CPT, CPTu and DCPT Methods for Predicting the Ultimate Bearing Capacity of Cast In Situ Displacement Piles in Silty Soils

Determining the load-bearing capacity of piles using the results of in situ tests is one of the most widely used methods. The objective of this study is to examine suitable cone penetration test (CPT)-based methods for predicting the load-bearing capacity of piles in silty soils. In addition, it is analysed whether standard penetration test (SPT)-based methods can be used with dynamic probing super heavy (DPSH-A) test data to evaluate pile capacity. Five CPTs and one piezocone penetration test (CPTu) based on direct methods were applied to determine the load-bearing capacity of piles. In addition, six SPT direct methods were used based on DPSH-A test data to estimate the load-bearing capacity of the investigated piles. The capacity of the pile obtained by various direct methods was compared with the outcome of the pile load test. Of the direct CPT methods, the LCPC (also known as French method) method and the German method demonstrated decent results when CPT probing reached deeper than the pile. The use of SPT-based direct methods with DPSH-A test data for displacement piles in silty soils seems to be promising. Specifically, the Briaud and Tuckers` method provided excellent results for most of the piles studied.