循环预剪作用对饱和松砂抗液化强度影响
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摘要
利用土工静力-动力液压三轴-扭转多功能剪切仪,在均等固结条件下,针对福建标准砂(Dr=30%),进行了不同应力幅值的循环预剪试验和二次加载液化试验,探讨了波浪荷载的循环预剪作用对饱和砂土抗液化强度的影响.试验结果表明:循环预剪作用降低了饱和砂土孔隙比,但其影响程度较小.在较小的应力幅值范围和一定的循环次数内,循环预剪作用过程中所产生的最大孔隙水压力随着所施加的循环应力幅值的增加而呈线性的增长.在循环预剪过程中饱和砂土未发生液化条件下,随着循环预剪应力幅值的增加,饱和砂土的抗液化强度也不断得到提高.分析其原因,主要是在施加循环预剪作用时,饱和砂土孔隙的均匀化过程和砂土颗粒间咬合作用的增强,使砂土形成了较为稳定的结构.
A series of tests were performed,including the cyclic preloading tests with different stress magnitudes and the second loading liquefaction tests on Fujian saturated loose sands with a relative density of 30% under isotropic consolidation condition by using the soil static and dynamic universal triaxial and torsional shear apparatus.And the effect of the cyclic preloading on the resistance to liquefaction of saturated loose sands was investigated.Experimental data indicate that the void ratio of saturated sands has a negligible reduction after cyclic preloading.And in the given cyclic numbers the maximal pore water pressure during the cyclic preloading increases linearly with the increment of cyclic stress magnitude which is small.Moreover,with the increment of the cyclic preloading stress magnitude,the resistance to liquefaction of saturated sands in the second loading is increased continuously under the condition that the liquefaction does not occur during the cyclic preloading.The reason is that more stable structure is constructed because of the uniformity of the void and the better interlocking of the particles when the cyclic preloading is performed on the saturated sands.
A series of tests were performed,including the cyclic preloading tests with different stress magnitudes and the second loading liquefaction tests on Fujian saturated loose sands with a relative density of 30% under isotropic consolidation condition by using the soil static and dynamic universal triaxial and torsional shear apparatus.And the effect of the cyclic preloading on the resistance to liquefaction of saturated loose sands was investigated.Experimental data indicate that the void ratio of saturated sands has a negligible reduction after cyclic preloading.And in the given cyclic numbers the maximal pore water pressure during the cyclic preloading increases linearly with the increment of cyclic stress magnitude which is small.Moreover,with the increment of the cyclic preloading stress magnitude,the resistance to liquefaction of saturated sands in the second loading is increased continuously under the condition that the liquefaction does not occur during the cyclic preloading.The reason is that more stable structure is constructed because of the uniformity of the void and the better interlocking of the particles when the cyclic preloading is performed on the saturated sands.
引文
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[11]苏栋,李相崧.地震历史对砂土抗液化性能影响的试验研究[J].岩土力学,2006,27(10):1815-1818
[2]FINN D W L,BRANSBY P L,PICHERING D J.Effect of strain history on liquefaction of sand[J].Journal of the Soil Mechanics and FoundationsDivision,1970,96(6):1917-1933
[3]ISHI HARA K,OKADA S.Effect of stress historyon cyclic behavior of sand[J].Soil and Foundations,1978,18(4):31-45
[4]SUZUKI T,TOKI S.Effects of preshearing onliquefaction characteristics of saturated sand subjectedto cyclic loading[J].Soils and Foundations,1984,24(2):16-28
[5]EMERYJ J,FINN W D L,LEE K W.Uniformityof saturated sand speci men[M]//Evaluation ofRelative Density and Its Role in Geotechnical ProjectsInvolving Cohesionless Soils.Philadelphia:ASTM,1973:182-194
[6]ODA M,KAWAMOTO K,SUZUKI K,et al.Microstructural interpretation on reliquefaction ofsaturated granular soils under cyclic loading[J].Journal of Geotechnical and GeoenvironmentalEngineering,2001,127(5):416-423
[7]WICHTMANN T,NIEMUNIS A,TRIANTAFYLLIDIS T,et al.Correlation of cyclicpreloading with the liquefaction resistance[J].SoilDynamics and Earthquake Engineering,2005,25(12):923-932
[8]BAS B M.土动力学原理[M].吴世明,顾尧章,译.杭州:浙江大学出版社,1984
[9]BHATIA S K,SOLI MAN A F.Frequencydistribution of void ratio of granular materialsdetermined by an i mage analyzer[J].Soils andFoundations,1990,30(1):1-16
[10]沈珠江.复杂荷载下砂土液化变形的结构性模型[C]//第五届全国土动力学学术会议论文集.大连:大连理工大学出版社,1998:1-10
[11]苏栋,李相崧.地震历史对砂土抗液化性能影响的试验研究[J].岩土力学,2006,27(10):1815-1818
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