饱和珊瑚砂体应变发展模式与预测模型试验研究

Experimental study on development patterns of volumetric strain and predictive modeling for saturated coral sands

珊瑚砂具有较好的排水条件,地震、波浪荷载作用下饱和珊瑚砂产生的排水变形易引起海床和附近结构物的破坏。利用GDS循环三轴仪,针对南沙岛礁饱和珊瑚砂试样进行了一系列循环排水加载试验,以探究细粒含量FC、相对密度D_r及循环应力比CSR对饱和珊瑚砂变形特性的影响。试验结果表明,饱和珊瑚砂的累积体应变ε_(vp)的发展速率和变形程度随FC、CSR的增大而增大,随D_(r)的增大而减小。饱和珊瑚砂ε_(vp)-N关系曲线呈现出循环平稳和循环蠕变两种发展模式。引入潜在破坏系数DP表征FC对ε_(vp)发展模式的影响,建立了DP×CSR-D_(r)框架的饱和珊瑚砂体应变发展模式评价方法。为表征FC及D_(r)对饱和珊瑚砂ε_(vp)-N关系曲线的影响,引入了骨架孔隙比e_(sk)*,发现两种发展模式下ε_(vp-s)与e_(sk)*均存在良好的相关性,遂建立了排水循环加载条件下饱和珊瑚砂的体应变发展模型,可以较好地预测饱和珊瑚砂的累积体应变发展规律。

The coral sand has better drainage conditions,and the drainage deformation of the saturated coral sand under earthquake and wave loads can easily cause damage to the seabed and nearby structures.Focusing on the properties of the saturated coral sand and by investigating the effects of fines content FC,relative density Dr and cyclic stress ratio CSR on its deformation characteristics,a series of cyclic drainage loading tests are carried out on the specimens of Nansha islands using the GDS dynamic triaxial instrument.The test results show that the development rate and the degree of deformation of cumulative volumetric strainεvp of the coral sand increase with the increase of FC and CSR,and decrease with the increase of Dr.Theεvp-N relationship curve of the saturated coral sand shows two development modes,cyclic smoothness and cyclic creep.The potential damage factor DP is introduced to characterize the influences of FC on the development pattern ofεvp,and a DP×CSR-Dr framework is established to evaluate the development patterns of its volumetric strain.To characterize the effects of FC and Dr on itsεvp-N relationship curve,the equivalent skeleton void ratio esk*is introduced,and it is found that there is a good correlation betweenεvp-s and esk*under both development modes,thus,a model for the development of volumetric strain in the saturated coral sand under drainage cyclic loading conditions is established,which can well predict the development patterns of volumetric strain in the saturated coral sand.