Formulation and Assessment of SPT Hammer Energy Transfer based on Energy and Momentum Conservation

Samuel J. Rahon

Thesis (MS Civil Engineering) - University of the Philippines Diliman -2007


The study focused on the formulation and assessment of new equation for hammer energy transfer to a Standard Penetration Test (SPT) drill rod based on energy and momentum conservation. Standard Penetration Test hammer energy transfer dealing with loss of energy on long penetration was analyzed theoretically. Theoretical energy computed using the new equation and existing equations and/or models was compared with the results of field testing to assess the performance of each formula and/or models. Assessment of existing equations and/pr models was done by using SPT field energy measurement data of Geotechnics Philippines Incorporated. Standard Penetration Test was undertaken in accordance with the Standard Test Method for Penetration Test and Split-Barrel Sampling of Soils (ASTM D1586). Simultaneous with ASTM D1586, the SPT instrumented/calibrated rod was inserted to the drill rod connected to the Pile Dynamic Analyzer that displays force, velocity and energy transmitted to the drill string for each hammer blow. Auto-trip hammer was used to eliminate operator-related such as the hammer free and free fall height.

Results of comparison with existing equations and/or model show that all the equations agree well at rod length less than 10.5m however the new equation is deriviated with the existing equations beyond the said length. Existing equations has a constant energy transfer starting at length of 10.5m while the new equation decrease with increasing rod length. This trend is confirmed by the actual data from field energy measurements of eight rod lengths from five SPT hammers of Geotechnics Philippines Incorporated.

Subjet Index : Energy tranfer, Energy conservation, Momentum distributions