不同河水流速下沉管隧道混凝土劣化机理研究OA

During the construction and service life of inland immersed tube tunnels,the tunnel concrete is subjected to multi-field coupled loads including ionic erosion from river water(chemical field),overlying soil overburden and hydrostatic pressure(stress field),as well as hydrodynamic scouring induced by river flow(seepage field).These coupled actions degrade the me-chanical properties of immersed tube tunnel concrete,thereby threatening structural safety and shortening the service life of the tunnel.Taking the inland immersed tube tunnel on Lungui Road,Shunde District as the research object,long-term stress-seep-age-chemical coupled erosion tests on concrete under different flow velocities were carried out in this paper.Millimeter indenta-tion testing was adopted to quantify the degradation law of mechanical performance of the structural concrete,and scanning elec-tron microscopy(SEM)combined with mineralogical analysis was utilized to reveal the influence mechanism of flow velocity on concrete deterioration.The results show that the elastic modulus of structural concrete for inland immersed tube tunnels under river erosion rises initially and then declines,which is mainly attributed to the content variation of reaction products such as gypsum,ettringite and Friedel's salt.Rising flow velocity accelerates concrete erosion;the erosion depth increases from 4.42 mm under static water to 5.66 mm at a flow velocity of 0.06 m/s,while the erosion rate rises from 0.0587 mm/d to 0.0783 mm/d.Higher flow velocity aggravates concrete deterioration;as the flow velocity increases from 0 to 0.6 m/s,the elastic modulus near the ero-sion surface drops from 17.86 GPa to 16.41 GPa.The research findings can provide technical references for the design,construc-tion and maintenance of inland immersed tube tunnels.