Senior Staff Engineer Terracon Los Angeles, California, United States
Purpose: Pile load testing programs provide site specific empirical data of both the drivability of the site and the behavior of piles subjected to series of applied loads. When performed as part of the planning and design stages of solar projects, the results can help contractors and owners develop efficient foundation designs and more accurate estimates of construction schedules.
Methods: Pile load testing is an important factor of design and construction quality control for solar power projects. When installing test piles, using similar pile driving equipment to what will be utilized during the project construction phase provides valuable information regarding the resistance, drivability and anticipated driving times of the proposed piles and they also provide more accurate information than the theoretical formulas based on the soil conditions. The test procedure involves applying an axial load to the top of the test pile with one or more hydraulic jacks. Various forms of instrumentations are installed onto the test to obtain an accurate measurement. Pile testing methods have evolved to provide more reliable results and improved safety during testing. The vertical and lateral capacities of the piles are a function of following engineering properties of the subsurface soils: â– soil type, â– density, â– cohesion, â– soil friction angle Pile load testing provides a way to model the subsurface site conditions, enabling the designer to assess multiple loading conditions and pile sizes. These resulting soil models can be utilized in: â– to better interpret the soil/structure interaction of the solar foundation â– to compute deflection, bending moment, and shear force over the length of the pile The soil parameters developed from the testing are often higher than generalized theoretical predictions of similar soil types. Pile load tests can be modified to develop engineering solutions for sites with subsurface issues such as shallow refusals, adfreeze depths, and expansive soils. Summary of
Results: In summary, utilizing innovative pile load testing methods not only can help with the validation of the theoretical assumptions, but also provides the owner, design engineer, and/or contractor with cost effective design parameters and site-specific information to support the project construction timeline.
