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This study investigated the mechanical performance, toughness behavior, failure characteristics, and microstructure of geopolymer-stabilized laterites modified with modified natural rubber latex (MNRL) for application in pavement base and subbase layers. Class C fly ash was used as the primary binder, with MNRL added at a weight% of 0–10% of the dry soil. Unconfined compressive strength ( q u ), indirect tensile strength ( q t ), and flexural strength ( q f ) were evaluated, alongside brittleness index (BI), improvement toughness ratio (ITR), and scanning electron microscopy (SEM). The results showed that while the addition of MNRL reduced peak q u by 20–60%, most mixtures still satisfied subbase ( q u > 0.70 MPa) and base ( q u > 1.75 MPa) strength criteria. MNRL significantly decreased BI (from 1.00 to as low as 0.03) and increased ITR (up to 6.28), indicating a transition from brittle to ductile failure. SEM analysis confirmed the formation of elastic polymer films that bridge fly ash and soil particles, thereby enhancing matrix cohesion and reducing porosity. The optimal mixture containing 25–30% fly ash and 5–7% MNRL achieved q u values of 1.83–2.64 MPa with improved ductility. The findings confirmed that MNRL effectively enhanced toughness and fracture resistance, making it a promising sustainable additive for laterite stabilization in tropical pavement infrastructure.

A tsunami is a natural disaster that destroys structures and kills many lives in many countries in the world. A risk assessment of the building under a tsunami loading is thus essential to evaluate the damage and minimize potential loss. A crucial tool in risk assessment is the fragility curve. Most building fragility curves for tsunami force were developed using survey building damaged data. This research proposed a method for developing fragility curves under tsunami loading based on the analytical building model data. In the development, the generic building was a one-story reinforced-concrete building with masonry-infilled walls constructed from the structural index, popularly built as residential buildings along the west coast of southern Thailand. Three damage levels were investigated: damage in masonry infill walls, damage in primary structures, and collapses. The masonry infill wall was modeled using multisprings to represent the load-bearing behavior due to tsunami with a hydrodynamic pattern. The fragility curves were developed using the maximum likelihood method and considering the uncertainty due to masonry infill wall type, tsunami flow direction, and tsunami flow velocity. The developed fragility curve agrees well with the empirical tsunami fragility curve of a one-story reinforced-concrete building damage data in Thailand from the 2004 Tsunami. The developed fragility functions could be adopted for assessing tsunami risk assessment and disaster mitigation for similar structures against different tsunami scenarios in the future.