南海迭层土物理力学特性的研究

我国海域普遍分布有迭层土，由于结构的特殊性，对于其性质的准确把握，直接影响到海洋工程诸如打桩、钻井船插深等问题预测的准确性，关系到海洋工程建设的安全。现场进行孔压静力触探CPTU试验以及室内试验，分析我国南海海域迭层土的物理、力学性质的特点，对迭层土抗剪强度值的确定进行探讨。CPTU试验数据显示，迭层土的物理力学性质与单一土层具有较明显的差异；由于迭层土中砂层的存在，室内三轴不排水剪切试验（UU试验）确定的不排水强度明显偏低，是CPTU确定的不排水抗剪强度的下限值。CPTU的结果可以较好地反映了迭层土的特点，根据CPTU试验结果得到的摩阻比变化范围较大，在0～8之间远大于一般的砂土或黏土的变化范围，摩阻比与修正端阻之间的关系可用双曲线近似表示。建议进行静力分析时，迭层土不排水抗剪强度参数选取应参考CPTU试验结果。

Study of characteristics of laminated soil in South China Sea

Laminated soil distributes widely in the sea around China. Due to its special fabric, its physico-mechanical properties are different from the normal soil which will affect prediction of pile driving, spudcan penetration. In this paper, field piezocone penetration test(CPTU) and laboratory test methods are used to analyze the physico-mechanical properties of laminated soil in South China Sea; and the shear strength of laminated soil is discussed. The test results show that the physico-mechanical properties of laminated soil are different from normal sand’s or clay’s ones. Since the sand lamination presence, the undrained shear strength of laminated soil getting from UU tests is conservative; and it is the lower limit of that got from CPTU. The results of CPTU could show the special characteristics of laminated soil more clearly. The change scale of friction ratio of laminated soil got from CPTU is from 0 to 8 which is much larger than that of normal sand and clay. The relationship between friction ratio and corrected cone resistance could be simulated with hyperbola approximately. The special characteristics of laminated soil should be considered when the undrained shear strength is determined in static analysis properly.