受控三轴应力-应变下沉积物声速与物理力学性质的关系
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摘要
对南海某海域深度100~400m的海底浅层(约2m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。
The sediment cores,from shallow seafloor in depth of 100-400meters(about 2mdepth 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 100times 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 aquarter of that predicted by the formula of the porosity-velocity,and it shows that the formula of composite double parameters-velocity is more effective.
The sediment cores,from shallow seafloor in depth of 100-400meters(about 2mdepth 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 100times 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 aquarter of that predicted by the formula of the porosity-velocity,and it shows that the formula of composite double parameters-velocity is more effective.
引文
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[12]国家质量技术监督局,中华人民共和国建设部.GB/T 50123-1999,土工试验方法标准[S].北京:中国计划出版社,2007.The State Bureau of Quality and Technical Supervision,Ministry of Construction of the People's Republic of China.Soil Test Method Standard(GB/T50123-1999)[S].Beijing:China Planning Publishing House,2007.
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[16]Mavko G,Mukerji T,Dvorkin J.The rock physics handbook:tools for seismic analysis in porous media[M].London:Cambridge University Press,2003.
[2]Stoll R D,Sun Yuefeng,Bitte I.Seafloor properties from penetrometer tests[J].IEEE Journal of Oceanic Engineering,2007,32(1):57-63.
[3]Lu Bo,Li Ganxian,Huang Shaojian,et al.The three results of sound velocity variance in sediments during controlled stress-strain testing from the South China Sea[J].Marine Georesources and Geotechnology,2002,20(3):177-186.
[4]Chen Minpen,Shieh Y T,Chyan J M.Acoustic and physical properties of surface sediments in northern Taiwan strait[J].Acta Oceanographica Taiwanica,1988(21):92-118.
[5]Hamilton E L,Bachman R T.Sound velocity and related properties of marine sediments[J].Journal of Acoustical Society of America,1982,72(6):1891-1904.
[6]Hamilton E L.Geoacoustic modeling of the sea floor[J].Journal of Acoustical Society of America,1980,68(5):1313-1340.
[7]Anderson R S.Statistical correlation of physical properties and sound velocity in sediments[M]//Hampton L.Physics of Sound in Marine Sediments.US:Springer,1974:48l-5l8.
[8]卢博,李赶先,孙东怀,等.中国东南近海海底沉积物声学物理性质及其相关关系[J].热带海洋学报,2006,25(2):12-17.Lu Bo,Li Ganxian,Sun Donghuai,et al.Acoustic-physical properties of seafloor sediments from nearshore southeast China and their correlations[J].Journal of Tropical Oceanography,2006,25(2):12-17.
[9]龙建军,李赶先.海底沉积物声速与物理性质的理论关系[J].声学学报,2015,40(3):462-468.Long Jianjun,Li Ganxian.Theoretical relations between sound velocity and physical-mechanical properties for seafloor sediments[J].Acta Acustica,2015,40(3):462-468.
[10]龙建军,李赶先,邹大鹏.海底沉积物纵波波速与物理-力学性质的理论关系和比较[J].海洋学报,2014,36(7):111-117.Long Jianjun,Li Ganxian,Zou Dapeng.Theoretical relations of longitudinal wave velocity and physical-mechanical properties for seafloor sediments and comparison[J].Haiyang Xuebao,2014,36(7):111-117.
[11]朱思哲,刘虔,包承纲,等.三轴试验原理与应用技术[M].北京:中国电力出版社,2003.Zhu Sizhe,Liu Wen,Bao Chenggang,et al.Three Axis Test Principle and Application Technology[M].Beijing:China Power Press,2003.
[12]国家质量技术监督局,中华人民共和国建设部.GB/T 50123-1999,土工试验方法标准[S].北京:中国计划出版社,2007.The State Bureau of Quality and Technical Supervision,Ministry of Construction of the People's Republic of China.Soil Test Method Standard(GB/T50123-1999)[S].Beijing:China Planning Publishing House,2007.
[13]刘寄能,梁元博,卢博,等.南海两海区海底沉积物的声速和应力-应变特征[J].南海海洋科学刊,1989(9):87-94.Liu Jineng,Liang Yuanbo,Lu Bo,et al.Acoustic velocity and stress-strain characteristics of seabed sediments in two areas of South China Sea[J].The Volume of South China Sea Marine Science,1989(9):87-94.
[14]Hamilton E L.Elastic properties of marine sediments[J].Journal of Geophysical Research,1971,76(2):579-604.
[15]Hamilton E L.Vp/Vs and Poisson's ratios in marine sediments and rocks[J].Journal of Acoustical Society of America,1979,66(4):1093-1101.
[16]Mavko G,Mukerji T,Dvorkin J.The rock physics handbook:tools for seismic analysis in porous media[M].London:Cambridge University Press,2003.