地震荷载作用下天津软土变形特性研究
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摘要
本文以天津滨海新区饱和软粘土为研究对象,按照Seed的转化方法将地震荷载转化为等效循环荷载,通过GDS动三轴系统对其进行单向激振循环荷载试验。文章主要研究了振动频率、循环应力比、固结围压等因素对地震荷载作用下滨海新区饱和软粘土动强度和变形特性的影响,并得出了一些对工程实践有意义的结论。
1.试验表明饱和软粘土存在着临界循环应力比,当循环应力比小于临界值时很难发生破坏,当大于临界值时在很少的循环振次内就达到了破坏。随着循环振动次数的增加,软土的累积变形逐渐增大,动强度则逐渐降低。
2.在地震荷载的作用下,滨海新区饱和软粘土的强度急剧下降,其内摩擦角仅为原来的35%左右;对原状土和加固土的对比研究表明,软土地基经过加固处理后,其动强度和承载力都得到了较大的提高。
3.对试验数据进行分析拟合,提出了基于试验基础的适合于滨海新区软粘土的动孔压计算模型。
4.根据试验结果,提出了滨海新区饱和软粘土在地震荷载作用下的动承载力计算公式和沉降变形计算公式。文中重点研究了软土的变形特性,并结合一震陷实例进行了对比分析。通过计算结果和实测数据的对比分析表明,计算值和实测值吻合的较好。
最后,本文对研究的工作进行了总结,并指出了尚未研究的课题或者研究中存在的一些问题,为进一步研究提供一定的理论依据和参考作用。
The saturated soft clays in the Binhai New Area is studied in this paper, and by the method of Seed the seismic loading is converted into the equivalent cyclic loading, and the effect of the vibration frequency, cyclic stress ratio and consolidation pressure on the dynamic strength and deformation characteristics of the soft clay under the seismic loading is studied based on the unidirectional cyclic loading test in the use of the GDS dynamic triaxial system, then some important conclusions are obtained.
1. The study shows that there is a critical cyclic stress ratio in the saturated soft clays. When the cyclic stress ratio is less than the critical value, it is difficult for the soft clay to break, or else it is easy to break in a few cycles. With the increase in the number of cycle of vibration, the cumulative deformation increases, while the strength reduces gradually.
2. Under the action of seismic loading, the strength of saturated soft clay in Binhai New Area decreased sharply and its internal friction angle was only about 35% of the original angle. By studying on undisturbed soil and reinforced soil, the results show that the dynamic strength and bearing capacity of soft foundation have been greatly improved after the soft clay reinforced.
3. Through analyzing the experimental data, a dynamic pore pressure calculation model that was suitable for the saturated soft clay in Binhai New Area was proposed in the paper.
4. Based on the test results, a formula for calculating cyclic carrying capacity and settlement deformation of the saturated soft clay in Binhai New Area was proposed under the seismic loading. The deformation characteristics of soft clay were focused on, and then a project of seismic subsidence was taken for example. By comparing the calculations with measured data, the result showed that the calculated value matched the actual value well.
In the end, the research work was summed up in the paper and some issues on the research were pointed out, which would provide a theoretical basis and reference for further research.
1.试验表明饱和软粘土存在着临界循环应力比,当循环应力比小于临界值时很难发生破坏,当大于临界值时在很少的循环振次内就达到了破坏。随着循环振动次数的增加,软土的累积变形逐渐增大,动强度则逐渐降低。
2.在地震荷载的作用下,滨海新区饱和软粘土的强度急剧下降,其内摩擦角仅为原来的35%左右;对原状土和加固土的对比研究表明,软土地基经过加固处理后,其动强度和承载力都得到了较大的提高。
3.对试验数据进行分析拟合,提出了基于试验基础的适合于滨海新区软粘土的动孔压计算模型。
4.根据试验结果,提出了滨海新区饱和软粘土在地震荷载作用下的动承载力计算公式和沉降变形计算公式。文中重点研究了软土的变形特性,并结合一震陷实例进行了对比分析。通过计算结果和实测数据的对比分析表明,计算值和实测值吻合的较好。
最后,本文对研究的工作进行了总结,并指出了尚未研究的课题或者研究中存在的一些问题,为进一步研究提供一定的理论依据和参考作用。
The saturated soft clays in the Binhai New Area is studied in this paper, and by the method of Seed the seismic loading is converted into the equivalent cyclic loading, and the effect of the vibration frequency, cyclic stress ratio and consolidation pressure on the dynamic strength and deformation characteristics of the soft clay under the seismic loading is studied based on the unidirectional cyclic loading test in the use of the GDS dynamic triaxial system, then some important conclusions are obtained.
1. The study shows that there is a critical cyclic stress ratio in the saturated soft clays. When the cyclic stress ratio is less than the critical value, it is difficult for the soft clay to break, or else it is easy to break in a few cycles. With the increase in the number of cycle of vibration, the cumulative deformation increases, while the strength reduces gradually.
2. Under the action of seismic loading, the strength of saturated soft clay in Binhai New Area decreased sharply and its internal friction angle was only about 35% of the original angle. By studying on undisturbed soil and reinforced soil, the results show that the dynamic strength and bearing capacity of soft foundation have been greatly improved after the soft clay reinforced.
3. Through analyzing the experimental data, a dynamic pore pressure calculation model that was suitable for the saturated soft clay in Binhai New Area was proposed in the paper.
4. Based on the test results, a formula for calculating cyclic carrying capacity and settlement deformation of the saturated soft clay in Binhai New Area was proposed under the seismic loading. The deformation characteristics of soft clay were focused on, and then a project of seismic subsidence was taken for example. By comparing the calculations with measured data, the result showed that the calculated value matched the actual value well.
In the end, the research work was summed up in the paper and some issues on the research were pointed out, which would provide a theoretical basis and reference for further research.
引文
[1]丁金伟,刘海笑,胡黎明.天津软粘土的动三轴试验研究.第七届全国土动力学学术会议论文集,北京:清华大学出版社,2006: 3~6
[2]刘振纹,秦崇仁,王建华等.循环荷载作用下软粘土的累积变形特性的研究[J].水利水电技术,2004,Vol.35
[3] Seed H B,Idriss I M. A simplified procedure for evaluating soil liquefaction potential[J]. Soil Mechanics and Foundations Division,ASCE,1981, (SM9): 1249~1273
[4] Seed H B,Chan C K. Effect of duration of stress application on soil deformation under repeated loading[A]. Proceedings5th international Congress on Soil Mechanics and Foundations.Vol.1[C].Pairs: Dunod,1961: 341~345
[5] Wilson N E,Elaohary M M. Consolidation of soils under cyclic loading [J]. Canadian Geot J,1974,2: 420~423
[6] Baligh M M,Levadoux J N. Consolidation theory for cyclic loading [J]. Journal of the Geotech-Nical Engineering Division,1980,106(5): 499~529
[7] Larew H G,Leonards G A. Repeated Load Strength Criterion. Proc.Highway Res.Board.1962,41,529
[8] O’REILLY M P. Cyclic Loading Testing of Soils[C]. Blackie and Son Ltd. Cyclic Loading of Soils: from Theory to Design. London:Blackie and Son Ltd,1991,70~121
[9]汤连生,张庆华,尹敬泽等.交通荷载下路基土动应力应变累积的特性[J].中山大学学报,2007,Vol.46(6)
[10]王军.单、双向激振循环荷载作用下饱和软粘土动力特性研究,博士学位论文,浙江大学,2007.
[11]黄茂松,李进军,李兴照等.饱和软粘土的不排水循环累积变形特性[J].岩土工程学报,2006,Vol.28(7)
[12]袁晓铭,孟上九,孙锐等.随机地震荷载下黏性土残余应变的半经验计算公式[J].水利学报,2004: 62~67
[13] G.R.Martin,W.D.Lian,H.B.Seed. Fundamentals of Liquefaction under Cyclic Loading[J]. Journal of the Geotechnical Engineering division,ASCE,Vol.101,1975
[14] Finn W.D.L.,Bhatia S.K. Prediction of seismic pore water pressure [A]. Proc.10th ICSMFE[C],1981.
[15] Yasuhara K. Post-cyclic undrained strength for cohesive soils[J]. Journal of Geotechnical Engineering,ASCE,1994,120(11): 1961~1979
[16]周建.循环荷载作用下饱和软粘土的孔压模型[J].工程勘察,2000: 7~9
[17]曾庆军,周波,龚晓南等.冲击荷载下饱和黏土孔压增长与消散规律[J].岩石力学与工程学报,2001,20(1): 1137~1141
[18]孟庆山,汪稔,陈震.淤泥质软土在冲击荷载作用下孔压增长模式[J].岩土力学,2004,25(7): 1017~1022
[19]唐益群,张曦,赵书凯等.地铁振动荷载下隧道周围饱和软黏土的孔压发展模型[J].土木工程学报,2007,40(4): 83~86
[20]顾中华.循环荷载作用下偏压固结饱和粘土孔压模型[J].地下空间与工程学报,2007,3(4): 776~780
[21]王兰民,张振中,王峻等.随机地震荷载作用下黄土动强度的试验方法[J].西北地震学报,1991,13(3): 50~55
[22]王洪瑾,沈瑞福,马奇国等.双向振动下土的动强度[J].清华大学学报,1996,36(4): 93~98
[23]叶银灿,来向华.杭州湾粉质土动强度特性研究[J].海洋科学,2003,27(2): 56~58
[24]张茹,费文平,马亢.饱和粘性土的动强度试验研究,中国科技论文在线: http://www.paper.edu.cn
[25]蒋军,陈龙珠.长期循环荷载作用下粘土的一维沉降[J].岩土工程学报,2001,23(3): 366~369
[26] Thiers G R. Cyclic stress-strain characteristics of clay[J]. Journal of Soil Mechanics and Foundations Division,ASCE,1968,94: 555~569
[27]朱延春.土的动强度分析[J].水电自动化与大坝监测,1991,42~46
[28] Duncan J M,Chang C Y. Nonlinear analysis of stress-strain in soils[J].Proc. ASCE,1970,96(SMS): 1629~1653
[29] Roscoe K H,Schofield A N,Wroth C P. On the yielding of soils[J]. Geotechnique,1958,8(1): 22~53
[30] Roscoe K H,Schofield A N,Thurairajah A. Yielding of clays in states wetter than critical[J]. Geotchnique,1963,13(3): 211~240
[31] Lade P,Duncan J M. Elastoplastic stress-strain response: cohesive soils[J]. Proc.ASCE JGED,1975,101(10): 1037~1053
[32] Dafalias Y F,HERRMANN L R. A bounding surface soil plasticity model [A]. Proc. Int. Symp. Soi1 under Cyclic and Transient loading[C]. Swansea,1980.
[33]沈珠江.土的三重屈服面应力应变模型[J].固体力学学报,1984,(2): 51~57
[34]龚晓南.粘土结构性对其力学性质的影响及形成原因分析[J].水利学报,2000,(10): 43~47
[35]谢定义.考虑土结构性的本构关系[J].土木工程学报,2000,33(4): 35~41
[36] Thiers G.R.,Seed H.B. Strength and Stress-stain characteristics of Clays Subjected to Seismic Loading Condition Vibration Effects of Earthquake On Soil and Foundation[J]. ASTM,1969.
[37]谢君斐,石兆吉.原状饱和黏土动力性能的试验研究[R].中国科学院工程力学研究所.地震工程研究报告(第三集).北京:地震出版社,1977.
[38]石兆吉,郁寿松,翁鹿年.塘沽新港地区震陷计算分析[[J].土木工程学报,1988,(4): 24~33
[39]刘汉龙.土体地震永久变形分析[D].南京:河海大学博士学位论文,1994.
[40]曾国熙等.地基处理手册,北京:中国建筑工业出版社,1988: 582~583
[41] Lee K L. Cyclic strength of a sensitive clay of eastern Canada[J]. Canadian Geotechnical Journal,1979,16(1): 163~176
[42] Yasuhara K,Yamanouchi T,Hirao K. Cyclic strength and deformation of normally consolidated clay[J]. Soils and Foundations,1982,22(3): 77~91
[43] Hardin,Drnevich. Shear modulus and damping in soils: measurement and parameter effects[J]. Journal of the soil mechanics and Foundation division,ASCE,1972,98(SM6): 603~624
[44]柳伟.各向异性固结饱和软粘土动力特性研究,硕士学位论文,浙江大学,2007.
[45] Matsui T , Ohara H and Ito T. Cyclic Stress-Strain History and Shear Characteristic of Clays[J]. Journal of Geotechnical Engineering,ASCE,1980,106(10): 1101~1120
[46]汪闻韶.土的动力强度和液化特性,北京:中国电力出版社,1997: 88~90
[47]谢定义.土动力学,西安:西安交通大学出版社,1988.
[48]石原研而.土质动力学基础,日本:鹿岛出版社,1982.
[49] Shamsher Prakash. Soil Dynamics,1981.
[50]冈本舜三.耐震工学,株式会社,1971.
[51]梅英宝,朱向荣,吕凡任.交通荷载作用下道路与软土地基弹塑性变形分析[J].浙江大学学报,2005,39(7): 998~1002
[52]刘明,黄茂松,李进军.地铁荷载作用下饱和软粘土的长期沉降分析[J].地下空间与工程学报,2006,2(5): 813~817
[53] Laerw H.G.,Leonards G.A.. Strength criterion for repeated loads[J]. HRBPore,1962,(41): 529~556
[54] Monismith C L, Ogawa N, Freeme C R. Permanent deformation characteristics of subgrade soils due to repeated loading[J]. Transp. Res. Rec. No. 537.Transportation Research Board. Washington D.C.,1975: 1~17
[55]刘惠珊,张在明.地震区的场地与地基基础.北京:中国建筑工业出版社,1994.
[2]刘振纹,秦崇仁,王建华等.循环荷载作用下软粘土的累积变形特性的研究[J].水利水电技术,2004,Vol.35
[3] Seed H B,Idriss I M. A simplified procedure for evaluating soil liquefaction potential[J]. Soil Mechanics and Foundations Division,ASCE,1981, (SM9): 1249~1273
[4] Seed H B,Chan C K. Effect of duration of stress application on soil deformation under repeated loading[A]. Proceedings5th international Congress on Soil Mechanics and Foundations.Vol.1[C].Pairs: Dunod,1961: 341~345
[5] Wilson N E,Elaohary M M. Consolidation of soils under cyclic loading [J]. Canadian Geot J,1974,2: 420~423
[6] Baligh M M,Levadoux J N. Consolidation theory for cyclic loading [J]. Journal of the Geotech-Nical Engineering Division,1980,106(5): 499~529
[7] Larew H G,Leonards G A. Repeated Load Strength Criterion. Proc.Highway Res.Board.1962,41,529
[8] O’REILLY M P. Cyclic Loading Testing of Soils[C]. Blackie and Son Ltd. Cyclic Loading of Soils: from Theory to Design. London:Blackie and Son Ltd,1991,70~121
[9]汤连生,张庆华,尹敬泽等.交通荷载下路基土动应力应变累积的特性[J].中山大学学报,2007,Vol.46(6)
[10]王军.单、双向激振循环荷载作用下饱和软粘土动力特性研究,博士学位论文,浙江大学,2007.
[11]黄茂松,李进军,李兴照等.饱和软粘土的不排水循环累积变形特性[J].岩土工程学报,2006,Vol.28(7)
[12]袁晓铭,孟上九,孙锐等.随机地震荷载下黏性土残余应变的半经验计算公式[J].水利学报,2004: 62~67
[13] G.R.Martin,W.D.Lian,H.B.Seed. Fundamentals of Liquefaction under Cyclic Loading[J]. Journal of the Geotechnical Engineering division,ASCE,Vol.101,1975
[14] Finn W.D.L.,Bhatia S.K. Prediction of seismic pore water pressure [A]. Proc.10th ICSMFE[C],1981.
[15] Yasuhara K. Post-cyclic undrained strength for cohesive soils[J]. Journal of Geotechnical Engineering,ASCE,1994,120(11): 1961~1979
[16]周建.循环荷载作用下饱和软粘土的孔压模型[J].工程勘察,2000: 7~9
[17]曾庆军,周波,龚晓南等.冲击荷载下饱和黏土孔压增长与消散规律[J].岩石力学与工程学报,2001,20(1): 1137~1141
[18]孟庆山,汪稔,陈震.淤泥质软土在冲击荷载作用下孔压增长模式[J].岩土力学,2004,25(7): 1017~1022
[19]唐益群,张曦,赵书凯等.地铁振动荷载下隧道周围饱和软黏土的孔压发展模型[J].土木工程学报,2007,40(4): 83~86
[20]顾中华.循环荷载作用下偏压固结饱和粘土孔压模型[J].地下空间与工程学报,2007,3(4): 776~780
[21]王兰民,张振中,王峻等.随机地震荷载作用下黄土动强度的试验方法[J].西北地震学报,1991,13(3): 50~55
[22]王洪瑾,沈瑞福,马奇国等.双向振动下土的动强度[J].清华大学学报,1996,36(4): 93~98
[23]叶银灿,来向华.杭州湾粉质土动强度特性研究[J].海洋科学,2003,27(2): 56~58
[24]张茹,费文平,马亢.饱和粘性土的动强度试验研究,中国科技论文在线: http://www.paper.edu.cn
[25]蒋军,陈龙珠.长期循环荷载作用下粘土的一维沉降[J].岩土工程学报,2001,23(3): 366~369
[26] Thiers G R. Cyclic stress-strain characteristics of clay[J]. Journal of Soil Mechanics and Foundations Division,ASCE,1968,94: 555~569
[27]朱延春.土的动强度分析[J].水电自动化与大坝监测,1991,42~46
[28] Duncan J M,Chang C Y. Nonlinear analysis of stress-strain in soils[J].Proc. ASCE,1970,96(SMS): 1629~1653
[29] Roscoe K H,Schofield A N,Wroth C P. On the yielding of soils[J]. Geotechnique,1958,8(1): 22~53
[30] Roscoe K H,Schofield A N,Thurairajah A. Yielding of clays in states wetter than critical[J]. Geotchnique,1963,13(3): 211~240
[31] Lade P,Duncan J M. Elastoplastic stress-strain response: cohesive soils[J]. Proc.ASCE JGED,1975,101(10): 1037~1053
[32] Dafalias Y F,HERRMANN L R. A bounding surface soil plasticity model [A]. Proc. Int. Symp. Soi1 under Cyclic and Transient loading[C]. Swansea,1980.
[33]沈珠江.土的三重屈服面应力应变模型[J].固体力学学报,1984,(2): 51~57
[34]龚晓南.粘土结构性对其力学性质的影响及形成原因分析[J].水利学报,2000,(10): 43~47
[35]谢定义.考虑土结构性的本构关系[J].土木工程学报,2000,33(4): 35~41
[36] Thiers G.R.,Seed H.B. Strength and Stress-stain characteristics of Clays Subjected to Seismic Loading Condition Vibration Effects of Earthquake On Soil and Foundation[J]. ASTM,1969.
[37]谢君斐,石兆吉.原状饱和黏土动力性能的试验研究[R].中国科学院工程力学研究所.地震工程研究报告(第三集).北京:地震出版社,1977.
[38]石兆吉,郁寿松,翁鹿年.塘沽新港地区震陷计算分析[[J].土木工程学报,1988,(4): 24~33
[39]刘汉龙.土体地震永久变形分析[D].南京:河海大学博士学位论文,1994.
[40]曾国熙等.地基处理手册,北京:中国建筑工业出版社,1988: 582~583
[41] Lee K L. Cyclic strength of a sensitive clay of eastern Canada[J]. Canadian Geotechnical Journal,1979,16(1): 163~176
[42] Yasuhara K,Yamanouchi T,Hirao K. Cyclic strength and deformation of normally consolidated clay[J]. Soils and Foundations,1982,22(3): 77~91
[43] Hardin,Drnevich. Shear modulus and damping in soils: measurement and parameter effects[J]. Journal of the soil mechanics and Foundation division,ASCE,1972,98(SM6): 603~624
[44]柳伟.各向异性固结饱和软粘土动力特性研究,硕士学位论文,浙江大学,2007.
[45] Matsui T , Ohara H and Ito T. Cyclic Stress-Strain History and Shear Characteristic of Clays[J]. Journal of Geotechnical Engineering,ASCE,1980,106(10): 1101~1120
[46]汪闻韶.土的动力强度和液化特性,北京:中国电力出版社,1997: 88~90
[47]谢定义.土动力学,西安:西安交通大学出版社,1988.
[48]石原研而.土质动力学基础,日本:鹿岛出版社,1982.
[49] Shamsher Prakash. Soil Dynamics,1981.
[50]冈本舜三.耐震工学,株式会社,1971.
[51]梅英宝,朱向荣,吕凡任.交通荷载作用下道路与软土地基弹塑性变形分析[J].浙江大学学报,2005,39(7): 998~1002
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