BEARING CAPACITY ASSESSMENT OF ROOT PILES INSTALLED IN SOIL–ROCK COMPOSITE STRATA

Abstract

The bearing capacity of piles is one of the most important estimations in geotechnical engineering. One of the most commonly adopted pile types in foundation design is the micropile, locally known as a "root pile", which is a type of injected pile installed under pressures of up to 500 kPa during shaft formation. The bearing capacity of root piles is typically determined based on static load tests performed after pile installation. Several theoretical, semi-empirical, and empirical methods exist for estimating the bearing capacity of root piles used in Brazil and worldwide; therefore, it becomes essential to verify the efficiency of commonly applied methods and their applicability during the design stage. The objective of this study is to evaluate semi-empirical methods commonly used in Brazilian foundation design practice for estimating the bearing capacity of root piles based on SPT and rotary drilling (coring) data, through comparison with static load test results. SPT and rotary drilling investigations were performed, along with the construction of two root piles with a diameter of 410 mm and a length of 7.7 m. Finally, static load tests were carried out for each pile. Based on this evaluation, the methods proposed by Aoki and Velloso (1975), Décourt and Quaresma (1978), and Williams and Pells (1981) showed the best performance in predicting the bearing capacity of root piles installed in soil–rock stratigraphic profiles in the municipality of Fortaleza, Brazil.