标题 | 基于Ansys的滑坡抗滑桩动力特性的有限元分析 |
范文 | 於文欢等 摘要:采用Ansys有限元计算软件,以某滑坡体为例,建立了有限元的三维模型,并选取Kobe地震波中的代表性波段,研究了在地震作用下抗滑桩的侧面应力、动土压力以及桩身的弯矩分布规律。结果表明:在地震作用下,抗滑桩侧面受到不可忽略的侧面应力,对其抗震能力产生有利影响;地震时,抗滑桩产生的弯矩呈现“凸”形,在滑坡带部位达到最大;同时还出现负弯矩,对抗滑桩的抗震不利,在设计时应加以考虑。 关键词:Ansys;地震作用;边坡稳定;抗滑桩;动力响应;侧面应力;有限元 中图分类号:TU435 文献标志码:A 文章编号: 16721683(2014)05005404 Finite element analysis of dynamic characteristics of antislide pile based on Ansys YU Wenhuan1,2,YAO Tianbao1,REN Jianmin1 (1.School of Civil Engineering,Lanzhou Jiaotong University,Lanzhou 730070,China; 2.Key Laboratory of Road & Bridge and Underground Engineering of Gansu Province,Lanzhou 730070,China) Abstract:The finite element calculation software Ansys was used to develop a threedimensional model of a landslide.The representative range of Kobe earthquake wave was selected to investigate the distribution characteristics of lateral stress,soil pressure,and bending moment of the antislide pile.The results showed that the lateral stress of the antislide pile is significant under earthquakes,which may have a favorable impact on the antiseismic performance of the pile;the bending moment of the antislide pile shows in the “convex” shape and it reaches the maximum in the landslide area during the earthquake;and the occurrence of negative moment can have an adverse impact on the antiseismic performance of the pile. Key words:Ansys;earthquake;slope stability;antislide pile;dynamic response;lateral stress;finite element 地震是边坡及其抗滑结构失稳破坏的重要诱发因素。我国是一个多地震国家,各类建筑工程的工程地质条件复杂,强烈地震往往在山区丘陵地区的城镇居住区、道路、水工构筑物等区域产生大量崩塌、滑坡等次生灾害,给国家和人民的生命财产造成了巨大损失[12]。 抗滑桩是国内外普遍采用的滑坡支挡结构措施[3]。对于地震荷载下抗滑桩和边坡之间相互作用机理、抗滑桩后土压力分布形式和抗滑桩支护边坡在地震作用下的稳定性等问题,已有不少研究:叶海林等[4]、雷文杰等[5]通过大型振动台试验研究了地震荷载作用下边坡抗滑桩的抗震性能,于玉贞等[6]利用土工离心机及专用振动台进行了砂土边坡的动力离心模型试验,为研究抗滑桩的抗震机制提供了一定参考,罗瑜等[7]、雷庆兰等[8]、 任自铭[9]采用数值模拟分析了抗滑桩在地震作用下的动力响应。但是,以上研究均是采用的二维模型,没有考虑抗滑桩的侧面与边坡的相互作用,不能真实反映抗滑桩的内力分布。因此本文作者将建立抗滑桩边坡的三维有限元模型,考虑了抗滑桩的侧面与边坡的相互作用,研究地震作用下抗滑桩加固边坡动力响应,揭示地震历程中桩身不同位置的侧面应力、轴向应变以及弯矩变化规律,为地震作用下抗滑桩的设计提供参考。 1 计算模型及参数选取 1.1 计算模型的建立 某一碎石土滑坡的高度为54 m,长度为109 m,滑带倾角为27°,滑带厚度为1 m,抗滑桩截面为2 m×2 m的矩形,桩的高度为19.2 m,在滑床埋深为11.7 m,根据文献[10],将抗滑桩设在滑坡中部,以取得最好的抗震效果,其三维有限元模型见图1。考虑到计算精度和计算效率,整个模型共划分形成了10 765个节点,5 320 个单元。滑坡体及抗滑桩的材料参数见表1。 岩土体的本构关系采用理想弹塑性模型;屈服准则采用广泛应用于岩土类材料的DruckerPrager屈服准则;抗滑桩 由图5可知,各个位置处的轴向应变时程变化规律基本相同,随着地震加速度的增大轴向应变也增大,且也表现出明显的滞后性。抗滑桩顶部的N1位置的应变很小,几乎不产生弯矩,这是因为随桩身高度增加,所受的滑坡土体推力减弱,弯矩变化规律类似于悬臂梁的悬臂部分受到不均匀荷载产生的弯矩变化。位于滑坡带内的N2应变突然变大,抗滑桩上半部分受到了由于地震产生的较大滑坡土体推力,使抗滑桩N2附近受弯严重,应变和弯矩较大。桩底位置N3的应变较N2位置要小,嵌固于稳定基岩内,且锚固深度较深,几乎相当于悬臂梁的固定端,即使桩底受到较大的滑坡土体推力,其应变与弯矩也不会太大。震后悬臂抗滑桩桩身应变随高度的变化规律见图 6。 由此可见,在地震荷载作用下,抗滑桩的弯矩分布呈显“凸”形,且随着地震荷载的不断变化,其所受弯矩有时可能 为负弯矩,因此在设计抗滑桩的时应予以充分考虑,防止抗滑桩远离山一侧的钢筋配置过少,造成抗滑桩拉裂。 3 结论 (1)在地震作用下,抗滑桩反复振动,侧面将由于桩的滑动而与土体进行摩擦,产生较大的侧面应力。侧面应力沿桩高方向不均匀分布,在桩顶位置比较大,随着深度逐渐地减小,但在底部也达到5.1%。现行抗滑桩的设计规范或者按照平面应变问题进行的建模计算由于没有考虑这一因素,造成设计偏保守。故在设计中应根据情况,在预留一定的安全富裕系数后,适当地加以考虑,达到经济合理。 (2)不同高度处的侧面应力、轴向应变以及弯矩分布规律基本相同,都是随着地震加速度的增大而增大,但其峰值出现时间均要晚于加速度峰值出现时间,表现出一定的滞后性,可见土体对桩的变形有阻滞作用。 (3)悬臂抗滑桩的嵌固端与悬臂部分分界面随着地震波的输入应变急剧增大,悬臂部分随着高度增加而应变减小,反映了悬臂抗滑桩弯矩的“凸”形分布规律。随着地震荷载的不断变化,其所受弯矩有时可能为负弯矩,因此在设计抗滑桩时应予以考虑,防止混凝土被拉裂。 参考文献(References): [1] 佟恩宠,施耀新,曾圣福.唐山大地震天津市工程震害[M].天津:天津科学技术出版社,1984.(TONG Enchong,SHI Yaoxin,ZENG Shengfu.The tangshan earthquake of tianjin engineering earthquake damage[M].Tianjin:tianjin science and technology press,1984.(in Chinese)) [2] 罗永红.地震作用下复杂斜坡响应规律研究[D].成都:成都理工大学,2011.(LUO Yonghong.Study on complex slopes response law under earthquake action[D].Chengdu:Chengdu University of Technology,2011.(in Chinese)) [3] 汪鹏程,朱大勇,许强.强震作用下加固边坡的动力响应及不同加固方式的比较研究[J].合肥工业大学学报:自然科学版,2009,32(10):15011509.(WANG Pengcheng,ZHU Dayong,XU Qiang.Dynamic response of slopes subjected to intense earthquakes and effect comparison between various support modes[J].Journal of HeFei University of Technology:natural science edition.2009,32 (10):15011509.(in Chinese)) [4] 叶海林,郑颖人,李安洪,等.地震作用下边坡抗滑桩振动台试验研究[J].岩土工程学报,2012,34(2):251257.(YE Hailin,ZHENG Yingren,LI Anhong,et al.Shaking table tests on stabilizing piles of slopes under earthquakes[J].Chinese Journal of geotechnical engineering.2012,34 (2):251257.(in Chinese)) [5] 雷文杰,郑颖人,王恭先,等.沉埋桩加固滑坡体模型试验的机制分析[J]. 岩石力学与工程学报,2007,26(7):13471355.(LEI Wenjie,ZHANG Yingren,WANG Gongxian,et al. 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Xinzheng,JIANG Jianjing.ANSYS Solid65 element analysis of concrete structures under complicated stress condition[J].Building Structure,2003,(6):2224.(in Chinese)) [12] 陈波,吕西林,李培振,等.用ANSYS模拟结构地基动力相互作用振动台试验的建模方法[J].地震工程与工程振动,2002,22(1):126131.(CHEN Bo,LV Xilin,LI Peizhen,et al.Modeling of dynamic solistructure interaction by ansys program[J].Earthquake engineering and Engineering vibration,2002,22 (1):126131.(in Chinese)) [13] 郑颖人,赵尚毅.用有限元强度折减法求边(滑)坡支挡结构的内力[J].岩石力学与工程学报,2004,23(20):35523558.(ZHENG Yingren,ZHAO Shangyi.Calculation of inner force of support structure for landslide /slope by using strength reduction FEM[J].Chinese Journal of Rock Mechanics and Engineering,2004,23(20):35523558.(in Chinese)) [14] 曾攀.有限元分析及应用[M].北京:清华大学出版社,2004.(ZENG pan.Finite element analysis andapplication[M].Beijing:Tsinghua University press,2004.(in Chinese)) [15] 姚爱军,史高平,梅超.悬臂抗滑桩加固边坡地震动力响应模型试验研究[J].岩土力学,2012,33(2):5358.(YAO Aijun,SHI Gaoping,MEI Chao.Experimental model study of seismic response of slope reinforced by cantilever stabilizing piles[J].Rock and Soil Mechanics Rock and Soil Mechanics,2012,33(2):5358.(in Chinese)) [9] 雷庆兰,龚照森.强震下抗滑桩加固边坡土体的稳定机制及动力响应探讨[J].西华大学学报:自然科学版,2013,32(6):104108.(LEI Qinglan,GONG Zhaosen.Study on the stability mechanism and dynamic response of antislide pile reinforing soil slope under a strong earthquake[J].Journal of Xihua University:natural science edition,2013,32 (6):104108.(in Chinese)) [10] 雷文杰,郑颖人,冯夏庭.滑坡治理中抗滑桩桩位分析[J].岩土工程学报,2006,27(6):950954.(LEI Wenjie,ZHENG Yingren,Analysis of pile location on landslide control[J].Chinese Journal of geotechnical engineering,2006,27 (6):950954.(in Chinese)) [11] 陆新征,江见鲸.利用ANSYS Solid65单元分析复杂应力条件下的混凝土结构[J].建筑结构,2003,(6);2224.(LU Xinzheng,JIANG Jianjing.ANSYS Solid65 element analysis of concrete structures under complicated stress condition[J].Building Structure,2003,(6):2224.(in Chinese)) [12] 陈波,吕西林,李培振,等.用ANSYS模拟结构地基动力相互作用振动台试验的建模方法[J].地震工程与工程振动,2002,22(1):126131.(CHEN Bo,LV Xilin,LI Peizhen,et al.Modeling of dynamic solistructure interaction by ansys program[J].Earthquake engineering and Engineering vibration,2002,22 (1):126131.(in Chinese)) [13] 郑颖人,赵尚毅.用有限元强度折减法求边(滑)坡支挡结构的内力[J].岩石力学与工程学报,2004,23(20):35523558.(ZHENG Yingren,ZHAO Shangyi.Calculation of inner force of support structure for landslide /slope by using strength reduction FEM[J].Chinese Journal of Rock Mechanics and Engineering,2004,23(20):35523558.(in Chinese)) [14] 曾攀.有限元分析及应用[M].北京:清华大学出版社,2004.(ZENG pan.Finite element analysis andapplication[M].Beijing:Tsinghua University press,2004.(in Chinese)) [15] 姚爱军,史高平,梅超.悬臂抗滑桩加固边坡地震动力响应模型试验研究[J].岩土力学,2012,33(2):5358.(YAO Aijun,SHI Gaoping,MEI Chao.Experimental model study of seismic response of slope reinforced by cantilever stabilizing piles[J].Rock and Soil Mechanics Rock and Soil Mechanics,2012,33(2):5358.(in Chinese)) |
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