Conference Papers

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    Modeling of soil-structure interaction for reinforced breakwater foundation subjected to earthquake and tsunami loading
    (CRC Press/Balkema, 2019) Hazarika, H.; Chaudhary, B.; Nozu, A.; Kohama, E.; Suzuki, K.; Murakami, A.; Fujisawa, K.
    This paper describes the soil-structure interaction behavior of a new reinforcing technique for breakwater foundation against earthquake and tsunami induced damage. The technique involves the use of gabion on the top of rubble mound, reinforcing the foundation soil with steel sheet piles, and the use of sealing material between the sheet piles and breakwater. The effectiveness of the proposed technique and the soil structure interaction during earthquake and tsunami loading were evaluated through physical and numerical modeling. As part of the physical modeling for such soil-structure interaction problem, a series of 1g shaking table tests and centrifuge model tests were performed. In addition, a hydraulic model testing apparatus was developed, which can simulate the soil-structure interaction during tsunami overflow, the resulting seepage as well as the scouring. Numerical simulation was also performed for evaluating the effect of tsunami overflow. Soil-structure interaction behaviors were made clear through comparisons of conventional foundation and reinforced foundation models. © 2019 Associazione Geotecnica Italiana, Rome, Italy.
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    Physical Model Tests for Newly Developed Breakwater Foundation Subjected to Earthquake and Tsunami
    (Springer Science and Business Media Deutschland GmbH, 2021) Chaudhary, B.; Hazarika, H.; Murakami, A.; Fujisawa, K.
    Many breakwaters damaged due to earthquake and tsunami in the past. For example, several breakwaters collapsed by the 2011 off the Pacific Coast of Tohoku Earthquake and subsequent tsunami. It was found that these breakwaters damaged mainly due to the failure of their foundations. Therefore, countermeasures are urgently needed to be developed for breakwater foundation in order to make the breakwater safe against earthquake and tsunami. Recently, new countermeasures were developed by the authors for breakwater foundation in order to make it resilient against an earthquake and tsunami. This paper deals with evaluation of effectiveness of the developed foundation model by conducting shaking table tests and tsunami overflow tests. As reinforcing countermeasures, steel sheet piles and gabions are provided in the breakwater foundation. To see the performance of the developed model, comparisons are made between the developed foundation model and conventional foundation. Through the tests, it was found that the reinforced foundation performed well in reducing damage of the breakwater caused by the earthquake and tsunami. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
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    Stability of Reinforced Soil Quay Wall Subjected to Combined Action of Earthquake and Tsunami
    (Springer Science and Business Media Deutschland GmbH, 2021) Sajan, M.K.; Chaudhary, B.
    Reinforced soil quay walls are used as shore protection systems. Generally, horizontal layers of geogrids are provided as reinforcement in the backfill soil of the quay wall. These structures are internally stabilized by mobilized tensile strength of reinforcements. A quay wall can be subjected to tsunami load and earthquake load simultaneously. This condition occurs when an earthquake aftershock reaches the quay wall structure at the same time of a tsunami impact. Therefore, a combined analysis of quay walls subjected to earthquake and tsunami at the same time is necessary. In this study, horizontal slice method is used to evaluate the stability of the reinforced soil quay wall subjected to earthquake and tsunami. The failure surface is generated by optimizing the angle of failure plane of each slice, so that the mobilized tensile force on the reinforcement is maximum. Thus, the generated failure surface could justify the actual failure surface. It was observed that normalized force acting on the reinforcement is considerably increased under the combined effect of earthquake and tsunami. Stability of the wall is evaluated by varying several parameters, such as acceleration coefficient of earthquake motion, internal friction angle of soil, inclination and height of the quay wall, height of seawater level and height of tsunami waves, to find out the effect of these parameters on normalized reinforcement strength. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
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    Swell-Compressibility Behavior of Geopolymer Blended Expansive Clays
    (Springer Science and Business Media Deutschland GmbH, 2021) Thotakura, V.; Sunil, B.M.; Chaudhary, B.
    This paper presents the influence of GGBS-based geopolymer on swell-compressibility characteristics of oven-dry, expansive clay passing 4.75 mm sieve. One-dimensional swell-consolidation tests were conducted on the expansive clay passing through 4.75 mm sieve to which GGBS was added at 0, 5, 10, 15, and 20% by dry weight of the clay. Rate of heave, swell potential, swelling pressure, and linear shrinkage were evaluated. Rate of heave and swell potential decreased significantly with increase in GGBS content. The paper also explores the microstructure behavior and surface texture of the GGBS-based geopolymer–clay blends using the scanning electron microscopy (SEM). The SEM results revealed that the higher Si/Al compounds increase the dense phase of geopolymer products. Moreover, geopolymer synthesis can contribute to the bulk utilization of industrial by-products. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
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    Assessment of Seismic Liquefaction of Soils Using Swarm-Assisted Optimization Algorithm
    (Springer Science and Business Media Deutschland GmbH, 2021) Thotakura, V.; Durga Prasad, C.D.; Chaudhary, B.; Sunil, B.M.
    Assessment of liquefaction potential of soils due to the earthquake has been carried out in this research using the nature-inspired Metaheuristic swarm-assisted algorithm (PSO). An assessment has been made on the basis of actual field data from the previous research. The field data consists of 59 sets having variables of total stress of soil (⌠o), effective stress of the soil (⌠′o), percentage fines, mean size of soil particles (D50), standard penetration value (SPT), the equivalent dynamic shear stress (Tav/⌠′o), maximum horizontal acceleration at ground surface (a/g) and the earthquake magnitude (M). PSO-based models were developed for both single variable and multivariable linear approaches. The results revealed that for the assessment of liquefaction of soils, the developed PSO models perform good estimations in terms of the errors and convergent solution. And also, with a damping coefficient and varying input variables, there is a significant improvement in the best solution. These developed models can be useful for practicing engineers in the field. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
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    Tsunami Resilient Foundation for Breakwater: Centrifuge Model Tests
    (Springer Science and Business Media Deutschland GmbH, 2021) Chaudhary, B.; Hazarika, H.; Murakami, A.; Fujisawa, K.
    Many coastal protection structures collapsed due to the past earthquakes and tsunamis. For example, several breakwaters damaged during the 2011 Great East Japan Earthquake and Tsunami in Japan. Due to the failure of the breakwaters, the tsunami waves could not be blocked by the breakwaters. Thus, the tsunami entered in the coastal areas; and imposed deep devastation there. It was found that the breakwaters damaged mainly due to their foundation failures. In order to mitigate such damage of breakwater caused by earthquake and tsunami, new techniques were developed by the authors for breakwater foundation. In the technique, gabions and sheet piles are used in breakwater foundation. Effectiveness of the developed foundations model of breakwater were evaluated by conducting centrifuge model tests. It was observed that the developed models could mitigate damage, and make the breakwater resilient against earthquake and tsunami-induced damage. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
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    Review of Literature on Design of Rubble Mound Breakwaters
    (Springer Science and Business Media Deutschland GmbH, 2023) Akarsh, P.K.; Chaudhary, B.
    Breakwaters are offshore structures constructed to protect the coastal and port structures from uncertain and extreme wave conditions. It creates tranquility in and around the harbor side for smooth transactions of ships. Depending upon the availability of rocks, depth of water, geotechnical nature of the sea bed, and its functional requirement, breakwaters are classified as rubble mound breakwaters, caisson type, and composite breakwaters. Rubble mound is a flexible, heterogeneous, trapezoidal structure consisting of quarried rocks in the core and artificial armor as a protection cover. Armor units at the outer layer absorb most of the energy and under-layers prevent transmission of the wave energy. The main advantage of the rubble mound is its failure is not immediate and can be repaired by adding the stones in the flushed-out part. More than 50% of breakwaters constructed around the world are of rubble mounds. Looking at its importance for coastal structures, this paper gives an overview of the basic aspects of rubble mound breakwaters, design considerations, and its failure conditions. The design of rubble mound breakwaters include hydraulic stability of it against wave actions, structural components design, and geotechnical considerations. The common modes of rubble mound failure are hydraulic damage, erosion of subsoil, slope failures, toe erosion, overtopping, liquefaction of subsoil, crest erosion, and leeside damage. The failure of rubble mound breakwater at Ergil fishery port, Turkey due to Kocaeli earthquake of 1999 has been explained to support this part. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
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    A Study on Aquaculture Waste Leachate Transport Through Soil
    (Springer Science and Business Media Deutschland GmbH, 2023) Thotakura, T.V.; Sunil, B.M.; Chaudhary, B.
    Aquaculture waste is one of the emerging wastes due to rapid expansion and intensification of aquaculture practices and less attention has been paid for environmental concern as compared with municipal waste. Moreover, in the delta region of Andhra Pradesh, nearly one-third of the land cover is occupied by the aquaculture ponds. Major contaminants in aquaculture ponds are rich in nutrients, chemicals, disinfectants, feed residues, metals, minerals, and nitrates. This paper presents the aquaculture waste leachate and clay interaction. Our findings revealed that ammonia interaction with the clay particles significantly influence the hydraulic behavior of the clays. Further, long-term clay-leachate interactions lead to negative environmental consequences. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
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    Understanding the Role of Biological Oxygen Demand in Aquaculture Waters in the Western Delta Region of Andhra Pradesh
    (Springer Science and Business Media Deutschland GmbH, 2023) Thotakura, T.V.; Sunil, B.M.; Chaudhary, B.
    The aquaculture industry with intensive farming activities has been gaining potential benefits to the nation’s economic growth and food security. However, due to intensive farming, harmful pollutants are emerging with a higher concentration of biological oxygen demand (BOD), chemical oxygen demand (COD), and ammonia nitrates are more concerns. This study presents the role and assessment of BOD for the aquaculture ponds in the western delta region of Andhra Pradesh. The collected water samples at various locations in the study area have been tested for physicochemical characteristics and the test data used for BOD prediction. For evaluating the sensitivity of the prediction model, particle swarm optimization (PSO) with variations of inertia weight and damping factors is used to obtain the best global solution. As a result, prediction models developed for assessing BOD using PSO show convergent predictions. So, based on the prediction results, the implementation of prediction models of BOD using PSO could be helpful for sustainable aquaculture management in the western delta region of Andhra Pradesh. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
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    Influence of Aquaculture Sludge on Volume Change Behavior of Expansive Clays
    (Springer Science and Business Media Deutschland GmbH, 2023) Thotakura, T.V.; Sunil, B.M.; Chaudhary, B.
    Aquaculture waste sludge (AWS) from the aquaculture ponds in the delta region of Andhra Pradesh is most popular. Intensive aquaculture practice involves usage of higher dosages of minerals and chemicals in the aquaculture ponds. Further, due to the intensive activity, there is a formation of AWS at the bottom of the ponds. In this study, experimental investigation was carried with various concentrations of ASW sludge was blended with the expansive clays. A summary of one-dimensional swell-consolidation studies on expansive clays blended with AWS is presented. Rate of heave, swell potential, and swelling pressure significantly decreased with the increase in ASW content. The paper also explores microstructural behavior of the expansive clays blended with AWS. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.