摘要
为解决我国铁路线路不可避免地穿越风积沙河谷地区遇到的地基液化问题,通过振动台试验探究了碎石桩加固风积沙地层的液化规律及频响特征。研究结果表明,在EL Centro地震波作用下:(1)碎石桩能有效抵抗风积沙地基沉降,大幅度增强其抗液化能力,尤其是地基中部(3/5桩长),并且能将液化易发部位从中部转移到浅层,有利于对液化场地采取加固措施;(2)碎石桩充当优良的排水路径,能弱化桩间土的剪胀剪缩循环活动性,使孔压保持稳态增长;(3)通过相关性分析发现,当地震烈度过高时,碎石桩的排水效果会达到极限,地基深处的部分孔隙水将从桩间土渗流至地表,导致路径上孔压增长的相互影响性显著增强;(4)碎石桩加固后的风积沙地基在低频段(0~10 Hz)的响应集中且最为强烈,在高频域(25~30 Hz)的响应具有高程放大效应,而液化的地层会弱化地基原有的能量传递效果;(5)通过希尔波特谱可知,随着地震波从下往上传播,碎石桩地基的响应主频段会向高频(≥22 Hz)扩展与迁移,而发生液化的土层具有高频过滤作用。
In order to solve the problem of foundation liquefaction encountered in railway linesunavoidably crossing aeolian sand valleys,the liquefaction law and frequency response characteristics of gravel piles reinforced aeolian sand strata are explored through a shaking table.The results of the study show that under the action of the EL Centro seismic wave:(1)Reinforced aeolian sand foundation with gravel pile can effectively resists surface settlement and greatly enhances its liquefaction resistance,especially in the middle of the foundation(3/5 pile length).And it can transfer the liquefied prone parts from the middle to the shallow layer,which is conducive to the reinforcement measures for the liquefaction site.(2)The gravel pile acts as an excellent drainage path,which can weaken the cyclic activity of the soil between the piles,so that the pore pressure can maintain a steady increase.(3)Through the correlation analysis,it is found that when the earthquake intensity is too high,the drainage effect of the gravel pile will reach the limit.Therefore,part of the pore water deep in the foundation will seep from the soil between the piles to the surface,resulting in significant increase in the mutual influence of pore pressure growth along the path.(4)Under the action of EL Centro seismic wave,the response of the aeolian sand foundation reinforced with gravel piles is concentrated and most intense in the low frequency range(0~10 Hz),and the response in the high-frequency domain(25~30 Hz)has an elevation amplification effect.The liquefied formation will weaken the original energy transfer effect of the foundation.(5)According to the Hillport spectrum,as the EI Centro seismic wave propagates from the bottom to the top,the main response frequency band of the gravel pile foundation will expand and migrate to the high frequency(≥22 Hz).The research results can provide reference for the design of anti-liquefaction and seismic strength of aeolian sand formations.
作者
周垣
吴红刚
朱兆荣
马至刚
孙浩
冯康
ZHOU Yuan;WU Honggang;ZHU Zhaorong;MA Zhigang;SUN Hao;FENG Kang(School of Civil Engineering and Architecture,Southwest University of Science and Technology,Mianyang 621010,China;Northwest Research Institute Co.,Ltd of CREC,Lanzhou 730070,China)
出处
《铁道标准设计》
北大核心
2024年第4期78-87,共10页
Railway Standard Design
基金
国家重点研发计划项目(2018YFC1504903)
甘肃省自然科学基金项目(145RJZA068)。
关键词
碎石桩
风积沙地基
振动台
EL
Centro地震波
液化规律
频响特征
gravel pile
aeolian sand foundation
shaking table
El Centro seismic wave
liquefaction law
frequency response characteristics
