受控三轴应力-应变下沉积物声速与物理力学性质的关系

对南海某海域深度100～400 m的海底浅层（约2 m埋深范围）沉积物柱状样在接近海底水压力下进行三轴应变-声学同步测量，结果表明沉积物纵波声速有两个特征:（1）从应变过程开始到结束，沉积物纵波声速不断变化；（2）平均声速随着平均静弹性模量的增加，由大变小又由小变大，存在声速最小值。这些结果与海底浅表层沉积物的物理力学性质、围压、颗粒的结合状态改变有关。此外，沉积物动弹性模量和孔隙度呈良好的负相关性，这与孔隙度增大含水量增大有关；动弹性模量是静弹性模量的10～100倍，这主要与三轴应变试验的应变数量级与声波振动产生的应变数量级的差异大有关。采用本论文实验测量的数据分别建立了双复合参数-声速和孔隙度-声速经验公式，分析结果表明双复合参数-声速公式声速预报误差约是孔隙度-声速公式的1/4，表明双复合参数-声速公式更加有效。

Relationship between sound velocity and physical mechanical properties of seafloor sediments in controlled three axis stress-strain

The sediment cores, from shallow seafloor in depth of 100-400 meters (about 2 m depth buried) in an area of the South China Sea, have been performed a simultaneous triaxial strain-acoustic measurement near seabed water pressure. The results show that the sediment longitudinal wave velocity has two characteristics: (1) the longitudinal wave velocity in sediments keeps changing in the process of strain applied from start to end; (2) the average of the speed of sound changes from large to small and then from small to large with the average of the static elastic modulus increasing, and there is a minimum during the course of the average of the speed of sound change. These results are related to physical and mechanical properties and confining pressure of the shallow seafloor sediments, and the changes of the state in which particles of these sediments combine together. In addition, sediment dynamic elastic modulus and porosity has a good negative correlation, and that results from increases of the water content with increases of porosity. Dynamic elastic modulus is 10 to 100 times the static elastic modulus, since the large difference between the strain magnitude resulted from triaxial strain-test and the one generated by wave vibrations is primarily related to that. Two empirical formulas of dual complex parameters-velocity and porosity-velocity were established with the experimentally measured data in this paper. The analysis of results shows that the error in sound speed predicted by the formula of composite double parameters-velocity is approximately a quarter of that predicted by the formula of the porosity-velocity, and it shows that the formula of composite double parameters-velocity is more effective.