港湾における鋼材腐食の研究 (第3報)

Abstract

Tie rod is the steel bar which is used to prevent steel sheet pile structures from destruction and fox convenience placed in sandy layer at tidal zone. Accordingly, tie rod is connected with steel in saturated sandy layer, that is, steel sheet pile below residual water level, and contacts with sandy layer which becomes alternately saturated by sea water at high water tide and unsaturated at low water tide.To secure the stability of steel pile structures, confirmation of corrosion rate of tie rod should be given. But, few corrosion survey of tie rod has been made because it is possible only when steel sheet pile structures are removed.Therefore, corrosion survey of tie rod at Toyama Harbor and Shimokita Pier and a laboratory experiment on corrosion mechanism of tie rod were made, and the following results were obtained:(1) Both tie rods, buried for 33 years at Toyama Harbor and for 40 years at Shimokita Pier, did almost not corrode.(2) According to the laboratory experiment, it is assumed that steel sheet pile below residual water level acts as anode while tie rod as cathode, and at low water tide galvanic current of about 0.032 A/m2, flows from anode to cathode while at high water tide current of about 0.023A/m2 flows.(3) If we expect (2), it is necessary that tie rod and steel sheet pile are in close contact.