主应力轴旋转下高偏压固结粉土动力特性
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摘要
为研究不同固结方式对粉土在波浪荷载引起主应力轴循环旋转下的性状影响,对长江入海口相对密实度为70%的饱和粉土进行试验。采用空心圆柱仪对重塑粉土试样,进行了固结比为1和2条件下,恒定剪应力幅值的主应力轴循环旋转动力加载,并对相关孔压、应变等数据进行数值拟合分析。结果表明,主应力轴旋转下,固结比为1的试样,随动剪应力增大,孔压开展由三阶段两相态点模式转化为二阶段单相态点模式,而主应变差则在0.2%～0.5%这一小应变范围内发生崩塌;固结比为2的试样,孔压开展仅有二阶段单相态点模式,且孔压比至0.45保持稳定,主应变差则能平稳开展至较大幅值,比等向固结试样有更高动强度。最后采用修正Seed模型及双曲线模型分别对等压及偏压固结试样的孔压开展进行了预测。研究结果较好地揭示了不同固结比粉土在主应力轴旋转下的宏观性状差异。
To assess the influence of consolidation ratio(Kc) on silt's behaviors under cyclic principal stress rotation(CPSR),experiments were conducted on silt with the relative density of 70%.The remoulded silt samples with Kc=1 and 2 were tested with hollow cylinder apparatus.They underwent the CPSR stress paths with constant shear stress.And the characteristics of the pore pressure and strain were also analyzed with numerical method.The results show that under CPSR as for the samples with Kc=1,before failure the development of the pore pressure changes from three-stage mode into two-stage mode with the increase of shear stress.As to the strain,the maximum deviator strain is limited within 0.2% to 0.5% at the collapse points.While Kc=2,the pore pressure belongs to two-stage mode and its ratio remains stable at the value of around 0.45.As a result,the strain can generate smoothly to large extent and the samples have higher dynamic strength than the ones with Kc=1.Eventually,the development of the pore pressure of the samples with Kc=1 and 2 were respectively predicted by the modified Seed model and hyperbolic model.The research reveals the different macro-behaviors of silt under CPSR with different Kc effectively.
To assess the influence of consolidation ratio(Kc) on silt's behaviors under cyclic principal stress rotation(CPSR),experiments were conducted on silt with the relative density of 70%.The remoulded silt samples with Kc=1 and 2 were tested with hollow cylinder apparatus.They underwent the CPSR stress paths with constant shear stress.And the characteristics of the pore pressure and strain were also analyzed with numerical method.The results show that under CPSR as for the samples with Kc=1,before failure the development of the pore pressure changes from three-stage mode into two-stage mode with the increase of shear stress.As to the strain,the maximum deviator strain is limited within 0.2% to 0.5% at the collapse points.While Kc=2,the pore pressure belongs to two-stage mode and its ratio remains stable at the value of around 0.45.As a result,the strain can generate smoothly to large extent and the samples have higher dynamic strength than the ones with Kc=1.Eventually,the development of the pore pressure of the samples with Kc=1 and 2 were respectively predicted by the modified Seed model and hyperbolic model.The research reveals the different macro-behaviors of silt under CPSR with different Kc effectively.
引文
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[2]郭莹,栾茂田,何杨,等.复杂应力条件下饱和松砂孔隙水压力增长特性的试验研究[J].地震工程与工程振动,2004,24(3):139-144.GUO Ying,LUAN Mao-tian,HE Yang,et al.Experi-mental study on development pattern of shaking-in-duced pore water pressure of saturated loose sand un-der complex loading[J].Earthquake Engineering andEngineering Vibration,2004,24(3):139-144.(in Chi-nese).
[3]栾茂田,许成顺,郭莹,等.静力与动力组合应力条件下饱和松砂变形特性的试验研究[J].土木工程学报,2005,38(3):81-86,93.LUAN Mao-tian,XU Cheng-shun,GUO Ying,et al.An experimental study on the deformation characteris-tics of saturated loose sand under coupled static anddynamic combined stress conditions[J].China CivilEngineering Journal,2005,38(3):81-86,93.(in Chi-nese).
[4]YOSHIMINE M,ISHIHARA K,VARGAS W.Effects of principal stress direction and intermediateprincipal stress on undrainded shear behavior of sand[J].Soils and Foundations,1998,38(3):179-188.
[5]SASSA S,SEKIGUCHI H.Analysis of wave inducedliquefaction of sand beds[J].Geotechnique,2001,51(2):115-126.
[6]YANG Zhong-xuan,LI Xiang-song,YANG Jie.Und-rained anisotropy and rotational shear in granular soil[J].Geotechnique,2007,57(4):371-384.
[7]钱寿易,杜金声,楼志刚,等.海洋土力学现状及发展[J].力学进展,1980,20(4):1-14.QIAN Shou-yi,DU Jin-shen,LOU Zhi-gang,et al.Current situation and development of marine soil me-chanics[J].Advances In Mechanics,1980,20(4):1-14.(in Chinese).
[8]沈瑞福,王洪瑾,周景星.动主应力轴连续旋转下砂土的动强度[J].水利学报,1996,41(1):27-33.SHEN Riu-fu,WANG Hong-jin,ZHOU Jing-xing.Dynamic strength of sand under cyclic rotation of prin-cipal stress directions[J].Journal of Hydraulic Engi-neering,1996,41(1):27-33.(in Chinese).
[9]ALARCON-GUZMAN A,LEONARDS G A,CHA-MEAU J L.Undrained monotonic and cyclic strengthof sands[J].Journal Geotechnical Engineering,ASCE,1988,114(10):1089-1109.
[10]GEORGIANNOU V N,TSOMOKOS A.STAVROUK.Monotonic and cyclic behaviour of sand under tor-sional[J].Geotechnique,2008,58(2):113-124.
[11]SEED H B,IDISS I M.Pore water pressure changesduring soil liquefaction[J].ASCE,1976,112(GT4):327-346.
[12]陈国兴,刘雪珠.南京粉质黏土与粉砂互层土及粉细砂的振动孔压发展规律研究[J].岩土工程学报,2004,26(1):79-82.CHEN Guo-xing,LIU Xue-zhu.Study on dynamicpore water pressure in silty clay inter bedded with finesand of nanjing[J].Chinese Journal of GeotechnicalEngineering,2004,26(1):79-82.(in Chinese).
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