汶川地震路堤成灾模式及土工格栅加筋变形控制研究
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摘要
为研究路基工程的抗震设计问题,首先对汶川8.0级地震震区路基震害进行调查,发现强震作用下绝大多数未加筋路堤为浅表层边坡坍塌破坏,极少数路堤发生半幅路面错落的本体滑坡现象,所有路堤均未出现沿基础界面的滑动,而土工格栅加筋路堤震害程度轻微得多。根据变形破坏模式,提出以侧向变形控制为核心的土工格栅布筋方案,即在路堤顶部满铺土工格栅、中上部铺设短格栅。利用未加筋路堤和土工格栅加筋路堤大型振动台模型试验进行加筋变形控制方案有效性的对比研究。试验结果表明,路堤顶部满铺土工格栅,阻断竖向裂缝的扩展,从而抑制路堤本体滑坡;护坡道上方铺设短格栅,可有效抑制路堤侧向变形及边坡坍塌。通过对加速度、动土压力测量结果的对比分析,发现土工格栅加筋后,路堤模型的自振频率提高12%,0.7倍坡高处加速度放大系数在中震下减小27%,在大震下减小41%,动土压力幅值也会大幅减小。
To study the seismic design of subgrade engineering,subgrade seismic damage of Wenchuan Ms8.0 earthquake was investigated.It was found that most of the un-reinforced embankment suffered from shallow collapse of slope,of which a few were damaged by the sliding of embankment body,but neither of the embankment slid along the embankment-foundation interface.the damage level of geogrid-reinforced embankment was much slighter than that of un-reinforced embankment.Based on the investigation,the geogrid layout scheme was proposed to control the lateral deformation of embankment with long geogrid laid on the top of the embankment,and short geogrid laid on the upper part of the embankment.To validate this layout scheme,the un-reinforced and reinforced embankment were studied comparatively with large-scale shaking table model tests.Results showed that fissure spreading downward was restrained by long geogrid on the top of the embankment,thus deep slide prevented.Lateral deformation and shallow slide of the slope were restrained by short geogrid on the upper part of the embankment.By comparative analysis of acceleration and dynamic earth pressure between those two types of model test,it was found that when the road embankment was reinforced,natural frequency would increase by 12%,magnification factor of acceleration at 0.7 times the height of embankment would decrease by 27% under medium earthquake,decrease by 41% under large earthquake,and dynamic earth pressure would decrease largely also.
To study the seismic design of subgrade engineering,subgrade seismic damage of Wenchuan Ms8.0 earthquake was investigated.It was found that most of the un-reinforced embankment suffered from shallow collapse of slope,of which a few were damaged by the sliding of embankment body,but neither of the embankment slid along the embankment-foundation interface.the damage level of geogrid-reinforced embankment was much slighter than that of un-reinforced embankment.Based on the investigation,the geogrid layout scheme was proposed to control the lateral deformation of embankment with long geogrid laid on the top of the embankment,and short geogrid laid on the upper part of the embankment.To validate this layout scheme,the un-reinforced and reinforced embankment were studied comparatively with large-scale shaking table model tests.Results showed that fissure spreading downward was restrained by long geogrid on the top of the embankment,thus deep slide prevented.Lateral deformation and shallow slide of the slope were restrained by short geogrid on the upper part of the embankment.By comparative analysis of acceleration and dynamic earth pressure between those two types of model test,it was found that when the road embankment was reinforced,natural frequency would increase by 12%,magnification factor of acceleration at 0.7 times the height of embankment would decrease by 27% under medium earthquake,decrease by 41% under large earthquake,and dynamic earth pressure would decrease largely also.
引文
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[2]TATSUOKA F,TATEYAMA M,MOHRI Y,et al.Remedial treatment of soil structures using geosynthetic-reinforcing technology[J].Geotextiles and Geomembranes,2007,25(4/5):204-220.
[3]周朝晖.2008年四川汶川8.0级地震强震动台网观测记录[J].四川地震,2008,(4):25-29.(ZHOU Zhaohui.The strong ground motion recordings of the Ms8.0Wenchuan earthquake in Sichuan province[J].Earthquake Research in Sichuan,2008,(4):25-29.(in Chinese))
[4]LIN M L,WANG K L.Seismic slope behavior in a large-scale shaking table model test[J].Engineering Geology,2006,86(2/3):118-133.
[5]PRASAD S K.TOWHATA I.Shaking table tests in earthquake geotechnical engineering[J].Current Science,2004,87(10):1398-1404.
[6]WEGNER J L.Dynamic wave-soil-structure interaction analysis in thetime domain[J].Computers and Structures,2005,83(27):2206-2214.
[7]MEYMAND P J.Shaking table scale model tests of nonlinear soil-pile-superstructure interaction in soft clay[Ph.D.Thesis][D].Berkeley:University of California,1998.
[8]徐光兴,姚令侃,高召宁.边坡动力特性与动力响应的大型振动台模型试验研究[J].岩石力学与工程学报,2008,28(3):624-632.(XU Guangxing,YAO Lingkan,GAO Zhaoning.Large-scale shaking table model tests on dynamic characteristics and dynamic responses of slope[J].Chinese Journal of Rock Mechanics and Engineering,2008,28(3):624-632.(in Chinese))
[9]徐光兴,姚令侃,李朝红,等.边坡地震动力响应规律及地震动参数影响研究[J].岩土工程学报,2008,30(6):918-923.(XU Guangxing,YAO Lingkan,LI Zhaohong,et al.Study of the dynamic responses of slope under earthquake and the influence of ground motion parameters on the responses[J].Chinese Journal of Geotechnical Engineering,2008,30(6):918-923.(in Chinese))
[10]刘小生,王钟宁,赵剑明,等.面板堆石坝振动模型试验及动力分析研究[J].水利学报,2002,(2):29-35.(LIU Xiaosheng,WANG Zhongning,ZHAO Jianming,et al.Advancement of technology on shaking table model test and dynamic analysis of CFRD[J].Journal of Hydraulic Engineering,2002,(2):29-35.(in Chinese))
[11]凌贤长,郭明珠,王东升,等.液化场地桩基桥梁震害响应大型振动台模型试验研究[J].岩土力学,2006,27(1):7-10,22.(LING Xianzhang,GUO Mingzhu,WANG Dongsheng,et al.Large-scale shaking table model test of seismic response of bridge of pile foundation in ground of liquefaction[J].Rock and Soil Mechanics,2006,27(1):7-10,22.(in Chinese))
[12]陈国兴,庄海洋,杜修力,等.土-地铁隧道动力相互作用的大型振动台试验——试验结果分析[J].地震工程与工程振动,2007,27(1):164-170.(CHEN Guoxing,ZHUANG Haiyang,DU Xiuli,et al.A large-scale shaking table test for dynamic soil-metro tunnel interaction:analysis of test results[J].Journal of Earthquake Engineering and Engineering Vibration,2007,27(1):164-170.(in Chinese))
[13]武思宇,宋二祥,刘华北,等.刚性桩复合地基的振动台试验研究[J].岩土工程学报,2005,27(11):1334-1337.(WU Siyu,SONG Erxiang,LIU Huabei,et al.Shaking table test of composite foundation with rigid pile[J].Chinese Journal of Geotechnical Engineering,2005,27(11):1334-1337.(in Chinese))
[14]ELEMAM M M,BATHURST R J,HATAMI K.Numerical modeling of reinforced soil retaining walls subjected to base acceleration[C]//the13th WCEE.Vancouver:[s.n.],2004:2621.
[15]EL-EMAM M M,BATHURST R J.In uence of reinforcement parameters on the seismic response of reduced-scale reinforced soil retaining walls[J].Geotextiles and Geomembranes,2007,25(1):33-49.
[16]郑颖人,陈祖煜,王恭先,等.边坡与滑坡工程治理[M].北京:人民交通出版社,2007.(ZHENG Yingren,CHEN Zuyu,WANG Gongxian,et al.Engineering treatment of slope and landslide[M].Beijing:China Communications Press,2007.(in Chinese))
[17]中华人民共和国国家标准编写组.GB50111-2006铁路工程抗震设计规范[S].北京:中国计划出版社,2006.(The National Standards Compilation Group of People′s Republic of China.GB50111-2006Code for seismic design of railway[S].Beijing:China Planning Press,2006.(in Chinese))
[18]中华人民共和国行业标准编写组.JTJ004-89公路工程抗震设计规范[S].北京:人民交通出版社,1999.(The Professional Standards Compilation Group of People′s Republic of China.JTJ004-89Code for seismic design of highway[S].Beijing:China Communications Press,1999.(in Chinese))
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