Numerical Modeling as a Tool to Assess Empirical Methods for Interpreting O-cell Pile Load Test Results

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The bidirectional (O-cell) test is a relatively new method of pile testing that is used when the test loads are high. In contrast to the single load-settlement curve resulting from the conventional (top-load) test, the results of the O-cell test consist of three separate curves. Efforts were made over the years to find a way to interpret the results of the O-cell test by transforming them to what is known as the Equivalent Top Load (ETL) curve. Many methods were proposed by different researchers to construct ETL curves. With the help of numerical modeling, this paper assessed the available empirical methods. Finite Element (FE) models were developed to simulate O-cell tests. The models were calibrated based on the data of well-documented case studies of O-cell tests. Then, the calibrated models were used to simulate the equivalent conventional tests to find their corresponding load-settlement curves. A total of seven methods for constructing ETL curves were applied to the data of the case studies to be assessed. The seven different ETL curves found from each method were compared to the load-settlement curve produced from the simulated equivalent conventional test (reference curve). The comparison was mainly based on finding errors in the values of ultimate load-carrying capacity and settlements at expected working loads estimated from each ETL curve. The results of this paper showed that the errors produced by all the available methods are significantly high. Thus, it is important to develop a new method that minimizes errors.

4th Asia-Pacific Conference on Physical Modelling in Geotechnics (ACPMG2024)

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