Faculty Publications

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Comprehensive Analysis of Gabion Configurations for Modelling Tsunami-Resilient Rubble Mound Breakwaters
(Springer, 2025) Sajan, M.K.; Sah, B.; Kumar, S.; Chaudhary, B.
Coastal communities face significant threats from tsunamis, which cause extensive damage to infrastructure and endanger human lives. Rubble mound breakwaters, widely adopted structures in ports and harbours globally, serve as the first line of defense against tsunami waves. However, their failures in past tsunamis highlight the need for enhanced resilience. The performance of rubble mound breakwaters under tsunami conditions has received limited research attention, and few studies have explored effective countermeasures to mitigate tsunami-induced damages. This study addresses this research gap by performing a comprehensive evaluation through physical model tests, analytical studies and numerical simulations, focusing on the behaviour of rubble mound breakwaters under tsunami overflow. Observations from the responses of conventional models during overflow tests informed the proposal of a reinforcing technique utilizing gabions as a countermeasure to enhance tsunami resilience. Measurements of crest displacements and excess pore water pressure developed in both the foundation soils and the breakwater during tsunami overflow were ascertained to comparatively analyse the performance of the proposed reinforced models. An in-depth analysis was conducted on the placement and positioning of gabions to identify the most effective configuration for transforming a conventional rubble mound breakwater into a tsunami-resilient structure. Among the various gabion placement configurations studied, the stepped configuration demonstrated a remarkable 97.8% reduction in settlement during tsunami overflow. Further analytical and numerical studies were performed to assess the performance of the proposed gabion-reinforced model under tsunami overflow conditions. This proposed technique presents significant potential for protecting a wide range of coastlines by enhancing the resilience of rubble mound breakwaters against tsunamis. © The Author(s), under exclusive licence to Indian Geotechnical Society 2025.
Developing Tsunami-Resilient Rubble Mound Breakwater: Novel Gabion-Based Technique
(American Society of Civil Engineers (ASCE), 2025) Sajan, M.K.; Chaudhary, B.; Akarsh, A.P.; Sah, B.
The rubble mound (RM) breakwater, which is a prevalent coastal structure worldwide, often faces the significant challenge of tsunami-induced damage. Coastal regions which are characterized by high population density necessitate robust breakwaters to withstand the destructive forces of tsunamis. The most devastating natural hazard that a breakwater could encounter during its lifespan is the tsunami. Past occurrences have revealed vulnerabilities in conventional RM breakwaters leading to failures attributed to the scouring of rubble and seabed caused by excessive seepage during tsunami overflow events. This study presents novel countermeasures aimed at mitigating the potential failure mechanisms induced by tsunamis on RM breakwaters. The proposed countermeasure elements include gabions, crown walls equipped with shear keys, and sheet piles. To assess the efficacy of these innovations, a series of tsunami overflow tests was conducted on small-scale models. The results demonstrated a marked improvement in the stability and resilience of RM breakwaters against tsunamis with the incorporation of these countermeasures. Additionally, numerical simulations were performed to determine the precise mechanisms influencing the behavior of the breakwater during tsunamis. © 2024 American Society of Civil Engineers.
Performance Assessment of Geosynthetic Reinforced Quay Walls under Concurrent Tsunami and Earthquake Aftershocks
(American Society of Civil Engineers (ASCE), 2025) Sajan, M.K.; Sah, B.; Chaudhary, B.; Akarsh, P.K.
Coastal structures are built against the dynamic loadings from waves, tides, and storms. However, natural disasters such as earthquakes and tsunamis can impart additional loadings on these structures that might exceed their design specifications. In the past, several earthquakes and tsunamis had resulted in severe damages even on coastal structures engineered to withstand tsunamis. It is reasonable to suggest that the tsunami waves succeeding the earthquake had impacted the coastal structures along with an aftershock, imparting the most critical loading conditions. However, limited studies are available, evaluating the performance of coastal structures when subjected to the combined loading conditions. Among various coastal structures, quay walls stand out due to their distinctive loading patterns, concurrently sustaining vertical live loads, active pressure from retained backfill, and dynamic wave forces from the sea. Therefore, the present study paper puts forth a comprehensive analysis of geosynthetic reinforced quays under the influence of a tsunami withdrawal and an earthquake aftershock. Since the magnitudes of seaward-directed loads during tsunami drawdown are unknown and difficult to assess practically, this study assumes a worst-case loading condition to represent these effects. The analytical approach adopted employs the horizontal slice method, encompassing the influence of outboard seawater, backfill submergence, tsunami impact, and pseudo-static earthquake loads. Results indicate that combined loading conditions substantially increase reinforcement forces, reducing the internal stability of quay walls. Critical parameters influencing stability include the shear strength of backfill soil, quay wall inclination, and surcharge loads. © 2025 American Society of Civil Engineers.

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