考虑场地动应力条件的饱和海洋粉细砂液化特性

Experimental study on liquefaction characteristics of saturated marine silty fine sand considering site dynamic stress conditions

确保地震荷载作用下海床场地的动力稳定性是海洋工程全寿命周期安全运行的重要保证,然而对复杂海域环境下饱和粉细砂的液化特性研究尚属少见。基于海域场地动应力计算方法,确定各试验工况的场地循环应力比CSR,并对试样施加与之对应的不排水循环荷载。试验结果表明:可液化的海洋粉细砂在考虑其场地动应力条件的循环荷载作用下出现不同的液化可能性;粉细砂呈循环破坏模式,将双幅轴向应变>5%作为循环破坏标准;海洋粉细砂的液化可能性与土体的埋深及动应力均不呈单一相关性,而是随着干密度的增大,液化振次逐渐增大,当干密度>1.72 g/cm^(3)时土体不再液化。该结果可为杭州湾区抗震区划及海洋工程结构抗震设计提供参考。

To ensure the dynamic stability of seabed site under seismic load is an important guarantee for the safe operation of marine engineering during the whole life cycle.Research on the liquefaction characteristics of saturated silty fine sand in complex marine environment has been rare.Based on the dynamic stress calculation method of marine site,the site cyclic stress ratio(CSR)of each test condition was determined,and the corresponding undrained cyclic loading was applied to the sample.The results show that the liquefaction possibilities of marine silty fine sand are different under cyclic loading considering the dynamic stress condition of the site.The silty fine sand presents a cyclic failure mode,and the double-amplitude axial strain exceeding 5%is taken as the cyclic failure criterion.The liquefaction possibility of marine silty fine sand has no single correlation with the buried depth and dynamic stress of soil.With the increase of dry density,the liquefaction frequency increases gradually.When the dry density is greater than 1.72 g/cm^(3),the soil is no longer liquefied.The results can provide referrence for anti-seismic zoning and anti-seismic design of marine engineering structures in Hangzhou Bay.