基于CPTU的海相黏土固结状态和灵敏度估算方法

由于用传统的方法(室内试验和原位试验)确定海相黏土的固结状态及灵敏度有较大误差,基于CPTU孔压消散曲线的末端无限逼近原位初始孔压且末端实测孔压与时间的倒数近似呈线性关系的特点,采用时间倒数外推法计算原位初始孔压,通过比较原位初始孔压和静水压力的大小,对海相黏土的固结状态进行定量分析和评价。现场试验结果表明,采用时间倒数外推法可以快速判断海相黏土的固结状态。采用固结状态参数对该土的欠固结程度进行定量评价,固结状态参数越小,欠固结程度越高。利用CPTU的锥尖阻力和侧摩阻力(剔除由夹层产生的异常参数)对海相黏土的灵敏度进行估算,并与原位十字板剪切试验的结果进行对比。结果表明:原位十字板剪切试验易受夹层的影响,灵敏度偏低;CPTU试验确定的灵敏度能判断出夹层所在位置,计算结果更加灵敏,因此可用CPTU估算海相黏土的灵敏度。

An estimation method of consolidation state and sensitivity for marine clayey soil based on piezocone penetration test

As traditional methods(laboratory tests and in situ tests) cause large errors in estimation of the consolidation state and sensitivity for structural marine clayey soil,based on the characteristics that the end part of the CPTU pore pressure dissipation curve approximates the in situ initial pore pressure,and the measured pore pressure of the end part of the dissipation curve is found to be linearly correlated to the inverse of time,this paper puts forward a new method of extrapolating the inverse of time to calculate initial pore pressure.Through comparison of in situ initial pore pressure and hydrostatic pressure,quantitative analysis and assessment of the consolidation state of marine clayey soil was carried out.In situ test results show that,with the new method,it can be quickly judged whether the marine clayey soil is consolidated completely.The consolidation state parameter is used to evaluate the degree of underconsolidation of marine clayey soil;the smaller the consolidation state parameter is,the higher the degree of underconsolidation.Meanwhile,the cone resistance and side friction(rejecting the unusual parameter caused by the interlayer) measured by CPTU are employed to estimate the sensitivity of marine clayey soil.Comparison with thein situ test and CPTU shows that the result of the in situ test is readily influenced by the interlayer and its sensitivity is lower;the higher sensitivity based on CPTU can be used to judge the location of the interlayer.Hence,the method based on CPTU is proven to be suitable for estimating the sensitivity of marine clayey soil.