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
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摘要
南京粉质黏土与粉砂互层土为粉质黏土与粉细砂交互沉积,呈现"千层饼"状外貌;南京粉细砂是一种以片状颗粒成分为主的粉细砂,与通常的圆形颗粒石英砂有一定区别,片状颗粒成分使得南京粉细砂具有各向异性的性质。利用南京工业大学岩土工程研究所自行研制的DSZ-1型动三轴仪对南京粉质黏土与粉砂互层土及粉细砂进行对比试验,对其试验成果进行分析,从中发现:在均压固结条件下,由于粉质黏土与粉砂互层土独特的结构性,其振动孔压发展模式与粉细砂的不同,可以用双曲线进行拟合,而粉细砂的振动孔压发展模式与Seed提出的砂土的振动孔压发展模式相同,可以用反正弦三角函数拟合;在偏压固结条件下,两者的振动孔压发展模式相同,均可以用双曲线进行拟合。此外,无论是均压固结还是偏压固结条件,对于粉质黏土与粉砂互层土,当以轴向双幅应变5%作为液化标准时,其发生液化的振动孔压均达不到围压值。
The interbedded strata of silty clay and fine sand in Nanjing is a sediment deposited alternately by silty clay and fine sand with its appearance as a " thousand layers cake".Nanjing fine sand mainly consists of schistous grains and is different from the standard sand with round quartz grains. Nanjing fine sand is anisotropic because of the schistous grain. By use of DSZ-1 dynamic triaxial apparatus made by Nanjing University of Technology, Nanjing silty clay interbedded with fine sand and Nanjing fine sand were tested. Through the analysis of these test results, the following conclusions are drawn.First, with isotropic consolidation, the development of dynamic pore water pressure in silty clay differs from that in fine sand because of the particular structure of interbedded with silty clay and fine sand and its curve can be fitted by hyperbola. However,the pore water pressure curve in fine sand is same as that advanced by Seed and can be fitted by arcsine function. Second, with anisotropic consolidation, there is similar development of dynamic pore water pressure in these two soils. Both of them can be fitted by hyperbola.Finally, whether in isotropic consolidation or in anisotropic consolidation, dynamic pore water pressure can not approach confining pressure when axial strain 5% is considered as the liquefaction standard of the interbedded strata of silty clay and fine sand .
The interbedded strata of silty clay and fine sand in Nanjing is a sediment deposited alternately by silty clay and fine sand with its appearance as a " thousand layers cake".Nanjing fine sand mainly consists of schistous grains and is different from the standard sand with round quartz grains. Nanjing fine sand is anisotropic because of the schistous grain. By use of DSZ-1 dynamic triaxial apparatus made by Nanjing University of Technology, Nanjing silty clay interbedded with fine sand and Nanjing fine sand were tested. Through the analysis of these test results, the following conclusions are drawn.First, with isotropic consolidation, the development of dynamic pore water pressure in silty clay differs from that in fine sand because of the particular structure of interbedded with silty clay and fine sand and its curve can be fitted by hyperbola. However,the pore water pressure curve in fine sand is same as that advanced by Seed and can be fitted by arcsine function. Second, with anisotropic consolidation, there is similar development of dynamic pore water pressure in these two soils. Both of them can be fitted by hyperbola.Finally, whether in isotropic consolidation or in anisotropic consolidation, dynamic pore water pressure can not approach confining pressure when axial strain 5% is considered as the liquefaction standard of the interbedded strata of silty clay and fine sand .
引文
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[2]陈国兴,胡庆兴,刘雪珠.关于砂土液化判别的若干意见[J].地震工程与工程振动,2002,(1):141-151.
[3]衡朝阳,何满潮,裘以惠.含黏粒砂土抗液化性能的试验研究[J].工程地质学报,2001,9(4):339-344.
[4]SeedHB,TokimatsuK,HarderLF,etal.TheinfluenceofSPTproceduresinsoilliquefactionresistanceevalutions[J].ASCE,1985,111(12),1425-1445.
[5]YoudTL,IdrissTM,etal.Liquefactionresistanceofsoils[J].ASCE,2001,127(8):817-833.
[6]周 镜.岩土工程中的几个问题[J].岩土工程学报,1999,2(1):2-8.
[7]陈国兴,朱定华,何启智,等.DSZ-1型动三轴试验机研制与性能试验[J].地震工程与工程振动,2002,(6):71-75.
[8]周 健,白 冰,段瑞明.粉煤灰作为筑坝排水垫层的动力特性试验研究[J].勘察科学技术,2000,(5):7-11.
[9]SeedHB,etal.Pore waterpressurechangesduringsoilliquefaction[J].ASCE,1976,112(GT4):327-346.
[10]陈国兴,谢君斐,韩 炜,等.土体地震反应分析的简化有效应力法[J].地震工程与工程振动,1995,(2):52-61.
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