Pile Driving Refusal Assessment of Steel H-Piles in Schist Saprolite

A better understanding of pile driving resistances and anticipated refusal depth is important to manage installation risks and reduce potential cost. A study to evaluate the performance of steel H-piles driven into thick Wissahickon Schist saprolite layers was conducted for a bridge project in southeastern Pennsylvania. The pile driving resistance is further investigated through a bridge project for these intermediate geomaterials which are completely weathered but retain the fabric and structure of the parent bedrock. All piles in this study were driven to Pennsylvania Department of Transportation (PennDOT) Case 2 Absolute Refusal, defined as 20 blows per inch in soft or decomposed rock, or dense or hard soil strata. Geotechnical resistances from Case Pile Wave Analysis Program (CAPWAP) were compared to evaluate the pile driving refusal criteria. In addition, hammer transferred energy, maximum induced stress as well as pile embedment into saprolite are summarized. The paper presents the results of the pile driving refusal criteria assessment study and provides recommendations to guide both the pile length estimation and geotechnical resistance prediction during the design phase for future projects with similar challenges.