液化场地浅埋钢筋混凝土结构物变形及动土压力分析
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摘要
基于多重剪切机构塑性模型和液化前缘面的有效应力分析方法,分析不同地震强度下液化场地中浅埋大断面矩形钢筋混凝土结构物变形与地震动土压力分布特征,进而探索0.85g输入地震波条件下结构物与液化土间的相对位移差、结构物侧壁和顶底板土体的动土压力、剪切应力、有效应力和超孔隙水压力的变化规律。研究得出结构物的最大变形、弯矩和曲率值随着地震强度的加大而增大,结构物最先发生屈服变形部位位于拐角处,并逐步向周围扩展;场地发生液化模型中的结构物–液化土相互作用系数数值小于场地未发生液化模型,结构物与土体间的相对位移差值随着场地液化而剧增到一定值;作用于结构物侧壁的动土压力最大值和震后值随地震强度加大而增加,但不是简单的线性增长;结构物侧壁动土压力随着振动持续而增长,而作用于顶底板土层的剪切应力和侧壁有效应力随着土体液化而剧减。研究结论可为液化场地浅埋结构物的抗震设计提供可靠的依据和参考。
Based on the method of effective stress analysis using a multiple shear plasticity model and the concept of liquefaction front,numerical modeling for deformations and dynamic earth pressures acting on the shallow duct-type reinforced concrete(RC) structures subjected to earthquake motions is presented. Moreover,the change rules of the relative displacement between the underground structures and liquefiable soils,dynamic earth pressures acting on the sidewall of RC structures,shear stress and excess pore water pressures in liquefiable soil during earthquake for the cases with a crest input motion of 0.85 g are further investigated. The results indicate that the values of deformations and bending moments,curvatures of RC structures increase with the level of input motions. And plastic yield area firstly occurs on the corners of structure and expands to other areas. The interaction factors in liquefied models with strong motions are less than those of non-liquefied models with a motion of 0.1 g. The values of relative displacement between ground and structure increase sharply up to a stable value after the soil is liquefied during earthquakes. The maximum and residual values of dynamic earth pressures acting on sidewalls increase with shaking. However,the growth is not a simple linear relationship with the input motion. Onthe contrary,the shear stresses acting on the top and the bottom slab,and the horizontal effective stresses acting on sidewall decrease sharply when the soil is liquefied. These results provide the foundation and references for the seismic design of shallow underground structures in the liquefiable soils.
Based on the method of effective stress analysis using a multiple shear plasticity model and the concept of liquefaction front,numerical modeling for deformations and dynamic earth pressures acting on the shallow duct-type reinforced concrete(RC) structures subjected to earthquake motions is presented. Moreover,the change rules of the relative displacement between the underground structures and liquefiable soils,dynamic earth pressures acting on the sidewall of RC structures,shear stress and excess pore water pressures in liquefiable soil during earthquake for the cases with a crest input motion of 0.85 g are further investigated. The results indicate that the values of deformations and bending moments,curvatures of RC structures increase with the level of input motions. And plastic yield area firstly occurs on the corners of structure and expands to other areas. The interaction factors in liquefied models with strong motions are less than those of non-liquefied models with a motion of 0.1 g. The values of relative displacement between ground and structure increase sharply up to a stable value after the soil is liquefied during earthquakes. The maximum and residual values of dynamic earth pressures acting on sidewalls increase with shaking. However,the growth is not a simple linear relationship with the input motion. Onthe contrary,the shear stresses acting on the top and the bottom slab,and the horizontal effective stresses acting on sidewall decrease sharply when the soil is liquefied. These results provide the foundation and references for the seismic design of shallow underground structures in the liquefiable soils.
引文
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[16]刘汉龙,井合进,一井康二.大型沉箱式码头岸壁地震反应分析[J].岩土工程学报,1998,20(2):26–30.(LIU Hanlong,IAI S,ICHII K.Seismic response analysis of large-size caisson quay wall[J].Chinese Journal of Geotechnical Engineering,1998,20(2):26–30.(in Chinese))
[2]汪明武,金菊良,李丽.基于实码加速遗传算法的投影寻踪方法在砂土液化势可视化评价中的应用[J].岩石力学与工程学报,2004,23(4):631–634.(WANG Mingwu,JIN Juliang,LI Li.Application of PP method based on RAGA to assessment of sand liquefaction potential[J].Chinese Journal of Rock Mechanics and Engineering,2004,23(4):631–634.(in Chinese))
[3]高广运,顾中华,杨宏明.循环荷载下饱和黏土不排水强度计算方法[J].岩土力学,2004,25(增2):379–382.(GAO Guangyun,GU Zhonghua,YANG Hongming.A calculation method for undrained strength of saturated clay under cyclic loads[J].Rock and Soil Mechanics,2004,25(Supp.2):379–382.(in Chinese))
[4]KRAUTHAMMER T,CHEN Y.Soil-structure interface effects on dynamics interaction analysis of reinforced concrete lifelines[J].Soil Dynamics and Earthquake Engineering,1989,8(1):32–42.
[5]WANG M W,IAI S,TOBITA T.Effective stress analysis of underground RC structures during earthquakes[J].Annuals of Disaster Prevention Research Institute,Kyoto University,2005,48(B):371–381.
[6]WANG M W,IAI S,TOBITA T.Seismic performances of underground RC structures in liquefiable soils in nuclear plants[C]//PORBAHA A,SHEN S,WARTMAN J,et al ed.Ground Modification and Seismic Mitigation.Reston,VA:ASCE/GEO Institute,2006:387–394.
[7]汪明武,IAI S.地下RC结构物地震响应特征土工离心试验的模拟[J].地震工程与工程振动,2007,27(3):150–155.(WANG Mingwu,IAI S.Numerical simulation of centrifuge modeling for seismic responses of underground RC structures[J].Journal ofEarthquake Engineering and Engineering Vibration,2007,27(3):150–155.(in Chinese))
[8]周健,董鹏,池永.软土地下结构的地震土压力分析研究[J].岩土力学,2004,25(4):554–559.(ZHOU Jian,DONG Peng,CHI Yong.Research on seismic soil pressure of underground structures in soft soils[J].Rock and Soil Mechanics,2004,25(4):554–559.(in Chinese))
[9]姜忻良,宋丽梅.软土地层中地下隧道结构地震反应分析[J].地震工程与工程振动,1999,19(1):65–68.(JIANG Xinliang,SONG Limei.Seismic response analysis of underground tunnel in soft soil[J].Journal of Earthquake Engineering and Engineering Vibration,1999,19(1):65–68.(in Chinese))
[10]刘华北,宋二祥.可液化土中地铁结构的地震液化响应[J].岩土力学,2005,26(3):381–386.(LIU Huabei,SONG Erxiang.Earthquake induced liquefaction response of subway structure in liquefiable soil[J].Rock and Soil Mechanics,2005,26(3):381–386.(in Chinese))
[11]严松宏,梁波,高波.地下结构纵向抗震动力可靠度分析[J].岩石力学与工程学报,2005,24(1):71–76.(YAN Songhong,LIANG Bo,GAO Bo.Dynamic analysis of longitudinal aseismic reliability of underground Structures[J].Chinese Journal of Rock Mechanics and Engineering,2005,24(1):71–76.(in Chinese))
[12]严松宏,高峰,高波,等.沉管隧道地震反应分析若干问题的研究[J].岩石力学与工程学报,2004,23(5):846–850.(YAN Songhong,GAO Feng,GAO Bo,et al.Studies on some issues of seismic responses analysis for submerged tunnel[J].Chinese Journal of Rock Mechanics and Engineering,2004,23(5):846–850.(in Chinese))
[13]IAI S,MATSUNAGA Y,KAMEOKA T.Strain space plasticity model for cyclic mobility[J].Soils and Foundations,1992,32(2):1–15.
[14]IAI S,MATSUNAGA Y,KAMEOKA T.Parameter identification for a cyclic mobility model[J].Report of Port and Harbour Research Institute,1990,29(4):57–83.
[15]汪明武,井合进,飞田哲男.栈桥式构筑物抗震性能动态离心模型试验的数值模拟[J].岩土工程学报,2005,27(7):738–741.(WANG Mingwu,IAI S,TOBITA T.Numerical modeling for dynamic centrifuge model test of the seismic behaviors of pile-supported structure[J].Chinese Journal of Geotechnical Engineering,2005,27(7):738–741.(in Chinese))
[16]刘汉龙,井合进,一井康二.大型沉箱式码头岸壁地震反应分析[J].岩土工程学报,1998,20(2):26–30.(LIU Hanlong,IAI S,ICHII K.Seismic response analysis of large-size caisson quay wall[J].Chinese Journal of Geotechnical Engineering,1998,20(2):26–30.(in Chinese))
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