基于CPTU孔压消散试验的欠固结土OCR计算方法  

OCR evaluation method of underconsolidated soil through CPTU pore pressure dissipation test

作　　者：居俊[1] 刘松玉[1] 刘志彬[1] 蔡国军[1] 周伯明 

机构地区：[1]东南大学岩土工程研究所,南京210096 [2]江苏省崇启大桥建设现场指挥部,启东226255

出　　处：《东南大学学报（自然科学版）》2011年第3期642-646,共5页Journal of Southeast University：Natural Science Edition

基　　金：国家自然科学基金资助项目(40702047);江苏省交通厅资助项目(09Y33)

摘　　要：利用CPTU孔压消散试验数据对欠固结土的欠固结状态进行定量评价,并在此基础上提出基于固结状态参数的欠固结土超固结比计算方法.结合现场CPTU孔压消散试验及室内固结试验对崇启大桥北接线工程沿线③1层软土应力历史进行了研究.结果表明:消散时间足够长时,CPTU孔压消散实验曲线的末端无限逼近原位初始孔压,且消散曲线尾端的实测孔压与时间平方根倒数成线性相关性,提出采用时间平方根倒数外推法计算原位初始孔压.当所计算的原位初始孔压大于静水压力时,则判定软土处于欠固结状态,进而建议采用固结状态参数对软土的欠固结程度进行定量评价,固结状态参数越小,说明欠固结程度越高.根据CPTU孔压消散试验计算了沿线软土③1层(淤泥质粉质黏土)的欠固结程度,然后利用室内固结试验成果验证了其合理性.基于OCR传统计算公式中系数与固结状态参数间定量关系,提出了考虑固结程度的欠固结土OCR计算公式.Underconsolidated state of soft soil is quantitatively evaluated through in situ CPTU（cone penetration test with pore pressure measurement） pore pressure dissipation test,and then the overconsolidation ratio（OCR） calculation method of underconsolidated soil based on the parameter of consolidation state is researched.The stress history of soft soil at ③1 layer along the northern expressway connection project of Chongqi Bridge is studied according to the in situ CPTU pore pressure dissipation test and laboratory oedometer test.The results indicate that the end part of the CPTU pore pressure dissipation curve will approximate to the in situ initial pore pressure when dissipation time is long enough.And the measured pore pressure of the end part of dissipation curve is found to be linearly correlated to corresponding inverse square root of time.A calculation method is put forward in this paper to calculate the in situ initial pore pressure through extrapolation of inverse square root of time.The soft soil can be considered as underconsolidated if the in situ initial pore pressure is higher than hydrostatic pressure.Furthermore,the parameter of consolidation state is suggested to evaluate the degree of underconsolidation.The smaller the parameter of consolidation state is,the higher the degree of underconsolidation will be.The underconsolidation degree of ③1 layer along the expressway is first determined through CPTU pore pressure dissipation test,and then the reasonability of this evaluation method is verified by laboratory test results.On the basis of quantitative relationship analysis of the coefficient in the traditional OCR formula and the parameter of consolidation,an OCR calculation formula which can consider the consolidation degree of underconsolidated soil is presented.

关 键 词：孔压静力触探 孔压消散试验 超固结比 固结状态参数 欠固结土 

分 类 号：TU413[建筑科学—岩土工程]