A Comparison between the Measured Load through a Load Cell and a Manometer on the Static Load Test in Piles

The static load test (SLT) in piles may provide the axial force applied at the top of the pile and its corresponding displacement. According to the ABNT NBR 12131, the measured load may be done through a calibrated manometer or a load cell installed in series with the hydraulic jack. However, according to the ASTM D1143, if the maximum test load will exceed 900 kN, place a properly constructed load cell or equivalent device in series with each hydraulic jack. The same load test can be represented by three different load vs. displacement curves (Load cell, manometer, theoretical SLT). The analysis of the results will be different depending on the corresponding curve that is used on the analysis, for example, the use of extrapolation methods to predict the ultimate load. The results revealed that static load tests performed in different project sites might present different over predicted manometer error rates when the hydraulic jack is loading and different under predicted manometer error rates when the hydraulic jack is unloading. The manometer error depends on numerous factors: eccentric and inclined load, the inclination of the reaction beams and the pile cap, manometer accuracy, possible influence of the residual force at the pile toe.