دانلود رایگان مقاله انگلیسی آسیب پذیری چندگانه سازه ها و شاهراه ها به علت زمین لرزه Gorkha و سیلاب نپال - الزویر 2018

Abstract

The 2015 Gorkha earthquake caused severe damage to structures in central Nepal. In 2017, a flash flood event occurred in the same area affected by the Gorkha earthquake and aggravated the damage to structures and lifelines. The present paper reports the damage of structures and lifelines subjected to multi-hazards in the affected area in central Nepal. Field investigations were performed after the Gorkha earthquake as well as the 2017 Chhatiune Khola flash flood. Specifically, damage associated with bridges, vernacular stone masonry buildings, roads, water supply systems, irrigation canals, electric poles, and road signs was assessed. Field measurement in terms of flow height was recorded in the case of vernacular buildings, and depth-damage curve due to the flash flood is depicted in this study. We have outlined the multi-hazards vulnerability of vernacular stone masonry buildings along the river banks susceptible to flash floods in this study. Moreover, a quantified damage scenario due to a strong earthquake and a flash flood is highlighted using field records.

5. Conclusions

Effect of independent multi-hazards on structures and lifelines is studied forensically in this paper. Due to the rarity of notable independent multi-hazards, possible future damage scenarios are not well known as in the case of single events like earthquakes, floods, and landslides. To this end, the multi-hazards vulnerability analysis is gaining more attention globally and one of the notable examples was envisaged in central Nepal after the 2015 Gorkha earthquake and 2017 Chhatiune Khola flash flood. The sum of our observations highlights that the vernacular buildings in Nepal may suffer the damage aggravation up to 300% in the case of the earthquake followed by the flash flood. Various damage states (minor, major, severe, and collapse) and the damage extents (damage percentage based on visual inspection) are presented in terms of the depth-damage curve. The derived curve was compared with the depth-damage curve for Asian residential buildings. Our comparison depicts that Nepali vernacular buildings collapse at a lower depth than the other Asian counterparts whereas the damage extent at relatively lower depth is usually lower than other Asian residential buildings. The reason behind such lower damage could be attributed to short period of inundation due to terrain characteristics, whereas, in the case of higher depth of inundation, due to inherent vulnerability and extended use without any periodic repairs, collapse should have occurred at lower depth of inundation than in the case of other Asian residential buildings. Damage to bridge, roadway, roadway signals, electrical poles, and water supply in the case of multi-hazards are systematically presented in this study. As bridges in Nepal are designed providing free boards and this approach is not found to be fully rational in the changing climate when considering flash floods; improvements in design approaches are required in near future to downscale the damage to the superstructures of bridges. The depth-damage curves are derived in this study using small sample of damage occurrence, so further investigation is required for exhaustive comparison with the other curves Being first of its type, this study focuses mostly on forensic approaches, however, numerical models can be incorporated in the future studies.