CAJ | 학술논문

基于 u-p 有限元公式模拟饱和砂土中水和土颗粒完全耦合效应，建立液化侧向流场地群桩动力反应分析的三维数值模型。模型中，砂土采用多屈服面弹塑性本构模型模拟、黏土采用多屈服面运动塑性模型模拟，群桩在计算过程中保持线弹性状态；采用20节点的六面体单元和考虑孔压效应的20-8节点分别划分黏土层和饱和砂层；选用剪切梁边界处理计算域的人工边界，模拟地震过程中土层的剪切效应；应用瑞利阻尼考虑体系的阻尼效应。随后对比分析2×2群桩中各单桩的地震反应规律，结果表明，各单桩的弯矩、位移时程规律基本一致，峰值弯矩及峰值位移出现时刻滞后于输入加速度峰值时刻，上坡向桩的弯矩和位移峰值大于下坡向的桩的反应值。接着通过改变桩间距研究群桩效应，随着桩间距增加，群桩中各单桩的弯矩最大值均出现在土层分界处，且各单桩的弯矩、桩顶位移逐渐增大。最后给出液化侧向流场地群桩效应的基本原因，得出该类场地群桩抗震设计的基本认识。
기우 u-p 유한원공식모의포화사토중수화토과립완전우합효응，건립액화측향류장지군장동력반응분석적삼유수치모형。모형중，사토채용다굴복면탄소성본구모형모의、점토채용다굴복면운동소성모형모의，군장재계산과정중보지선탄성상태；채용20절점적륙면체단원화고필공압효응적20-8절점분별화분점토층화포화사층；선용전절량변계처리계산역적인공변계，모의지진과정중토층적전절효응；응용서리조니고필체계적조니효응。수후대비분석2×2군장중각단장적지진반응규률，결과표명，각단장적만구、위이시정규률기본일치，봉치만구급봉치위이출현시각체후우수입가속도봉치시각，상파향장적만구화위이봉치대우하파향적장적반응치。접착통과개변장간거연구군장효응，수착장간거증가，군장중각단장적만구최대치균출현재토층분계처，차각단장적만구、장정위이축점증대。최후급출액화측향류장지군장효응적기본원인，득출해류장지군장항진설계적기본인식。
The Finite Element method was used to analyze the dynamic response of pile groups in the ground subjected to the liquefaction-induced lateral flow of soils.The u-p Finite Element for-mulation was used to depict the coupling effect of water and sand soil particles in the Finite Ele-ment analysis.A 3D numerical model was developed to analyze the effect of a 2×2 pile group sub-jected to liquefaction-induced lateral spreading.In this model,sand was simulated using a pres-sure-independent multi-yield surface plastic model.Clay material served as a nonlinear hysteretic material with a multi-surface kinematic plasticity model,and the pile group maintained its linear behavior in the process of calculation.The clay layer and saturated sand layer were meshed in a 20-node brick element and separately in a 20-8 node element.The boundary of the numerical model was considered as the shear beam boundary,which simulated the shear effect of the soil layer dur-ing the earthquake.Finally,the Rayleigh damping method was used to model the damping of the system.The dynamic response of each pile in pile group was compared,and it showed that the bending moment and displacement time history of piles at different depths developed in the same way,and the time of maximum bending moment and displacement of the pile appears to lag be-hind the time of peak acceleration of the input seismic wave.The maximum bending moment and displacement of the leading pile were larger than the those of the back piles.By comparing the maximum bending moment and displacement,it can also be concluded that,as depth increases,the maximum bending moment first increases and then decreases.The bending moment of the pile at the 2.5 m depth was greater than those at other depths.In terms of displacement,as depth in-creased,the maximum pile displacement decreased,and the maximum displacement of the pile head was greater than other observed points on the pile.This demonstrated the different behaviors of the pile bending moment response.In order to consider the effect of pile spacing on the pile group effect,several Finite Element models were developed for different pile spacing.This model-ing concluded that the maximum bending moment appeared to occur in the boundary of different soil layers.As pile spacing increased,the maximum bending moment and pile head displacement in the group increased.In the pile group with pile spacing equal to 7D (diameter),the maximum bending moment of the each pile was very close.The difference was about 3% when pile spacing was equal to 5D ,and the difference was about 4%,when pile spacing was equal to 3D .The maxi-mum bending moment of the first pile group was 10% larger than the bending moment of the sec-ond pile group.In the last part of the study,the cause of the pile group effect was analyzed and a basic understanding of the seismic design requirements for this type of pile group was obtained.