CPT & CPTu Application for Deep Foundations Geotechnical Design; Databased Approach
Abolfazi Eslami, AUT; Barmak Biron; and Masoud Nobahar, LSU-LTRC 

The Cone Penetration Test (CPT) and Piezocone (CPTu) play a crucial role in geotechnical pile design due to their simplicity, cost-effectiveness, and ability to provide continuous records with depth. The CPT data results are interpretable on both empirical and analytical bases, and they can incorporate various sensors to measure different soil parameters, leading to a large database of experience-based knowledge. The primary datasets provided by CPT and CPTu can be used based on tip resistance, sleeve friction, and pore pressure, which are highly applicable to geotechnical pile design. Its main advantages include rapid application, economical aspects, and reduction in operator influence, making it an increasingly preferred method over other available in situ tests. Several methods utilize CPT data for predicting geomaterial properties in foundation design, including empirical methods, simplified analytical methods, numerical analyses, and soft computing. Due to the similarities between the cone penetrometer and pile behavior, it can be used to determine pile capacity with necessary amendments and modifications regarding scale effect and installation. Accordingly, factors such as penetration rate, strain level, type of execution, data processing, influence zone, and ultimate load criteria should be considered.

In the design process of deep foundations, it is essential to integrate CPT data with geotechnical aspects such as bearing capacity, settlement, embedment location, and the possibility of surrounding soil instability. The continuous records from CPT soundings provide a detailed profile of soil behavior, tip resistance, and sleeve friction, which are critical for assessing soil strength and stiffness variations at different depths. Available pile design approaches are static analysis, dynamic approaches, load testing, empirical and in situ-based methods. Recent advancements in in situ testing have enhanced the reliability of CPT-based methods for pile design. Direct approaches estimate pile unit shaft and tip resistance directly from CPT records, while indirect approaches use CPT data to derive soil strength parameters for static analysis. In the past 60 years, after the 1960s, more than 30 CPT-based methods have been developed and employed by different entities worldwide. Despite the diversities between methods and geographic locations, most of the predicted pile capacity is in a reasonable and promising range compared to the measured one. The methods employed either locally or internationally have been developed essentially based on a comprehensive knowledge base database.

This course will provide an in-depth understanding of CPT and CPTu implementations and their role in pile geotechnical design, including installation, bearing capacity, settlement, and resistance distributions. Participants will gain insights into practical applications, methodologies for pile design discussed analytically, and case histories to understand the applicability of CPT in pile design. The program includes a review of selected well-known methods that discuss the database approaches in detail.  Overall, the program will also provide real-world examples of challenging conditions in pile design. A recap and Q&A sessions will allow participants to engage in discussions to solidify their professional implementation.

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