Conference Papers
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Item 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.Item 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.Item Seepage Analysis of Resilient Rubble Mound Breakwater Under Tsunami Overflow: Numerical Analysis(Springer Science and Business Media Deutschland GmbH, 2023) Sajan, M.K.; Chaudhary, B.A breakwater is an offshore structure which is constructed to protect ports and harbours from the destructive effects of sea waves, currents, typhoons, and even tsunamis by reflecting and dissipating their wave energies. Among the various types of breakwaters, the rubble mound (RM) breakwater is the most common type constructed near the seacoasts of many countries across the globe. The most devastating natural hazard that a breakwater could possibly encounter during its design life is a tsunami wave. Several breakwaters were severely damaged or completely collapsed in several countries during past tsunamis. The coastal areas of India bore the brunt of the damage during the 2004 Indian Ocean tsunami. Therefore, it is utmost important to develop new techniques such as placing special gabions and rows of sheet piles as countermeasures for making RM breakwaters tsunami resilient. One of the longest breakwaters in India, the north breakwater at the Ennore Port (Chennai) has been chosen as prototype. The numerical modelling of the RM breakwater along with the seabed soil with two layers has been done in Plaxis 2D to observe the effectiveness of these countermeasures during tsunami-induced seepage through the breakwater and seabed soils. It was found that the provision of special gabions with impermeable layer and sheet piles beneath the mound can effectively prevent the seepage of water that occurs during tsunami overflow. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item Stability Analysis of Rubble Mound Breakwaters Under Tsunami Overflow(Springer Science and Business Media Deutschland GmbH, 2024) Sajan, M.K.; Chaudhary, B.; Akarsh, P.K.; Kumar, S.Rubble mound (RM) breakwaters are the most commonly constructed breakwaters across the globe. Even though the breakwaters are designed to withstand to dynamic wave loadings, a natural disaster such as tsunami could impart additional loadings beyond the designed limits and thereby reduce the stability of the structure. Unfortunately, several RM breakwaters were severely damaged or even collapsed under the impact of past tsunamis such as the 2004 Indian Ocean tsunami and 2011 Great East Japan tsunami. The failure of these breakwaters would lead to the inundation of tsunami waves to the coastal areas causing devastating damages to life and property. Therefore, it is relevant to make the RM breakwaters resilient against tsunami impacts, so that the breakwater can either completely prevent or at least reduce the impact height of tsunami waves. In order to design a RM breakwater resilient against tsunami, the failure mechanisms under tsunami overflow conditions have to be properly understood. The present study thus aims to numerically evaluate the stability of RM breakwaters under tsunami overflow conditions. The cross-section details of the North breakwater at the Ennore Port, Chennai, India have been modelled at full scale in the finite element software Plaxis. The model was then subjected to a tsunami overflow condition. The corresponding deformations and stability of the RM breakwater were estimated. It was observed that the stability of the breakwater was considerably reduced under tsunami overflow conditions. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.Item Numerical Analysis on Geogrid-Reinforced Coastal Structures Under Tsunami(Springer Science and Business Media Deutschland GmbH, 2025) Sajan, M.K.; Chaudhary, B.; Akarsh, P.K.; Sah, B.Coastal structures such as breakwaters play a crucial role in coastal protection, shielding communities from the relentless forces of waves and storms. However, historical tsunami events have exposed vulnerabilities in these breakwaters, leading to instances of collapse and extensive damage. The collapse of rubble mound breakwaters during the past 2004 Indian Ocean and 2011 Great East Japan tsunamis highlights the urgent need for effective countermeasures to improve their tsunami resilience. In response, this research investigates the tsunami behavior of these coastal structures. It examines potential reinforcement technique of adopting geogrids on the breakwater slopes to mitigate tsunami-induced damage. Through advanced numerical analysis using finite element modeling, geogrid reinforcements are introduced on either side of the breakwater to assess their effectiveness in reducing tsunami-induced settlements, horizontal displacements, and stability. The incorporation of geogrids emerges as a promising solution, offering several advantages over conventional breakwater models. Results demonstrate that geogrid effectively reduces the settlement of reinforced breakwater by up to 81% under a tsunami. Moreover, geogrids demonstrate superior performance in mitigating lateral displacements and stability, highlighting their potential to enhance the tsunami resilience of the breakwater. A parametric study was performed on the influence of the tensile strength of geogrids in improving the stability of the reinforced breakwater. This study contributes valuable insights to the field of coastal engineering and disaster resilience by providing a comprehensive analysis of geogrid reinforcements in mitigating tsunami-induced damage to rubble mound breakwaters. The findings underscore the importance of proactive measures in protecting coastal communities against the escalating threat of tsunamis, emphasizing the role of innovative engineering solutions in building resilient coastal infrastructure. © Deep Foundations Institute 2025.