Impact of Dredging on Coastal Infrastructure: Case Studies from Okrika and Port Harcourt, Niger Delta  

作　　者：Tamunoene Kingdom Simeon Abam Ferdinand Dumbari Giadom Robert Egwu Otu Iduma Tamunoene Kingdom Simeon Abam;Ferdinand Dumbari Giadom;Robert Egwu Otu Iduma(Geotechnics Section, Institute of Geosciences and Environmental Management, Rivers State University, Nkpolu, Port Harcourt, Nigeria;Department of Geology, University of Port Harcourt, Choba, Port Harcourt, Nigeria;Department of Surveying and Geoinformatics, Akanu Ibiam Federal Polytechnic, Unwana, Nigeria)

机构地区：[1]Geotechnics Section, Institute of Geosciences and Environmental Management, Rivers State University, Nkpolu, Port Harcourt, Nigeria [2]Department of Geology, University of Port Harcourt, Choba, Port Harcourt, Nigeria [3]Department of Surveying and Geoinformatics, Akanu Ibiam Federal Polytechnic, Unwana, Nigeria

出　　处：《Journal of Geoscience and Environment Protection》2023年第5期349-362,共14页地球科学和环境保护期刊（英文）

摘　　要：Sand excavations in river beds have compromised the safety of several bridges in recent years. Large scale sand mining from river beds is now common in the Niger Delta, due to the necessity of reclaiming land for development purposes and to meet construction needs in the region. There is currently no regulation as to where sand can be mined in river channels because of the lack of adequate understanding of the risks to coastal infrastructure involved with its abstraction. The phenomenon of bridge Abutment and bank failure induced by excessive dredging of sand river bed is considered. Two types of instability were distinguished, one relating to the equilibrium slope of the riverbed and the other riverbank instability. An empirical relationship in the form X_s = 3Htan(90 - α) has been developed through analysis, supported by examples that a minimum distance of 94 m (for sand river beds) from a bridge should be observed for sand abstraction in order to guaranty the safety of bridge foundation. For clay riverbeds, slightly shorter minimum distances can be considered safe. The study further shows that the capacity of sand borrowing in river channels to generate bank instability is dependent on the composition and stratigraphy beneath the river bed.Sand excavations in river beds have compromised the safety of several bridges in recent years. Large scale sand mining from river beds is now common in the Niger Delta, due to the necessity of reclaiming land for development purposes and to meet construction needs in the region. There is currently no regulation as to where sand can be mined in river channels because of the lack of adequate understanding of the risks to coastal infrastructure involved with its abstraction. The phenomenon of bridge Abutment and bank failure induced by excessive dredging of sand river bed is considered. Two types of instability were distinguished, one relating to the equilibrium slope of the riverbed and the other riverbank instability. An empirical relationship in the form X_s = 3Htan(90 - α) has been developed through analysis, supported by examples that a minimum distance of 94 m (for sand river beds) from a bridge should be observed for sand abstraction in order to guaranty the safety of bridge foundation. For clay riverbeds, slightly shorter minimum distances can be considered safe. The study further shows that the capacity of sand borrowing in river channels to generate bank instability is dependent on the composition and stratigraphy beneath the river bed.

关 键 词：DREDGING IMPACTS Coastal Infrastructure Niger Delta 

分 类 号：P53[天文地球—古生物学与地层学]