DISCUSSION ON A DIESEL HAMMER

THE SUBJECT PAPER PROVIDED ADDITIONAL DATA ON MEASUREMENTS OF FORCES AND DEFLECTIONS ACTING ON A PILE DURING IMPACT BY A DIESEL HAMMER. THE PRINCIPAL CONCERN OF THE DISCUSSOR IS THAT THE VALUES FOR ENERGY LEVELS TRANSMITTED TO THE PILE, AS FOUND IN THIS STUDY, MIGHT LEAD TO UNSAFE APPLICATION OF DYNAMIC DRIVING FORMULAS. THE CONDITIONS UNDER WHICH THE INVESTIGATION WAS CONDUCTED ARE NOT REPRESENTATIVE OF NORMAL PILE DRIVING OPERATIONS. RESULTS ARE COMPARED OF THE MICHIGAN STUDY WITH THE SUBJECT PAPER. IT IS THOUGHT THAT THE PRACTICAL SIGNIFICANCE OF THE PEAK FORCE RELATIONSHIP MAY BE OVEREMPHASIZED. THE SUBJECT REPORT DEVOTES CONSIDERABLE ATTENTION TO DETERMINING THE TOTAL POTENTIAL ENERGY OF A DIESEL HAMMER. IT IS CONCLUDED THAT THE ENERGY AVAILABLE FOR TRANSMISSION TO THE PILE IS, AT PRESENT, BEST DETERMINED BY ANALYSIS INVOLVING THE ONE DIMENSIONAL WAVE EQUATION. IT IS AGREED THAT THE WAVE EQUATION, AS APPLIED TO THE DATA, APPEARS MOST PROMISING. THE RESEARCH WAS EXTREMELY LIMITED AND REPRESENTS ONLY REFUSAL CONDITIONS FOR LONG CONCRETE PILES. THE MEASUREMENTS OF FORCE AND DEFLECTION, AND THE TECHNIQUES USED TO COMPUTE THE TRANSMITTED ENERGY, ARE SIMILAR TO THOSE USED PREVIOUSLY IN THE MICHIGAN PILE STUDY. THE AUTHOR'S REPLY TO THE COMMENTS MADE. THEY DO NOT SHARE CONCERN OVER THE USE OF DYNAMIC FORMULAE INVOLVING ENERGY LEVELS AS MEASURED HEREIN. THE DISCUSSOR EMPHASIZES THAT THE TEST CONDITIONS REPRESENT PRACTICAL REFUSAL ON A LONG PILE. THE WRITERS DISAGREE WITH THE STATEMENT THAT THE TEST PROCEDURES ARE SIMILAR TO THOSE USED IN THE MICHIGAN STUDY WITH RESPECT TO FORCE AND DEFLECTION MEASUREMENT. THE WRITERS' TECHNIQUES ALLOW A DETERMINATION OF ENERGY TRANSMITTED TO THE PILE, WHEREAS THE MICHIGAN STUDY FAILED ITS INTENDED PURPOSE DUE TO INTRODUCTION OF A LOAD CELL INTO THE HAMMER SYSTEM. THE DISCUSSOR STATES THAT ENERGY DELIVERED TO A PILE WILL VARY FROM ONE SET OF CONDITIONS TO ANOTHER. THE MICHIGAN STUDIES PROVIDE USEFUL INFORMATION ON THIS SUBJECT AFTER THEY HAVE BEEN ANALYZED USING THE WAVE EQUATION. THE WRITERS BELIEVE THAT THE LAWS OF MECHANICS CLEARLY INDICATE THAT ENERGY TRANSMITTED IS RELATED TO PEAK FORCE. THE WRITERS DISAGREE WITH THE STATEMENT THAT PROOF OF THE EFFECTIVENESS OF COMBUSTION PRESSURES HAS NOT BEEN OFFERED. THE EMPIRICAL FACT OF A LINEAR RELATIONSHIP BETWEEN PEAK FORCE AND TRANSMITTED ENERGY MAKES IT OBVIOUS THAT THE COMBUSTION CHAMBER PRESSURE IS EFFECTIVE, WHATEVER THE VALUE OF THE PRESSURE. THE DISCUSSOR HAS STATED THAT HAMMERS ARE RATED ACCORDING TO MAXIMUM KINETIC ENERGY PRIOR TO IMPACT. KINETIC ENERGY OF THE RAM AT IMPACT IS ALWAYS LESS THAN MANUFACTURER'S RATING DUE TO FRICTION, ETC. THE WRITERS AGREE WITH THE DISCUSSOR THAT A KNOWLEDGE OF THE FORCE- DEFLECTION-TIME RELATIONSHIPS AT THE PILE HEAD IS USEFUL FOR FUTURE RESEARCH. REFERENCES: ENERGY MEASUREMENTS FOR A DIESEL HAMMER, M.T. DAVISSON AND F.J. MCDONALD, ASTM STP 444, AMERICAN SOC FOR TESTING AND MATERIALS, PP. 295-313, 1969.

  • Supplemental Notes:
    • Stp 444, pp 314-337, 16 FIG, 6 TAB
  • Corporate Authors:

    American Society for Testing and Materials

    100 Barr Harbor Drive, P.O. Box C700
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  • Authors:
    • Ritchie, J M
  • Publication Date: 0

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  • Accession Number: 00232699
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Aug 15 2004 2:31AM