2024-04-03 ヒューストン大学(UH)
＜関連情報＞
- https://www.uh.edu/nsm/earth-atmospheric/news-events/stories/2024/0403-inelastic-subsidence.php
- https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2023GL107549
隠された脅威を解き明かす： 干ばつによる膨張性土壌の非弾性沈下 Unveiling the Hidden Threat: Drought-Induced Inelastic Subsidence in Expansive Soils
Jennifer Welch, Guoquan Wang, Yan Bao, Shuangcheng Zhang, Guanwen Huang, Xie Hu
Geophysical Research Letters Published: 29 March 202
DOI:https://doi.org/10.1029/2023GL107549
Abstract
Expansive soils pose a significant challenge in geotechnical engineering, especially in coastal areas. While research has mainly focused on their elastic properties, this study explores the overlooked aspect of inelastic subsidence during prolonged droughts, utilizing decade-long GPS datasets from the University of Houston Coastal Center. Our findings reveal substantial subsidence, approximately one to two dm, during the summer droughts of 2018, 2020, 2022, and 2023, due to compaction within the upper 4 m of expansive soils. Inelastic subsidence constitutes roughly 10% of the total subsidence, resulting in step-like permanent land elevation loss over time. Notably, drought-induced subsidence is prominent in open-field areas with expansive soils but is minor in built-up areas or in non-expansive soil regions. The occurrence of inelastic subsidence challenges traditional assessments of relative sea-level rise and coastal flooding, emphasizing the need to consider it in coastal infrastructure planning for enhanced resilience against climate uncertainties.
Key Points
- Prolonged droughts cause up 2 dm of subsidence in shallow expansive soils (<4 m deep) in Galveston, TX, 10% of which is inelastic
- Prolonged droughts lead to notable subsidence in open fields with expansive soils, but less in built-up areas or non-expansive soil areas
- Recurring droughts lead to permanent land elevation losses in open-field coast, possibly skewing sea-level rise and flood risk projections
Plain Language Summary
Expansive soils, often found in coastal regions, are known for causing issues like land shifts and unstable buildings. Our research adds a new dimension: prolonged droughts can lead to significant, irreversible sinking of expansive soils, permanently lowering the elevation of open land areas. Using a decade of GPS data, we found that during droughts, these soils can sink considerably and will not fully recover. Interestingly, in developed regions where pavement covers the soils, thereby minimizing moisture loss, this sinking is observed to be minimal. In the Galveston coastal area, drought-induced sinking can reach one to two dm, with irreversible subsidence making up about 10% of the total subsidence. This becomes a growing concern as droughts become more frequent due to climate change, especially in coastal areas. Additionally, our results suggest that current methods for estimating sea-level rise may be missing a key factor: we have underestimated the speed at which uninhabited coastal lands are sinking because we did not account for this irreversible sinking due to droughts.
