Analysis of Bored Piles' Field Test Results

Abstract

The purpose of the study is to establish accuracy of determining the load-bearing capacity of bored piles according to the method specified in Regulations 24.13330.2011 "Pile foundations". Relevance of the topic is determined by the following: the load-bearing capacity of a pile is a fundamental indicator affecting all subsequent activities related to foundation design, and accuracy of analytical solutions for complex engineering and geological conditions is highly questionable. Field tests of bored piles were carried out in engineering and geological conditions of Saint Petersburg with deformation modulus from 10 to 40 MPa at a load in the range from 1,000 to 6,300 kN, at achievement of absolute settlement of 40 mm. Piles with a diameter from 0.15 to 0.88 m and a length from 10 to 47 m were made using various technologies: using casing, using slurry, using a flight auger. Following the results of field tests, diagrams of load-bearing capacity of piles according to the material, depending on geometrical parameters and manufacturing techniques, diagrams of actual and designed load-bearing capacity of piles were plotted. Approximating functions to describe the dependences were obtained. According to the analysis of the results, it is possible to conclude that the load-bearing capacity of the bored pile during field tests is 1.4–1.7 times higher than the load-bearing capacity of the pile designed according to Regulations 24.13330.2011; the average share of the load-bearing capacity along the side surface of the pile was 65% and under the pile toe — 35%.