The reference book "CPT in Geotechnical Practice" by T. Lunne, PK Robertson and JJM Powell references a work by Landva in which "Landva concludes that due to the fibrous nature of peat, and the frequent presence of obstructions like stumps and roots, small-scale in situ tests like...
Another good source of information is the Drilled Shaft Inspector's Manual written by Clyde Baker and published by "the international Association of Drilled Shaft Contractors" (ADSC).
