孔压静力触探在确定砂土内摩擦角中的应用

Application of PCPT Data to the Determination of Internal Friction Angle of Sandy Soil

内摩擦角作为砂土的抗剪强度指标之一,是工程设计的重要参数。常规海洋工程勘察中主要依据室内土工试验确定,如三轴压缩试验、直接剪切试验、颗粒粒径、级配和密实度等。随着孔压静力触探(Piezocone Penetration Test, PCPT)在海洋工程勘察中广泛开展,利用孔压静力触探测试的锥尖阻力、侧壁摩阻力和孔隙水压力等参数确定砂土内摩擦角具有无需取样、快速、合理、可靠的优点,在桩基础、管线路由、水下基础等海洋工程勘察中具有越来越重要的工程意义。本文总结了3种利用PCPT资料确定砂土内摩擦角的方法即Mayne提出的内摩擦角评估经验公式、砂土最大最小经验公式和Senneset等提出的计算砂土内摩擦角经验公式,在中国广东沿海某风电场开展了3个钻孔的应用实践。对结果进行对比分析后认为,在熟练掌握PCPT测试方法、资料采集、数据处理和成果解释的基础上,依据Senneset等提出的计算方法,用PCPT资料确定砂土内摩擦角,具有一定的可靠性与适用性。

As one of the shear strength indexes of sandy soil,the internal friction angle is an important parameter in engineering design,and in conventional marine engineering surveys it is mainly determined by indoor geotechnical tests such as triaxial compression test,direct shear test and particle size,gradation and compactness.With the broadly implementing of PCPT in marine engineering surveys,parameters such as cone resistance,sleeve friction and pore-water pressure measured through PCPT have been used to determine the internal friction angle of sandy soil,which has the advantages of no sampling,fast,reasonable and reliable and is of more and more important engineering significance in the marine engineering surveys such as pile foundation,pipeline routing and underwater foundations.In the present paper,three types of methods in which the PCPT data is used for determining the internal friction angle of sandy soil are summarized,which are the empirical formula for evaluating the internal friction angle proposed by Mayne,the maximum minimum experience formula for sandy soil and the empirical formula for calculating the internal friction angle of sandy soil proposed by Senneset,and application practice is carried out in three boreholes taken from a wind farm in Guangdong coastal area of China.It has been illustrated that using PCPT data to determine the internal friction angle of sandy soil has certain reliability and applicability if skilled in mea-suring method,data acquisition,data processing and interpretation of PCPT and based on the calculation method proposed by Senneset.