Abstract

Static load tests on foundation piles are generally carried out in order to determine load – displacement characteristic of the pile. For more detailed information, e.g. force distribution along the shaft, load transfer mechanism and characteristics of soil-structure interaction (unit resistance curves t-z, q-z) additional pile instrumentation is required. Most popular techniques focus on direct concrete strain measurements and their conversion into calculated loads. However, proper determination of that forces requires the exact value of pile material stiffness (EA). Due to difficulties in determination of that stiffness, additionally hampered by the practical lack of knowledge about the pile shafts real geometry, very often the interpretation results of instrumented load tests are inadequate and can be subjected to significant errors. This short paper presents general problems concerning the determination of reinforced concrete properties used to interpret the results of static load tests on instrumented piles. Characteristics of elastic modulus variability with strain and depth, shaft deformations and possible changes in cross section area are determined. Several case stories of instrumented pile load tests, geometry check, material laboratory testing are discussed in the paper and will be presented during the conference.

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