve the required low hydraulic conductivity and good strength. To achieve specifications for the liner material lithomargic clay is blended with 15% and 20% marine clay by weight of lithomargic clay. From standard compaction control, the blended soil shows hydraulic conductivity lower than the 1x10-7 cm/s. Acceptable zones (AZ) are constructed on the compaction plane to meet design objectives for hydraulic conductivity. It's strength properties show that the soil possesses higher strength than the recommended minimum strength of 200kPa, to support the overburden pressure imposed by the waste body. From the laboratory test results, it can be concluded that lithomargic clay blended with marine clay satisfies the requirements for a good soil liner material. © 2012 CAFET-INNOVA TECHNICAL SOCIETY.Item Performance of granular columns in dispersive soils(Thomas Telford Services Ltd ttjournals@ice.org.uk, 2014) Nayak, S.; Dheerendra Babu, M.R.; Shivashankar, R.; James, N.The soils found abundantly along the Konkan belt in peninsular India are lateritic soils and lithomargic clays. The locally available lithomargic clayey soils are problematic in the sense that their strength reduces drastically under saturation conditions, which is typical behaviour of the dispersive type of soil. Most foundations are placed on this soil layer. This paper presents results from a series of laboratory plate load tests carried out in unit cell tanks to investigate the behavior of granular columns in these weak (lithomargic clay) grounds. Tests are carried out with two types of loading: with the entire area in the unit cell tank loaded, to estimate the stiffness of the improved ground; and with only the granular column area loaded, to estimate its limiting axial capacity. Investigations were carried out by varying the area ratio (or spacing), diameter of granular columns, end condition and column configuration. The load-settlement behaviour, stiffness and bulging behaviour of granular columns are analyzed. It is found that the ground treated with granular columns exhibits a high load-carrying capacity and stiffness, and a significant reduction in settlement, compared with the untreated ground. © Ice publishing: All rights reserved.Item Some studies on engineering properties, problems, stabilization and ground improvement of lithomargic clays(Southeast Asian Geotechnical Society seags@ait.ac.th, 2015) Shivashankar, R.; Ravi Shankar, A.U.; Jayamohan, J.The study area for this paper is coastal Karnataka in India. The area has laterites and lateritic soils, and also a large number of sporadic lateritic hillocks. The soil stratification mainly consists of lithomargic clay sandwiched between the weathered laterite at top and the hard granitic gneiss underneath. Quite often the top laterites are removed in this area for use as bricks for construction purposes, thus exposing the underlying lithomargic clay. This coastal area receives copious amount of rainfall and a lot of developmental activities are taking place. These lithomargic clays, locally called as 'shedi soils' are also used as fill material in low lying areas, very often adjacent to water bodies. These soils behave as dispersive soils and are also highly erosive. A lot of engineering problems - such as foundation problems, subgrade problems, erosion and slope stability problems are being faced due to the presence of these shedi soils. Some laboratory studies on the engineering and strength properties of these lithomargic clays and stabilized soils, Ground Improvement on shedi grounds are made and reported.Item Influence of Granulated Blast Furnace Slag and Cement on the Strength Properties of Lithomargic Clay(Springer India sanjiv.goswami@springer.co.in, 2017) C. Sekhar, D.C.; Nayak, S.; Preetham, H.K.Utilizing industrial byproducts in soil stabilization benefits the economic, environmental and social benefits. Granulated blast furnace slag is a byproduct of iron and steel industry having oxides similar to that of cement but in different proportions. This study describes experimental results achieved by the use of granulated blast furnace slag (GBFS) and cement in stabilizing lithomargic clay for geotechnical applications. Soil was replaced by GBFS in percentages of 10, 15, 20, 25, 30, 35, 40, 45, 50% and cement of 2, 4, 6, and 8% by dry weight of soil is added. Various experimental studies like specific gravity, Atterberg limits, compaction, UCS, CBR and triaxial compression test, were performed on samples to understand the effect of these mixes on their few index and strength properties. The study also includes an investigation on a combination of optimum percentage of GBFS with varying percentage of cement and lime on their shear parameters. The study result shows significant improvement in the strength properties of the mixes. Hence it can be concluded that lithomargic clay stabilized with GBFS and cement/lime satisfy the strength requisite to be employed in the numerous geotechnical applications. © 2017, Indian Geotechnical Society.Item Utilization of granulated blast furnace slag and cement in the manufacture of compressed stabilized earth blocks(Elsevier Ltd, 2018) C. Sekhar, D.; Nayak, S.This study involves the investigation on utilization of granulated blast furnace slag (GBFS) and cement in the manufacture of compressed stabilized earth blocks (CSEB). Two locally available soils from Dakshina Kannada district, Karnataka, India were tested for their index and strength properties with replacement of granulated blast furnace slag (GBFS). An optimum percentage of replacement of GBFS was established and then varying percentages of cement was added for the production of compressed stabilized earth blocks (CSEBs). This stabilized soil was used for the manufacture of blocks of size 305 mm × 143 mm × 105 mm. All the blocks were cast to a target density, followed by the curing for 28 days. The blocks were subjected to compression test and water absorption test according to Indian Standard (IS) specifications. The test results showed that the CSEBs prepared with GBFS and cement can be utilized in masonry for load bearing wall construction. A small percentage of cement is sufficient for manufacturing the CSEBs when optimum GBFS content is replaced with that of soil, thereby reducing the energy consumption. © 2018 Elsevier LtdItem Effect of Column Configuration on the Performance of Encased Stone Columns with Basal Geogrid Installed in Lithomargic Clay(Springer, 2019) Nayak, S.; Vibhoosha, M.P.; Bhasi, A.Lithomargic clay is extensively found along the Konkan belt in peninsular India and serves as a foundation for most of the structures. The reduction in strength under saturated conditions makes this soil problematic causing a lot of engineering problems such as uneven settlements, erosion, slope failures, and foundation problems. This paper presents the effect of column configuration (i.e. equivalent number of columns with reduced diameter for the same surface area) on the performance of lithomargic clay reinforced with geogrid encased stone columns and basal geogrid layer. The investigations were performed both experimentally through small-scale models and through finite element analyses. The results were compared with the performance of lithomargic clay reinforced with ordinary and encased stone columns. A single geogrid encased stone column with a basal geogrid layer improved the load-carrying capacity of lithomargic clay by 180% while the percentage of increment in the case of a group of three geogrid encased stone column with basal geogrid layer having the same surface area was 210%. It was also observed that the geogrid encasement of stone columns reduced the maximum column bulging by 38%, whereas geogrid encased stone columns along with basal geogrid layer reduced the bulging by 82% compared to ordinary stone columns. © 2019, Springer Nature Switzerland AG.Item Erosion Studies on Lithomargic Clays(Springer, 2020) Thomas, B.C.; Shivashankar, R.; Jacob, S.; Varghese, M.S.Lithomargic clays are found at shallow depths in lateritic formations, sandwiched between hard lateritic crust at top and the parent granitic gneiss underneath. Many earlier studies have proved that the behaviour of these soils is similar to dispersive soils, and they are also found to be highly erosive. Very few and detailed studies on erosion of lithomargic clays are available in the literature. Lithomargic clays along the western coastal belt of peninsular India are available with varying percentages of sands and fines (especially silts, with negligible amount of clays occasionally). In this study, a number of hole erosion tests are conducted on controlled lithomargic clay samples with varying percentage of fines to study their erosion characteristics. The influence of degree of compaction, moulding water content, head causing flow, percentage silt content and plasticity index on the erosion rate index and critical shear stress of controlled lithomargic clay samples are being studied. The results of this study indicate that the critical shear stress for soils with higher silt fraction and fine sand content varied from 45 to 125 N/m2, whereas for soils with higher clay fraction and fine sand content the critical shear stress varied from 200 to 400 N/m2. The erosion rate increased with a decrease in percentage compaction in all the samples, and critical shear stress is found to be highest at optimum moisture content conditions. It is generally observed that soils with fines whose plasticity indices are high, are less erodible compared to soils with fines whose plasticity indices are low. © 2019, Indian Geotechnical Society.Item Laterites and lateritic soils: Geology, engineering properties and problems(International Association of Lowland Technology 1 Honjo Saga 840-8502, 2020) Shivashankar, R.; Thomas, B.C.Lateritic soils are abundantly available in the Konkan belt in the western coast of peninsular India, in the four southern states namely - Kerala, Karnataka, Goa and Maharashtra. Along with heavy rainfall (annual rainfall of 2000mm - 4000mm), the region is characterised by high humidity and little variation in temperatures. The typical stratification in lateritic areas consists of soft to hard lateritic crust at the top - about 3m thick, underlain by a layer of lithomargic clay (8 to 10m thick) underlain by parent rock, which is granitic gneiss. This paper briefly discusses the following aspects of lateritic soils (a) geotechnical properties, including those of laterites, lithomargic clays, lateritic lithomarges and lithomargic laterites (b) erosion studies from hole erosion tests (c) slope stability problems of excavated slopes in lateritic formations (d) role of vegetation i.e. turfing and/or trees on slopes in the stability of slopes. It is concluded that lateritic soils, especially lithomargic clays and lateritic lithomarges (1) behave somewhat like dispersive soils. (2) They are highly erosive by nature, especially lithomargic clays with higher content of sand and silt (3) Stability of both excavated and embankment slopes depends on good drainage control. Providing berms and vegetation on slopes adds to stability of slopes. © 2020 International Association of Lowland Technology. All rights reserved.