D. N. Arnepalli

Bio: D. N. Arnepalli is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topic(s): Geosynthetic clay liner & Lime. The author has an hindex of 10, co-authored 35 publication(s) receiving 348 citation(s). Previous affiliations of D. N. Arnepalli include Indian Institute of Technology Bombay & Indian Institutes of Technology.

Comparison of Methods for Determining Specific-surface Area of Fine-grained Soils

Abstract: Characteristics of fine-grained soils primarily depend on their specific-surface area and hence, reliable determination of this parameter is essential. In this context, researchers have employed quite sophisticated instruments (viz., a BET surface area analyzer, the mercury intrusion porosimetry, internal reflectance spectroscopy, X-Ray diffraction and gas pycnometer etc.) and methodologies (viz., sorption of Methylene Blue dye, Ethylene Glycol Monoethyl Ether and p-Nitrophenol) to determine specific-surface area of these soils. However, most of these methodologies are found to be quite tedious, cost and time intensive. Apart from this, the results obtained are contentious due to the inherent limitations associated with either the instruments employed or the basic assumptions made for computing the specific-surface area of the soil. Hence, it becomes mandatory to evaluate the efficiency of these methodologies for determining specific-surface area of fine-grained soils. With this in view, different types of soils were considered in this study and their specific-surface area was determined, by following different methodologies, and the results were evaluated critically. In addition, attempts were made to develop relationships between the basic properties of fine-grained soils (viz., liquid limit, cation-exchange capacity, activity, and free swell index) and the specific-surface area. These relationships will be of immense help to the practicing engineers and research fraternity.

Antioxidant Depletion from a High Density Polyethylene Geomembrane under Simulated Landfill Conditions

Abstract: Accelerated aging tests to evaluate the depletion of antioxidants from a high density polyethylene geomembrane are described. The effects of temperature, high pressure, and continuous leachate circulation on the aging of geomembranes in composite liner systems are examined. The antioxidant depletion rates (0.05, 0.19, and 0.41 month−1 at 55, 70, and 85°C , respectively) obtained for the simulated landfill liner at 250 kPa vertical pressure are consistently lower than that obtained from traditional leachate immersion tests on the same geomembrane (0.12, 0.39, and 1.1 month−1 at 55, 70, and 85°C ). This difference leads to a substantial increase in antioxidant depletion times at a typical landfill liner temperature ( 35°C ) with 40 years predicted based on the data from the landfill liner simulators tests, compared to 15 years predicted for the same geomembrane based on leachate immersion tests. In these tests, the crystallinity and tensile yield strain of the geomembrane increased in the early stages of ...

A Critical Appraisal of the Role of Clay Mineralogy in Lime Stabilization

Abstract: The stabilization of problematic fine-grained soils using lime as an admixture is a widely accepted practice, owing to its simplicity and cost-effectiveness. The optimal quantity of lime required for soil stabilization primarily depends upon the reactive nature of soil as well as the degree of improvement desired. The term ‘optimum lime content’ (OLC) defines the amount of lime required for satisfying the immediate/short-term soil–lime interaction, and still providing sufficient amount of free calcium and high residual pH necessary to initiate long-term pozzolanic reaction. Previous researchers proposed various empirical correlations and experimental methodologies for determining OLC, in terms of clay-size fraction and plasticity characteristics of virgin soil. However, the limiting lime content obtained using various conventional methods does not account for the most influencing inherent clay mineralogy of the soil; and hence, the results of these methodologies are observed to be quite disagreeing with each other. In view of these discrepancies, the present study attempts to validate the existing conventional methodologies for OLC determination at an elementary level, by comprehending the fundamental chemistry following soil–lime interactions. Based on the theoretical and experimental observations, it is quite evident that the accuracy of conventional tests is limited by combined influence of chemical and mineralogical properties of soils. Hence, it is proposed to develop a precise methodology to ascertain the required optimal lime dosage based on scientific criteria, by incorporating the influence of soil properties such as clay mineralogy, specific surface area, soil pH, cation exchange capacity, soil acidity, base saturation capacity, and buffer capacity.

Insight into hydraulic conductivity testing of geosynthetic clay liners (GCLs) exhumed after 5 and 7 years in a cover

Abstract: Four geosynthetic clay liners (GCLs) serving as single liners were exhumed from below 0.7 m of silty sand on a 3:1 (horizontal:vertical) north-facing slope at the QUELTS site in Godfrey, Ontario, a...

Thermal exposure conditions for a composite liner with a black geomembrane exposed to solar radiation

Abstract: A black 1.5 mm geomembrane (GMB) and geosynthetic clay liner (GCL) liner were placed on both a 3H: 1V (18.4°) slope and a gently sloping (3%) base (latitude 44°34′15″N) and left exposed for 4.7 years. The observed solar radiation, ambient air temperature, temperature at the interface between the GMB and GCL, and temperature at various depths (to 600 mm) in the underlying silty sand soil are reported. The interface temperature was up to 40°C higher than ambient temperature on a sunny day. The difference between interface temperature on the slope and base was minimal near summer solstice and increased significantly earlier and later in the year (except when covered in snow). There was significant variability in GMB and interface temperature depending on the contact conditions between the GMB and GCL. The interface temperatures at wrinkles could be 15°C higher than other locations where there was intimate contact between GMB and GCL. Snow-cover insulated the liner from solar radiation and extreme t...

Handbook of Chemistry and Physics

Abstract: There is a special reason for reviewing this book at this time: it is the 50th edition of a compendium that is known and used frequently in most chemical and physical laboratories in many parts of the world. Surely, a publication that has been published for 56 years, withstanding the vagaries of science in this century, must have had something to offer. There is another reason: while the book is a standard fixture in most chemical and physical laboratories, including those in medical centers, it is not as frequently seen in the laboratories of physician's offices (those either in solo or group practice). I believe that the Handbook can be useful in those laboratories. One of the reasons, among others, is that the various basic items of information it offers may be helpful in new tests, either physical or chemical, which are continuously being published. The basic information may relate

Microbial and Plant-Assisted Bioremediation of Heavy Metal Polluted Environments: A Review

Abstract: Environmental pollution from hazardous waste materials, organic pollutants and heavy metals, has adversely affected the natural ecosystem to the detriment of man. These pollutants arise from anthropogenic sources as well as natural disasters such as hurricanes and volcanic eruptions. Toxic metals could accumulate in agricultural soils and get into the food chain, thereby becoming a major threat to food security. Conventional and physical methods are expensive and not effective in areas with low metal toxicity. Bioremediation is therefore an eco-friendly and efficient method of reclaiming environments contaminated with heavy metals by making use of the inherent biological mechanisms of microorganisms and plants to eradicate hazardous contaminants. This review discusses the toxic effects of heavy metal pollution and the mechanisms used by microbes and plants for environmental remediation. It also emphasized the importance of modern biotechnological techniques and approaches in improving the ability of microbial enzymes to effectively degrade heavy metals at a faster rate, highlighting recent advances in microbial bioremediation and phytoremediation for the removal of heavy metals from the environment as well as future prospects and limitations. However, strict adherence to biosafety regulations must be followed in the use of biotechnological methods to ensure safety of the environment.

Predicting the saturated hydraulic conductivity of soils: a review

Abstract: This paper examines and assesses predictive methods for the saturated hydraulic conductivity of soils. The soil definition is that of engineering. It is not that of soil science and agriculture, which corresponds to “top soil” in engineering. Most predictive methods were calibrated using laboratory permeability tests performed on either disturbed or intact specimens for which the test conditions were either measured or supposed to be known. The quality of predictive equations depends highly on the test quality. Without examining all the quality issues, the paper explains the 14 most important mistakes for tests in rigid-wall or flexible-wall permeameters. Then, it briefly presents 45 predictive methods, and in detail, those with some potential, such as the Kozeny-Carman equation. Afterwards, the data of hundreds of excellent quality tests, with none of the 14 mistakes, are used to assess the predictive methods with a potential. The relative performance of those methods is evaluated and presented in graphs. Three methods are found to work fairly well for non-plastic soils, two for plastic soils without fissures, and one for compacted plastic soils used for liners and covers. The paper discusses the effects of temperature and intrinsic anisotropy within the specimen, but not larger scale anisotropy within aquifers and aquitards.

Short- and long-term leakage through composite liners. The 7th Arthur Casagrande Lecture1 1This lecture was presented at the 14th Pan-American Conference on Soil Mechanics and Geotechnical Engineering, Toronto, Ont., October 2011, and a pre-print appeared in the conference proceedings.

Abstract: The factors that may affect short-term leakage through composite liners are examined. It is shown that the leakage through composite liners is only a very small fraction of that expected for either...