RAPID AND DYNAMIC LOAD TESTING OF INSTRUMENTED PZ27 STEEL SHEET PILES

1 online resource (284 pages) : PDF

2020

University of North Carolina at Charlotte

Pile foundations are typically used for structures underlain by weaker soils in order to increase the soil resistance and, subsequently, the axial capacity. In bridge abutments, sheet piles are typically used as facing elements for soil retention and scour control, however using these facing elements in the axial bearing foundation design is growing in interest. Currently, no guidance on the design of the sheet pile facing elements as axial load bearing members nor guidance on the use of rapid or dynamic testing of sheet piles for axial load capacity estimation is available. This dissertation produces full-scale rapid and dynamic load tests on instrumented steel sheet piles and performs in-depth analysis of the measurement data, in parallel with static load test measurements obtained from the same piles, to assess the application of a variety of different established methodologies for obtaining estimates of the axial load bearing capacity and load transfer mechanisms.Rapid load tests are classified to include loads with a duration greater than 5 but less than 5000 relative wavelengths, which produce significant dynamic soil resistance but are long enough in duration such that some complex dynamic phenomena, including stress wave propagation, are insignificant. This type of testing has been shown to predict the static axial bearing capacity more consistently than dynamic load testing, but requires larger equipment and setup than dynamic load testing. Several methodologies exist to analyze the results from rapid load tests, including the Unloading Point method, Modified Unloading Point method, Segmental Unloading Point method, and Embedded Data Collector method. In addition, there are also analysis methodologies that aid in estimating soil damping and rate effects that develop during a rapid load test. This dissertation presents a full-scale rapid load testing experimental program, in which four instrumented PZ27 sheet piles installed in a laboratory geotechnical pit are subjected to a large number of rapid loads varying in duration and amplitude. The Unloading Point method, Modified Unloading Point method, Segmental Unloading Point method, and Embedded Data Collector method are applied to the measurement data and the performance of each method in estimating the static soil resistance and load transfer are evaluated by comparison to direct measurements obtained from a static load test. Damping constants and rate effect parameters are also estimated using various methodologies described in the literature. The results are compared to empirical recommendations developed for bearing piles and the variation in these damping and rate effect parameters with load duration and amplitude is investigated.Dynamic load tests are classified to include loads with a duration less than 5 relative wavelengths, which is short enough in duration that complex dynamic phenomena, including stress wave propagation, are significant. This type of testing is particularly advantageous because it can be applied during driven pile installation and restrike testing, but it requires more complicated analysis methods to develop an estimate of the axial bearing capacity from the measurement data. The most common methods of analyzing the results of a dynamic load test are a relatively simple wave analysis approach called the Case method and a signal matching technique that involves inverse identification of parameters in nonlinear soil-structure interaction models within an analytical model of the pile. This dissertation presents a full-scale dynamic load testing experimental program, where a pair of instrumented PZ27 sheet piles and an instrumented H-pile are driven at a field site in Matthews, North Carolina. Dynamic testing of both piles is conducted during restrike testing performed one week after installation and subsequent static load testing is performed to obtain a direct measurement of the axial capacity and load transfer mechanisms. Total static axial bearing capacities are estimated from the pile driving measurements using the Case method and an automated signal matching program. The application of these methods to sheet piles is evaluated through comparison of the results to the static load test and to the results obtained for the reference H-pile. The variation of soil-structure interaction behavior with successive blows during driving, as estimated by the dynamic methods, is further investigated.

doctoral dissertations

Civil engineering

Ph.D.

Dynamic Load Test
Full Scale Load Testing
Rapid Load Test
Sheet Piles
Signal Matching
Unloading Point Method

Civil Engineering

Whelan, Matthew

Weggel, David
Pando, Miguel
Fang, Howie
Ogunro, Vincent
Cavalline, Tara

Thesis (Ph.D.)--University of North Carolina at Charlotte, 2020.

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Rice_uncc_0694D_12483

http://hdl.handle.net/20.500.13093/etd:2591