南京砂强度特征与静态液化现象分析
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摘要
在松散、中密和密实状态下,以南京粉细砂三轴固结不排水试验结果为基础,进行了强度、变形与静态液化特征的分析。松散南京砂强度特性表现出典型的应变软化,当轴向变形小于1%时强度达到最大值,而后急剧降低;在50,100 kPa围压时发生了静态液化。但随着固结压力的增大,静态液化消失。与南京砂具有相同土骨架的松散纯净砂却在低围压下未出现静态液化,其形成机制是:粉粒的存在未使土体孔隙比发生较大变化,却引起更大的体缩性;中密和密实南京粉细砂表现出加工硬化的强度特征,临界应力状态线倾角高达55°,具有较高的抗静态液化能力。
Undrained triaxial compression tests were performed on these reconstituted samples of Nanjing sands at three different relative densities and the results of an experimental study are presented.All tests were performed under monotonic loading.It is evaluated and analyzed to the stress-strain relationship and the probability of the static liquefaction.At low densities,samples exhibited typical strain-soften characteristics,in which peak strength arrived when the axial strain was below 1%;then deviator stress decreased rapidly.Moreover undrained triaxial tests showed static liquefaction(zone stress difference) at the confining pressure of 50kPa and 100kPa.As confining pressure were increased,static liquefaction disappeared and the effective stress paths indicated increasing resistance to liquefaction.Compared with Nanjing fine sand,clean sand,which has no fine granular,didn’t exhibit the static liquefaction at low confining pressure.So it is hypothesized that the presence of fines(particles smaller than 0.075mm) in the soil structure doesn’t bring out the notable changes of and,but provides the highly compressibility.At media dense and dense Nanjing sand show the strain-harden characteristics,and the slope of critical stress path arrives 55°with high resistances of static liquefaction.
Undrained triaxial compression tests were performed on these reconstituted samples of Nanjing sands at three different relative densities and the results of an experimental study are presented.All tests were performed under monotonic loading.It is evaluated and analyzed to the stress-strain relationship and the probability of the static liquefaction.At low densities,samples exhibited typical strain-soften characteristics,in which peak strength arrived when the axial strain was below 1%;then deviator stress decreased rapidly.Moreover undrained triaxial tests showed static liquefaction(zone stress difference) at the confining pressure of 50kPa and 100kPa.As confining pressure were increased,static liquefaction disappeared and the effective stress paths indicated increasing resistance to liquefaction.Compared with Nanjing fine sand,clean sand,which has no fine granular,didn’t exhibit the static liquefaction at low confining pressure.So it is hypothesized that the presence of fines(particles smaller than 0.075mm) in the soil structure doesn’t bring out the notable changes of and,but provides the highly compressibility.At media dense and dense Nanjing sand show the strain-harden characteristics,and the slope of critical stress path arrives 55°with high resistances of static liquefaction.
引文
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[6]中华人民共和国水利部.土工试验规程SL237-1999[S].北京:中国水利水电出版社,1999.
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[8]MROZ Z,BOUKPETI N,DRESCHER A.Constitutive model for static liquefaction[J].International Journal of Geomechanics,2003,3(2):133-144.BOUKETI N,MROZ Z,Drescher A.A model for static liquefaction in triaxial compression and extension[J].Canadian Geotechnical Journal,2002,39:1 243-1 253.
[10]BISHOP A W.Progressive failure—with special reference to mechanism causing it[C]//Proceedings of the Geo-technical Conference,Norway:Oslo,1967,2:142-150.
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[12]YAMAMURO J A,LADE P V.Static liquefaction of very loose sands[J].Canadian Geotechnical Journal,1997,34:905-917.
[13]LADE P V,YAMAMURO J A.Effects of nonplastic fines on static liquefaction of sands[J].Canadian Geotechnical Journal,1997,34:918-928.
[14]YAMAMURO J A,COVERT K M.Monotonic and cyclic liquefaction of very loose sands with high silt content[J].Journal of Geotechnical and Geoenvironmental Engineering,2001,127(4):314-324.
[15]TERZAGHI K,PECK R B.Soil Mechanics in engineering practice(3rd edition)[M].New York:John Wiley&Sons Inc.,1996.
[16]谢定义.饱和砂土体液化的若干问题[J].岩土工程学报,1992,14(3):90-98.XIE Ding-yi.Some problems of liquefaction of the saturated sand[J].Chinese Journal of Geotechnical Engineering,1992,14(3):90-98.
[17]ZHANG Hui-ming,GARGA V K,ZENG Qiao-ling.Steady state strength of sand:concepts and experiment[J].Chinese Journal of Geotechnical Engineering,1999,21(2):230-235.张惠明,GARGA V K,曾巧玲.Steady state strength of sand:concepts and experiment[J].岩土工程学报,1999,21(2):230-235.
[2]黄永林.南京砂的液化与判别[J].世界地震工程,2001,17(1):69-74 HUANG Yong-lin.Liquefaction of the Nanjing sand and its identification[J].World Information on Earthquake Engineering,2001,17(1):69-74.
[3]FOURIE A B,BLIGHT G E,PAPAGEORGIOU G.Static liquefaction as a possible explanation for the Merriespruit tailings dam failure[J].Canadian Geotechnical Journal,2001,38(4):707-719.
[4]ISHIHARA K.Liquefaction and flow failure during earthquakes[J].Geotechnique,1993,43(3):351-415.
[5]YAMAMURO J A,LADE P V.Static liquefaction of very loose sands[J].Canadian Geotechnical Journal,1997,(34):905-917.
[6]中华人民共和国水利部.土工试验规程SL237-1999[S].北京:中国水利水电出版社,1999.
[7]黄文熙.土的工程性质[M].北京:水利电力出版社,1983.
[8]MROZ Z,BOUKPETI N,DRESCHER A.Constitutive model for static liquefaction[J].International Journal of Geomechanics,2003,3(2):133-144.BOUKETI N,MROZ Z,Drescher A.A model for static liquefaction in triaxial compression and extension[J].Canadian Geotechnical Journal,2002,39:1 243-1 253.
[10]BISHOP A W.Progressive failure—with special reference to mechanism causing it[C]//Proceedings of the Geo-technical Conference,Norway:Oslo,1967,2:142-150.
[11]PITMAN T D,ROBERTSON P K,SEGO D C.Influence of fines on the collapse of loose sands[J].Canadian Geotechnical Journal,1994,31:728-739.
[12]YAMAMURO J A,LADE P V.Static liquefaction of very loose sands[J].Canadian Geotechnical Journal,1997,34:905-917.
[13]LADE P V,YAMAMURO J A.Effects of nonplastic fines on static liquefaction of sands[J].Canadian Geotechnical Journal,1997,34:918-928.
[14]YAMAMURO J A,COVERT K M.Monotonic and cyclic liquefaction of very loose sands with high silt content[J].Journal of Geotechnical and Geoenvironmental Engineering,2001,127(4):314-324.
[15]TERZAGHI K,PECK R B.Soil Mechanics in engineering practice(3rd edition)[M].New York:John Wiley&Sons Inc.,1996.
[16]谢定义.饱和砂土体液化的若干问题[J].岩土工程学报,1992,14(3):90-98.XIE Ding-yi.Some problems of liquefaction of the saturated sand[J].Chinese Journal of Geotechnical Engineering,1992,14(3):90-98.
[17]ZHANG Hui-ming,GARGA V K,ZENG Qiao-ling.Steady state strength of sand:concepts and experiment[J].Chinese Journal of Geotechnical Engineering,1999,21(2):230-235.张惠明,GARGA V K,曾巧玲.Steady state strength of sand:concepts and experiment[J].岩土工程学报,1999,21(2):230-235.
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