Abstract: To identify boundaries of homogeneous soil layers is critical to geotechnical design. The piezocone penetration test (CPTU) data are often used for soil classification, boundaries identification, property evaluation, etc. Statistical methods for soil boundary identification are developed to detect the boundaries of the homogeneous soil layers based on CPTU data. To generate intra-class correlation coefficient index, i.e. RI statistics and Bartlett statistics, it is necessary to perform statistical analysis on CPTU data with intra-class correlation method and modified Bartlett statistic test respectively. The boundaries of homogeneous soil are identified by mechanical layered method using critical RI statistic and critical modified Bartlett test statistic for homogeneity test of soil layers. The CPTU data in three construction sites are assessed to identify boundaries of homogeneous soil layers with the proposed methods. The results compared with the results of the soil classification layered method show that the mechanical layered method can discriminate all primary boundaries decided by the soil classification layered method, and reveal potential secondary soil boundaries.

Key words: piezocone penetration test, soil boundary identification, mechanical layered method, statistical analysis