初始剪应力对饱和粉土液化特性影响试验研究
|
摘要
为探寻饱和粉土的液化特性,利用GDS空心圆柱仪进行了一系列循环扭剪试验。在初始剪应力τs和循环剪应力τcy共同作用下,试样的最小剪应力τmin=τs-τcy存在3种类型:τmin<0,τmin=0和τmin>0。试验结果表明:当τmin≤0时,试样的孔压可以达到有效围压,其破坏模式为循环液化;当τmin>0时,试样的孔压始终达不到有效围压,其破坏模式为过大的累计应变。饱和粉土的循环强度随着初始剪应力τs与初始有效平均主应力0p′之比值SSR(初始剪应力比)的增加呈现出先减小后增大变化趋势,且SSR=0.1~0.15时的循环强度最低。当SSR≤0.1时,孔压比的发展模式随着循环剪应力比的增加由"快—平稳—急剧"的增长模式向"快—平稳"的增长模式转变;当SSR>0.1时,孔压比的发展呈现"快—平稳"的增长模式。
In order to investigate the role which the initial static shear stress plays in the liquefaction of saturated silt, a series of cyclic torsional shear tests are conducted. Three types of cyclic loading patterns, stress reversal, intermediate and stress no-reversal, are employed by varying the initial static shear level τs and the cyclic shear stress amplitude τcy. The observed failure state types of the samples can be distinguished into the cyclic liquefaction and the excessive accumulated permanent deformation according to whether the pore pressure of the samples reaches the effective confining one. The test results show that under the low initial static shear level, an increase in the ratio SSR of the initial static shear stress τs to the initial effective mean confining stress 0p′ leads to a decrease in the cyclic shear strength. However, under the higher initial static shear level, an increase in SSR increases the cyclic shear strength. It is found that the growth mode of the pore pressure ratio depends on the combination of the initial and cyclic shear stresses. When SSR≤0.1, with the increase of τcy, the growth mode of the pore pressure ratio changes from a state of "fast–steady-sharp" to a state of "fast–steady". On the other hand, the growth mode of the pore pressure ratio is in a state of "fast–steady" when SSR>0.1.
In order to investigate the role which the initial static shear stress plays in the liquefaction of saturated silt, a series of cyclic torsional shear tests are conducted. Three types of cyclic loading patterns, stress reversal, intermediate and stress no-reversal, are employed by varying the initial static shear level τs and the cyclic shear stress amplitude τcy. The observed failure state types of the samples can be distinguished into the cyclic liquefaction and the excessive accumulated permanent deformation according to whether the pore pressure of the samples reaches the effective confining one. The test results show that under the low initial static shear level, an increase in the ratio SSR of the initial static shear stress τs to the initial effective mean confining stress 0p′ leads to a decrease in the cyclic shear strength. However, under the higher initial static shear level, an increase in SSR increases the cyclic shear strength. It is found that the growth mode of the pore pressure ratio depends on the combination of the initial and cyclic shear stresses. When SSR≤0.1, with the increase of τcy, the growth mode of the pore pressure ratio changes from a state of "fast–steady-sharp" to a state of "fast–steady". On the other hand, the growth mode of the pore pressure ratio is in a state of "fast–steady" when SSR>0.1.
引文
[1]YOSHIMI,Y,OH-OKA,H.Influence of degree of shear stress reversal on the liquefaction potential of saturated sand[J].Soils and Foundations,1975,15(3):27–40.
[2]SEED H B.Earthquake-resistant design of earth dams[C]//Proceedings of the Symposium on Seismic Design of Earth Damsand Caverns.New York,1983:41–64.
[3]VAID Y P,CHERN J C.Cyclic and monotonic undrained response of saturated sands[C]//Advances in the Art of Testing Soils Under Cyclic Conditions.ASCE,1985:120–147.
[4]SEED R B,HARDER L F.SPT-based analysis of cyclic pore pressure generation and undrained residual strength[C]//Proceedings of H.B.Seed Memorial Symposium.California:University of California Berkeley,1990:351–376.
[5]YANG J,SZE H Y.Cyclic behaviour and resistance of saturated sand under non-symmetrical loading conditions[J].Géotechnique,2011,61(1):59–73.
[6]SIVATHAYALAN S,HA D.Effect of initial static shear stress on the cyclic resistance of sands in simple shear loading[J].Canadian Geotechnical Journal,2011,48(10):1471–1484.
[7]CHIARO G,KOSEKI J,SATO T.Effects of initial static shear on liquefaction and large deformation properties of loose saturated Toyoura sand in undrained cyclic torsional shear tests[J].Soils and Foundations,2012,52(3):498–510.
[8]王余庆,栾芳,韩清宇,等.预测轻亚粘土液化势的统计公式[J].岩土工程学报,1980,2(3):103–112.(WANG Yu-qing,LUAN Fang,HAN Qing-ya,et al.Explorations of liquefaction problems of satnrated sands[J].Journal of Geotechnical Engineering,1980,2(3):103–112.(in Chinese))
[9]石兆吉,郁寿松,王余庆,等.饱和轻亚黏土地基液化可能性判别[J].地震工程与工程振动,1984,4(3):71–82.(SHI Zhao-ji,YU Shou-song,WANG Yu-qin,et al.Prediction of liquefaction potential of saturated clayey silt[J].Earthquake Engineering and Engineering Vibration,1984,4(3):71–82.(in Chinese))
[10]刘恢先.唐山大地震震害(第一册)[M].北京:地震出版社,1989.(LIU Hui-xian.The Tangshan Great Earthquake in1976[M].Beijing:Earthquake Press,1989.(in Chinese))
[11]GBJ11—89建筑抗震设计规范[S].1989.(GBJ11-89 Code for seismic design of buildings[S].1989.(in Chinese))
[12]HYDE A F,HIGUCHI T,YASUHARA K.Liquefaction,cyclic mobility,and failure of silt[J].Journal of Geotechnical and Geoenvironmental Engineering,2006,132(6):716–735.
[13]沈扬,张朋举,闫俊,等.主应力轴旋转下小偏压固结密实粉土崩塌特性及孔压模型研究[J].岩土力学,2012,33(9):2561–2568.(SHEN Yang,ZHANG Peng-ju,YAN Jun,et al.Collapse characteristics and unified pore water pressure model of slightly anisotropically consolidated dense silt under principal stress axis rotation[J].Rock and Soil Mechanics,2012,33(9):2561–2568.(in Chinese))
[14]SA?LAM S,BAKIR B S.Cyclic response of saturated silts[J].Soil Dynamics and Earthquake Engineering,2014,61:164–175.
[15]HYODO M,MURATA H,YASUFUKU N,et al.Undrained cyclic shear strength and residual shear strain of saturated sand by cyclic triaxial tests[J].Soils and Foundations,1991,31(3):60–76.
[16]牛建新,汪闻绍.循环扭剪试验中饱和砂土的某些动力特性[J].水利学报,1994(5):77–83.(NIU Jian-xin,WANG Wen-shao.Some dynamic properties of saturated sands with torsional shear apparatus[J].Journal of Hydraulic Engineering,1994(5):77–83.(in Chinese))
[17]王炳辉,陈国兴.循环荷载下饱和南京细砂的孔压增量模型[J].岩土工程学报,2011,33(2):188–194.(WANG Bing-hui,CHEN Guo-xing.A pore water pressure increment model for saturated nanjing fine sand subjected to cyclic loading[J].Chinese Journal of Geotechnical Engineering,2011,33(2):188–194.(in Chinese))
[2]SEED H B.Earthquake-resistant design of earth dams[C]//Proceedings of the Symposium on Seismic Design of Earth Damsand Caverns.New York,1983:41–64.
[3]VAID Y P,CHERN J C.Cyclic and monotonic undrained response of saturated sands[C]//Advances in the Art of Testing Soils Under Cyclic Conditions.ASCE,1985:120–147.
[4]SEED R B,HARDER L F.SPT-based analysis of cyclic pore pressure generation and undrained residual strength[C]//Proceedings of H.B.Seed Memorial Symposium.California:University of California Berkeley,1990:351–376.
[5]YANG J,SZE H Y.Cyclic behaviour and resistance of saturated sand under non-symmetrical loading conditions[J].Géotechnique,2011,61(1):59–73.
[6]SIVATHAYALAN S,HA D.Effect of initial static shear stress on the cyclic resistance of sands in simple shear loading[J].Canadian Geotechnical Journal,2011,48(10):1471–1484.
[7]CHIARO G,KOSEKI J,SATO T.Effects of initial static shear on liquefaction and large deformation properties of loose saturated Toyoura sand in undrained cyclic torsional shear tests[J].Soils and Foundations,2012,52(3):498–510.
[8]王余庆,栾芳,韩清宇,等.预测轻亚粘土液化势的统计公式[J].岩土工程学报,1980,2(3):103–112.(WANG Yu-qing,LUAN Fang,HAN Qing-ya,et al.Explorations of liquefaction problems of satnrated sands[J].Journal of Geotechnical Engineering,1980,2(3):103–112.(in Chinese))
[9]石兆吉,郁寿松,王余庆,等.饱和轻亚黏土地基液化可能性判别[J].地震工程与工程振动,1984,4(3):71–82.(SHI Zhao-ji,YU Shou-song,WANG Yu-qin,et al.Prediction of liquefaction potential of saturated clayey silt[J].Earthquake Engineering and Engineering Vibration,1984,4(3):71–82.(in Chinese))
[10]刘恢先.唐山大地震震害(第一册)[M].北京:地震出版社,1989.(LIU Hui-xian.The Tangshan Great Earthquake in1976[M].Beijing:Earthquake Press,1989.(in Chinese))
[11]GBJ11—89建筑抗震设计规范[S].1989.(GBJ11-89 Code for seismic design of buildings[S].1989.(in Chinese))
[12]HYDE A F,HIGUCHI T,YASUHARA K.Liquefaction,cyclic mobility,and failure of silt[J].Journal of Geotechnical and Geoenvironmental Engineering,2006,132(6):716–735.
[13]沈扬,张朋举,闫俊,等.主应力轴旋转下小偏压固结密实粉土崩塌特性及孔压模型研究[J].岩土力学,2012,33(9):2561–2568.(SHEN Yang,ZHANG Peng-ju,YAN Jun,et al.Collapse characteristics and unified pore water pressure model of slightly anisotropically consolidated dense silt under principal stress axis rotation[J].Rock and Soil Mechanics,2012,33(9):2561–2568.(in Chinese))
[14]SA?LAM S,BAKIR B S.Cyclic response of saturated silts[J].Soil Dynamics and Earthquake Engineering,2014,61:164–175.
[15]HYODO M,MURATA H,YASUFUKU N,et al.Undrained cyclic shear strength and residual shear strain of saturated sand by cyclic triaxial tests[J].Soils and Foundations,1991,31(3):60–76.
[16]牛建新,汪闻绍.循环扭剪试验中饱和砂土的某些动力特性[J].水利学报,1994(5):77–83.(NIU Jian-xin,WANG Wen-shao.Some dynamic properties of saturated sands with torsional shear apparatus[J].Journal of Hydraulic Engineering,1994(5):77–83.(in Chinese))
[17]王炳辉,陈国兴.循环荷载下饱和南京细砂的孔压增量模型[J].岩土工程学报,2011,33(2):188–194.(WANG Bing-hui,CHEN Guo-xing.A pore water pressure increment model for saturated nanjing fine sand subjected to cyclic loading[J].Chinese Journal of Geotechnical Engineering,2011,33(2):188–194.(in Chinese))