Location

Arlington, Virginia

Session Start Date

8-11-2008

Session End Date

8-16-2008

Abstract

Automatic SPT hammers typically provide more transferred energy to drill rods than traditional safety hammers. This results in lower measured blow-counts from automatic hammers when compared to safety hammers. To eliminate such deviations in blow-counts, quality assurance for licensing new generation nuclear power plants requires that SPT energy measurements be made for each hammer used so that blow-counts can be corrected and be appropriately used in foundation design. A series of SPT hammer energy measurements was conducted on automatic hammers using a pile driving analyzer and employing the force velocity method to measure the actual energy transferred into the system. This paper reports the results of measurements for several such subsurface investigations. Altogether, over 220 energy measurements were made on 32 different automatic hammers. The soils ranged from soft clays to partially weathered rock, and the sampling depths ranged from a few feet to over 400 feet. The results obtained are compared to the results from the studies of Florida DOT and Utah DOT. Analysis of the 220 ETR measurements gives an overall average energy correction factor of 1.36, with high and low values of 1.46 and 1.25, respectively, obtained by applying the standard deviation.

Department(s)

Civil, Architectural and Environmental Engineering

Appears In

International Conference on Case Histories in Geotechnical Engineering

Meeting Name

Sixth Conference

Publisher

Missouri University of Science and Technology

Publication Date

8-11-2008

Document Version

Final Version

Rights

© 2008 Missouri University of Science and Technology, All rights reserved.

Document Type

Article - Conference proceedings

File Type

text

Language

English

Share

 
COinS
 
Aug 11th, 12:00 AM Aug 16th, 12:00 AM

SPT Automatic Hammer Efficiency Revisited

Arlington, Virginia

Automatic SPT hammers typically provide more transferred energy to drill rods than traditional safety hammers. This results in lower measured blow-counts from automatic hammers when compared to safety hammers. To eliminate such deviations in blow-counts, quality assurance for licensing new generation nuclear power plants requires that SPT energy measurements be made for each hammer used so that blow-counts can be corrected and be appropriately used in foundation design. A series of SPT hammer energy measurements was conducted on automatic hammers using a pile driving analyzer and employing the force velocity method to measure the actual energy transferred into the system. This paper reports the results of measurements for several such subsurface investigations. Altogether, over 220 energy measurements were made on 32 different automatic hammers. The soils ranged from soft clays to partially weathered rock, and the sampling depths ranged from a few feet to over 400 feet. The results obtained are compared to the results from the studies of Florida DOT and Utah DOT. Analysis of the 220 ETR measurements gives an overall average energy correction factor of 1.36, with high and low values of 1.46 and 1.25, respectively, obtained by applying the standard deviation.