Faculty Publications

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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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    Investigations on Stone Matrix Asphalt Mixes by Utilizing Slag and Cellulose Fiber
    (Springer Science and Business Media Deutschland GmbH, 2023) Marathe, S.; Akarsh, P.K.; Bhat, A.K.; Mahesh Kumar, M.
    Stone Matrix Asphalt (SMA) has become one of the most admired Asphalt Pavement layers due to its superior deformation-resistant capacity through a coarse stone skeleton providing more stone-on-stone contact than the other Dense Graded Asphalt (DGA) mixes. SMA has proved superior on heavily trafficked roads and in industrial applications. SMA has distinct advantages as a Surfacing, due to its potential for high resistance to fatigue and rutting. In the present study, the SMA specimens were prepared by incorporating Ground Granulated Blast Furnace Slag (GGBS) as filler and the Marshall properties were studied. Further, for the optimum Marshall mix (containing 2.5% of GGBS), the cellulose fiber was added. The results have shown that the maximum strength was obtained for the SMA mix containing 7% of bitumen content with 2.5% of GGBFS and 0.3% of cellulose fiber. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
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    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.
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    Seismic Responses of Rubble Mound Breakwater: Numerical Analyses
    (Springer Science and Business Media Deutschland GmbH, 2024) Akarsh, P.K.; Chaudhary, B.; Sajan, M.K.; Kumar, S.
    Rubble mound breakwater is a coastal structure, which is constructed to provide tranquil conditions in and around the port areas. Generally, the rubble mound structures are subjected to vigilant waves throughout the year. After the earthquakes of Kobe (1995), Kocaeli (1999), Tohoku (2011) etc. it is observed that the breakwaters can collapse due to failure of foundation and by seismic activity. Hence, in order to assess this problem, the current investigation deals with the study of rubble mound breakwaters and it is behavior against the seismic forces using numerical analysis. A finite element software PLAXIS is used for the numerical simulations. For study, a prototype has been selected and numerical model developed is a conventional rubble mound breakwater. In countermeasure model, the sheet piles in the foundation soil on extreme side of mound were considered. The numerical analyses have been done for constant seismic loading and soil properties. The parameters like vertical settlement and horizontal displacement were determined at different nodes. The vertical settlement was observed to be predominant in the crest region and it was reduced by 38% in countermeasure model. The displacement contours were significantly seen in core and armor units. The horizontal displacement of mound was seen by lateral movement of outer layers and it was 23% lesser for sheet pile reinforced model. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.
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    Response of Offshore Wind Turbine Foundation Subjected to Earthquakes, Sea Waves and Wind Waves: Numerical Simulations
    (Springer Science and Business Media Deutschland GmbH, 2024) Kumar, S.; Chaudhary, B.; Sajan, M.K.; Akarsh, P.K.
    Offshore wind turbines are an economical and sustainable method for generating renewable energy over extended periods. They efficiently harness wind power and are strategically located far from residential areas in the sea, resulting in minimal noise pollution. These towering structures rely on wind as their primary energy source and are installed at varying water heights from shallow to medium depths. The critical aspect of ensuring the stability of the foundation for such massive and tall structures becomes particularly important, especially in regions prone to earthquakes. This research paper focuses into the influence of wind loading on offshore wind turbine platforms, with specific emphasis on the suction caisson foundation. To assess the effects of wind loads, numerical analyses were performed using the finite element software PLAXIS. The findings reveal that horizontal deflection and shear stress increase as the angle of internal friction and unit weight decrease. Additionally, the study conducts parametric analyses to explore the impact of other variables on the behaviour of the turbine. These conclusions emphasize the significance of designing resilient foundations for offshore wind turbines, considering factors such as wind loads, soil characteristics, and structural parameters. This ensures their long-term stability and effectiveness as a sustainable source of energy. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.
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    Mitigation Technique Against Earthquake-Induced Damages by Using Scrap Tire Chips in Shallow Foundations
    (Springer Science and Business Media Deutschland GmbH, 2025) Akarsh, P.K.; Shivasharan, S.; Ujwal, B.; Udaykiran, L.V.; Chaudhary, B.
    In recent years, earthquakes like the 2016 Kumamoto earthquake, the 2018 Sulawesi earthquake, and the 2023 Turkey-Syria earthquake have seriously damaged buildings and their foundations. This paper investigates the effectiveness of utilizing scrap tire chips beneath shallow foundations to mitigate earthquake-induced building damage. Shake table tests were conducted on physical models, including conventional foundations and foundations augmented with scrap tire layers. The objective was to assess the seismic performance and compare their behavior under sinusoidal input motion. The results of shake table tests demonstrated that incorporating a scrap tire chip layer beneath foundations significantly improves their ability to withstand seismic forces. The settlement of footing in the countermeasure model was reduced by 65.6% compared to the conventional one. The acceleration amplitude recorded at the top of the footing was decreased by 68.8% in the countermeasure model. Thus, the presence of the scrap tire layer effectively dissipates and redistributes seismic energy, thereby reducing the transmission of damaging forces to the superstructure. The enhanced damping characteristics and increased flexibility offered by the scrap tire layer contribute to improved seismic performance. The findings of this study highlight the potential benefits of using scrap tire chips as a cost-effective material for mitigating earthquake-induced damages on foundation structures. Using scrap tire chips not only offers a sustainable alternative for waste management but also provides an efficient approach to enhancing buildings’ seismic resilience. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.
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    Dynamic Analysis on the Seismic Resilience of Rubble Mound Breakwaters
    (Springer Science and Business Media Deutschland GmbH, 2025) Sajan, M.K.; Chaudhary, B.; Akarsh, P.K.; Sah, B.
    In the aftermath of past earthquakes causing damage to rubble mound (RM) and exposing coastal infrastructure to potential tsunami waves, this paper presents an in-depth investigation into the seismic performance of these critical coastal defenses. Employing advanced finite element analysis software, the study utilizes sinusoidal input ground motions with varying accelerations to simulate the seismic response of RM breakwaters. The research methodology entails meticulous finite element modeling of conventional breakwaters and the strategic integration of reinforcements, such as sheet piles and geogrids. A detailed analysis of displacement profiles and changes in pore pressures within the seabed soil beneath the RM breakwater is conducted, offering crucial insights into its seismic behavior. The investigation explores diverse combinations of reinforcements to assess their efficacy in fortifying the breakwater against seismic loading. Seismic response is simulated by imposing sinusoidal input waves as displacements at the bottom boundary of the soil layer, with free-field boundaries at either end to eliminate reflective effects. This research significantly contributes to the optimization of RM breakwater designs, providing practical strategies for enhancing their seismic performance in coastal engineering applications. The use of finite element analysis facilitates a nuanced understanding of dynamic interactions, allowing for the development of robust and resilient coastal structures to withstand seismic challenges and mitigate potential damages to coastal infrastructure and life. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.
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    Behavior of Offshore Wind Turbine Foundation Under Seismic Loading: Numerical Simulations
    (Springer Science and Business Media Deutschland GmbH, 2025) Kumar, S.; Chaudhary, B.; Sajan, M.K.; Akarsh, P.K.; Sah, B.
    Offshore wind energy has emerged as a pivotal source of renewable energy, driven by the need to address climate change and reduce reliance on fossil fuels. The behavior of offshore wind turbine foundations plays a critical role in ensuring the efficiency and durability of these structures in harsh marine environments. The numerical simulations of an offshore wind turbine foundation under seismic loading are presented in this paper, with an emphasis on vertical settlement and horizontal displacement. The dynamic behavior of the foundation is evaluated under different soil properties and caisson geometry using sophisticated finite element modeling. The parametric study shows that increasing the length of suction caisson foundation there is an appreciable amount of reduction in vertical settlement of foundation due deeper embedment of caisson. A deeper embedment provides increased resistance to horizontal displacement because the foundation interacts with more stable soil layers. Because denser sand has a higher unit weight, it resists compression better, which reduces overall soil compression under load and minimizes vertical settling of foundations. Sand unit weight influences an offshore wind turbine caisson foundation’s horizontal displacement by boosting seabed interaction, increasing vertical stress, and possibly offering more resistance because of its higher shear strength. The results highlight the need for strict seismic design standards to guarantee the dependability and security of offshore wind farm foundations in seismically active areas, the paper ultimately contributes to the development of more efficient, sustainable, and resilient offshore wind energy infrastructure. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.
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    Numerical Simulations for Response of Offshore Wind Turbine Monopile Under the Action of Dynamic Loading
    (Springer Science and Business Media Deutschland GmbH, 2025) Barik, T.; Chaudhary, B.; Sah, B.; Kumar, S.; Akarsh, P.K.
    Wind energy is one of the most important renewable energy sources; and specifically offshore wind turbines (OWTs) are more convenient ones because of the presence of uninterrupted high-velocity winds in the offshore area. To stabilize the OWT structure, the foundation plays the most significant role. Most of the offshore wind farms employ fixed type foundations for shallow water depth. Among the fixed type foundations, monopiles arose as the first choice for the scientists and practicing engineering because of its ease of installation and economical aspects. Besides, due to high magnitude of wind pressure and wave force in offshore areas, these OWTs face a heavy dynamic lateral loading which creates unbalanced forces and moments as well as vibrations which can make the whole structure unstable by affecting these monopiles. Research has been done in the past on monopoles, but still the responses could not be understood completely. Therefore, an attempt has been made in this study to investigate the lateral behavior of monopile-tower structure under the action of dynamic lateral loadings using Finite Element (FE) analyses. A 3D numerical model has been developed in ABAQUS program; and the numerical model has been validated with the available literature. In addition, parametric studies were conducted to understand the effects of loading conditions, pile geometric configuration, and soil shear parameters on the lateral response of the monopile-tower assembly. Results obtained from the rigorous numerical analyses demonstrate that the wind load in isolation can significantly augment the lateral displacement of OWT hubs. Moreover, an additional wave load may diminish this displacement at the hub. Additionally, the length and diameter of the monopile also exert a notable influence on governing the lateral response. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.
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    Effects of High Cyclic Strains on Dynamic Properties of Cohesionless Soils
    (Springer Science and Business Media Deutschland GmbH, 2025) Akarsh, P.K.; Chaudhary, B.; Sajan, M.K.; Chikkanna, T.; Talkad, P.
    Soils can experience large cyclic shear strains (>1%) under dynamic loading circumstances such as earthquakes. Determining dynamic properties such as damping ratios and shear modulus is crucial in the design of earthquake-resistant structures. From past studies, it was understood that the dynamic behaviour of soils at higher strains (>0.01%) is different from soils subjected to lower strains (<0.001%) because of nonlinear stress–strain behaviour and damping characteristics at higher strains. Furthermore, it was evident that the majority of tests were carried out on lower strains and only few numbers of studies were reported on tests for higher strains. Hence in this study, the dynamic properties for locally available cohesionless soils tested under high cyclic strains are presented. Generally, the dynamic properties were determined up to strain levels <1% considering a symmetrical hysteresis loop. But the loop becomes asymmetric as the strain level increases and due to which, dynamic properties are over-estimated. So, in this study, the dynamic properties of saturated sand were determined by an actual asymmetric hysteresis loop. Strain-controlled cyclic triaxial tests were conducted on reconstituted soil specimens at a low frequency (0.25 Hz) for variable peak strain levels (0.15–1.5%). The specimens were prepared at different relative densities (30–90%) and consolidated at an effective confining pressure of 100 kPa. The findings of the study revealed that the soil’s shear modulus would degrade more quickly or that the modulus reduction ratio would reduce at higher strain levels (γ ≥ 1%) due to an increase in pore water pressure during undrained cyclic loading. It also turns out that at higher strain values (>1%), the damping ratio significantly decreased. Hence, it is not obvious to extrapolate the trend seen for γ < 1% to get the results for γ > 1%. This work would be helpful for geotechnical practicians and researchers to have insights into the existing methodology for finding the dynamic properties of cohesionless soils at higher cyclic strains. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.