Practical Methods for Determining Soil Strength Parameters in Offshore Wind Power Geotechnical Investigation

  Introduction  In order to determine soil strength parameters more accurately and reliably, based on domestic and foreign engineering experience and research results, this paper proposes a practical method to obtain the undrained shear strength of clay and the friction angle of sand based on static cone pentration test (CPT) and standard penetration test (SPT) data.

  Method  Firstly, it introduced the method of rapid stratification based on the four basic data of CPT, aiming to divide the sand layer and clay laye. Then the method of calculating the empirical coefficient $N_{\mathrm{k}\mathrm{t}}$ of the undrained shear strength of clay based on the CPT parameters was introduced. Finally, a method of comprehensively considering CPT and standard penetration data and calculating the internal friction angle of sand based on empirical methods was introduced. Rseult According to the method of CPT parameter estimation, the obtained clay undrained shear strength is well compared with the laboratory test results which can obtain the clay undrained shear strength profile. The combined method of CPT and SPT can measure the friction angle of sand reliably, which fills the gaps of test data due to the difficulty in obtaining sand samples from offshore exploration.

  Conclusion  The method discussed in this paper can provide more reliable reference for determining th design values of soil strength considering the existing condition in which offshore survey methods are limited and the equipment resources are relatively scarce.