地下结构碎石排水层抗液化措施数值试验
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摘要
通过数值模拟验证液化的隔振作用。在浅埋地下结构周围设置碎石排水层,应用FLAC3D作碎石排水层法抗液化数值模拟试验,分析不同碎石排水层方案的抗液化效果和液化场施加碎石排水层后地下结构的动力特性变化。计算结果表明,典型液化场中砂土达到液化状态,其加速度、速度、位移振幅马上衰减;砂土在液化状态变为流体,液化过程是砂土体积压应变不断积累增大的过程,液化后体积压应变积累不再增加,液化土有效应力和抗剪强度均为0,不能传递剪力,起隔离外界力的作用,液化场中结构的加速度反应也比非液化场或弹性场小。液化场中结构的存在降低了其周围的动水压力,结构阻障了周围土液化的产生。液化场中地下结构周围设置碎石排水层,结构周围则不会液化,远处液化场超静水压力显著降低,结构不出现上浮,结构下沉,水平漂移减小,内力增大。研究成果为地下结构穿越液化土层设计提供理论及试验基础。
The numerical simulation test is performed for validation vibration isolation function of liquefaction.A gravel drainage layer is applied around underground structure;the anti-liquefaction numerical simulation tests of gravel drainage layer were performed using FLAC3D.Anti-liquefaction effect of the different gravel drainage layer programmes is analyzed;and dynamic characteristic change of underground structures after imposition a gravel drainage layer in liquefaction field is also analyzed.Calculations indicate that when the sandy soil is in the liquefied condition in the model liquefaction field,its acceleration,the speed,the displacement oscillation amplitude weaken immediately.The sandy soil becomes the fluid in the liquefied condition.The liquefaction process is the process which the sandy soil volume pressure strain accumulates unceasingly.The volume pressure strain accumulation no longer increases after the sandy soil is liquefied.The effective stress of liquefied soil is zero.The shearing strength is zero.The liquefied soil cannot transmit the shearing force and isolates outside force.The acceleration of structure in liquefied field is also smaller than the non-liquefied field or the elastic field.The structure,which is in the liquefied field,reduced the hydrodynamic pressure around structure.The structure interrupted the liquefaction around structure.The gravel drainage layer around underground structure will not be liquefied.The ultra hydrostatic pressure in distant place liquefied field reduces obviously.The structure is not floating,the structure subsided.The horizontal drift reduced.The internal force increased.Research results will provide a theoretical and experimental basis for the design of underground structures through the liquefied soil layer.
The numerical simulation test is performed for validation vibration isolation function of liquefaction.A gravel drainage layer is applied around underground structure;the anti-liquefaction numerical simulation tests of gravel drainage layer were performed using FLAC3D.Anti-liquefaction effect of the different gravel drainage layer programmes is analyzed;and dynamic characteristic change of underground structures after imposition a gravel drainage layer in liquefaction field is also analyzed.Calculations indicate that when the sandy soil is in the liquefied condition in the model liquefaction field,its acceleration,the speed,the displacement oscillation amplitude weaken immediately.The sandy soil becomes the fluid in the liquefied condition.The liquefaction process is the process which the sandy soil volume pressure strain accumulates unceasingly.The volume pressure strain accumulation no longer increases after the sandy soil is liquefied.The effective stress of liquefied soil is zero.The shearing strength is zero.The liquefied soil cannot transmit the shearing force and isolates outside force.The acceleration of structure in liquefied field is also smaller than the non-liquefied field or the elastic field.The structure,which is in the liquefied field,reduced the hydrodynamic pressure around structure.The structure interrupted the liquefaction around structure.The gravel drainage layer around underground structure will not be liquefied.The ultra hydrostatic pressure in distant place liquefied field reduces obviously.The structure is not floating,the structure subsided.The horizontal drift reduced.The internal force increased.Research results will provide a theoretical and experimental basis for the design of underground structures through the liquefied soil layer.
引文
[1]陈国兴.岩土地震工程学[M].北京:科学出版社,2007.
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[3]MARTIN G R,FINN L W D,et al.Fundamentals ofliquefaction under cyclic loading[J].Journal of theGeotechnical Engineering Division,1975,5:423-438.
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[7]孙锐,袁晓铭.非均等固结下饱和砂土孔压增量简化计算公式[J].岩土工程学报,2005,27(9):1022-1025.SUN Rui,YUAN Xiao-min.Simplified incrementalformula for estimating pore water pressure of saturatedsands under anisotropic consolidation[J].ChineseJournal of Geotechnical Engineering,2005,27(9):1022-1025.
[8]孙锐,袁晓铭.循环荷载下液化对土层水平往返变形的影响[J].西北地震学报,2009,31(1):8-14.SUN Rui,YUAN Xiao-ming.Effect of liquefaction oncyclic deformation of soil layers[J].NorthwesternSeismological Journal,2009,31(1):8-14.
[9]刘光磊,宋二祥,刘华北.可液化地层中地铁隧道地震响应数值模拟及其试验验证[J].岩土工程学报,2007,29(12):1815-1822.LIU Guang-lei,SONG Er-xiang,LIU Hua-bei.Numericalmodeling of subway tunnels in liquefiable soil underearthquakes and verification by centrifuge tests[J].Chinese Journal of Geotechnical Engineering,2007,29(12):1815-1822.
[10]汪明武,李丽.浅埋矩形RC结构物地震液化上浮有效应力分析[J].振动工程学报,2008,21(3):286-290.WANG Ming-wu,LI Li.Effective stress analysis ofliquefaction-induced up lift of shallow duct-typeunderground RC structures[J].Journal of VibrationEngineering,2008,21(3):286-290.
[2]陈育民,徐鼎平.FLAC/FLAC3D基础与工程实例[M].北京:中国水利水电出版社,2009.
[3]MARTIN G R,FINN L W D,et al.Fundamentals ofliquefaction under cyclic loading[J].Journal of theGeotechnical Engineering Division,1975,5:423-438.
[4]BYRNE,PETER M.A cyclic shear-volume coupling andpore pressure model for sand[C]//Second InternationalConference on Recent Advances in GeotechnicalEarthquake Engineering and Soil Dynamics.Missouri:Louis,1991:47-55.
[5]郑永来,杨德林,李文艺,等.地下结构抗震[M].上海:同济大学出版社,2007.
[6]孙锐,袁晓铭.地震荷载下饱和砂土孔压增长时程计算方法[J].地震工程与工程振动,.2005,26(3):261-263.SUN Rui,YUAN Xiao-min.A method for ca lculatingtime-dependent pore water pressure rise of saturatedsands under earthquake loading[J].EarthquakeEngineering and Engineering Vibration,2005,26(3):261-263.
[7]孙锐,袁晓铭.非均等固结下饱和砂土孔压增量简化计算公式[J].岩土工程学报,2005,27(9):1022-1025.SUN Rui,YUAN Xiao-min.Simplified incrementalformula for estimating pore water pressure of saturatedsands under anisotropic consolidation[J].ChineseJournal of Geotechnical Engineering,2005,27(9):1022-1025.
[8]孙锐,袁晓铭.循环荷载下液化对土层水平往返变形的影响[J].西北地震学报,2009,31(1):8-14.SUN Rui,YUAN Xiao-ming.Effect of liquefaction oncyclic deformation of soil layers[J].NorthwesternSeismological Journal,2009,31(1):8-14.
[9]刘光磊,宋二祥,刘华北.可液化地层中地铁隧道地震响应数值模拟及其试验验证[J].岩土工程学报,2007,29(12):1815-1822.LIU Guang-lei,SONG Er-xiang,LIU Hua-bei.Numericalmodeling of subway tunnels in liquefiable soil underearthquakes and verification by centrifuge tests[J].Chinese Journal of Geotechnical Engineering,2007,29(12):1815-1822.
[10]汪明武,李丽.浅埋矩形RC结构物地震液化上浮有效应力分析[J].振动工程学报,2008,21(3):286-290.WANG Ming-wu,LI Li.Effective stress analysis ofliquefaction-induced up lift of shallow duct-typeunderground RC structures[J].Journal of VibrationEngineering,2008,21(3):286-290.
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