桩基施工对边坡黏土强度影响试验研究  

Experimental study on influence of pile foundation construction on slope clay strength

作　　者：石月晴 游克勤 SHI Yueqing;YOU Keqin(School of Civil Engineering, Chongqing Jiaotong University, Chongqing 400074, China;School of Civil Engineering,Chongqing University,Chongqing 400045 , China)

机构地区：[1]重庆交通大学土木工程学院,重庆400074 [2]重庆大学土木工程学院,重庆400045

出　　处：《水利水运工程学报》2018年第2期97-103,共7页Hydro-Science and Engineering

基　　金：重庆市基础与前沿研究计划项目(cstc2015jcyi BX0139)

摘　　要：桩基施工过程中会产生持续较大的振动,引起土体累计变形和超静孔压增大,造成土体强度降低。以来福士广场西侧边坡为工程背景,研究黏土边坡在施工振动过程中的强度变化规律。使用测振仪和超低频传感器对现场抗滑桩的振动冲击进行测试,根据振动产生的动应力特征进行室内静、动三轴试验,模拟土单元体原位应力状态和应力路径,并提供试验方法,最后分析了土体强度在施工期间动应力作用下的折减。现场振动测试结果表明:地表出现的最大振动速度可达2 cm/s,且在离桩心26 m处仍然有0.16~0.24 cm/s的振动,同时随着桩基施工深度的增加,土体的振动作用增强。固结不排水条件下的静、动三轴试验结果表明:土体的动强度明显低于静强度,通过做不同围压下的总应力强度包线,测得土体的总强度指标C_(cu)=49.5 k Pa,φ_(cu)=17.0°,不同影响距离下桩基施工对土体强度的影响符合不同的试验规律。试验边坡黏土符合土体折减的经验曲线,考虑到振动力增大边坡下滑力和振动对土体强度的影响,其综合强度折减系数取0.7~0.8。The continuous large vibration will be generated during the construction of the pile,resulting in the cumulative deformation of soil and the increase of the excess pore pressure,which eventually leads to the decrease of soil strength.Taking the west side of Raffles Square as an engineering case history,studies of the law of the clay slope＇s strength variation in the process of construction vibration are carried out.The vibration and shock of the antislide piles were tested by using the vibration meter and the ultra-low frequency sensor,according to the dynamic stress characteristics of the vibration,the static and dynamic triaxial tests were carried out to simulate the in situ stress state and stress path of the soil unit,in addition a test method has been developed.At last the reduction of soil strength under the action of dynamic stress during construction was analyzed.The analysis results of field vibration tests show that the maximum vibration velocity of the surface is up to 2 cm/s,as well as there is still a vibration at 26 m distance away from the pile,of which the velocity is approximately 0.16-0.24 cm/s.At the same time,with the increase of pile foundation construction,the vibration effect of soil is enhanced.Except for the above findings,it is also found that in the consolidated undrain condition,the results of static and dynamic triaxial tests show that when the total stress intensity envelope under different confining pressures was made,the dynamic strength of the soil is obviously lower than that of the static strength.And the relevant indexes data from results are obtained,and the soil body total strength index C_（cu）= 49.5 kPa and φ_（cu）= 17.0° are measured.The influences of pile foundation construction on soil strength are different according to different experimental rules.The test slope is clay conforms to the experience curve of soil strength reduction.Considering that the influences of the vibration force will increase slope sliding force and affect the strength of the soil,the com

关 键 词：边坡桩基 黏土强度 应力组合 静动力试验 

分 类 号：TV64[水利工程—水利水电工程] TU45[建筑科学—岩土工程]