The interface friction b/w soil and pile could be evaluated by conducting direct shear test. The results obtained from the test can be used as input parameters in your model study. but interface friction parameters is given with respect to type of piles & soil in many of the standard text book.. you could refer the following text book..
Poulos & Davis .- Analysis and design of pile foundation..
Michael Tomlinson and John Woodward, Pile design and construction practice, Taylor & Francis Group, London & New York, 2008 ..ok all the best in your research work..