April 8, 2019
To answer that question, it generally very much depends on the project requirements, site conditions, application or other factors. However, pipes do get filled with concrete because there is a need to increase the capacity of the pile or the combi-wall itself.
In a marine environment, you could fill pipes to limit corrosion inside of a steel pipe pile that is subject to tidal fluctuations. Other times, the pile is designed as a concrete pile with a left-in-place casing, where the casing is sacrificial and not considered in the design.
If the steel pipe alone is sufficient in the specification, it can be more economical to add thickness to account for corrosion rather than drilling out the pipe and filling with concrete.
Of course, again, with anything in the pile driving industry, the answer to that question can truly only be assessed on a case-by-case basis.