WorldWide Drilling Resource

National Drilling Association Tel: 877-632-4748 Fax: 216-803-9900 www.nda4u.com 11 WorldWide Drilling Resource ® MAY 2013 SPT Introduction by Scott Cosby The article this month will focus on another foundation test our crews reg- ularly employ in the field. The main pur- pose of the Standard Penetration Test (SPT) is to drive a split-barrel (or split- spoon) sampler to obtain a representa- tive soil sample for identification purposes, and measure the resistance of the soil to penetration of the sampler, often re- ferred to as “N” values. A further exam- ination of the SPT in terms of the tools and methods, as well as the importance of “N” values will give the reader a bet- ter understanding of this geotechnical test. Improvements in technology and methods concerning the SPT have been continuous up to present day since the test’s initial development in 1902 by Charles Gow, owner of Gow Construction Company in Boston. The SPT test re- quires four items to perform the test, which is similar to the TCP (Texas Cone Penetration) test as we discussed in the April 2010 WWDR article: o Hammer system (either automat- ic or cathead driven) weighing 170 pounds with a 24-inch drop. o Anvil with fitted threads to the drill stem used. o Drill stem in appropriate length to reach the test depth. o SPT or split-spoon with OD (out- side diameter) of 2.0 inches, ID (inside diameter) of 1.0 inch or 1.5 inches, and a tube length of 18.0 to 30.0 inches. The SPT or split-spoon is the cen- terpiece of this testing method, and is made of four parts: sampler head; split- barrel sampling tube; driving shoe; and metal or plastic basket (also called a catcher) to hold the sample within the driving shoe. At the target borehole depth and after excessive cuttings have been re- moved, the split-spoon sampler is at- tached to the drill stem and lowered into the borehole. The hammer is posi- tioned above, the anvil is attached to the top of the drill stem, and the ham- mer system is placed over the anvil. The split-spoon is driven 6 inches into the ground, then the number of blows need- ed for the tube to penetrate each 6 inches, up to a depth of 18 inches, is recorded. The total sum of the number of blows required for the 2nd and 3rd 6 inches of penetration is termed the "N-value". These N-values provide an indication of the material’s characteris- tics, and can be used in many geotech- nical engineering formulas. Consult online search engines for manufacturers and more information on this topic. ASTM D1586 - 11, Standard Test Method for Standard Penetration Test (SPT) and Split-Barrel Sampling of Soils is a useful reference for the stan- dard penetration test. Scott Scott Cosby may be contacted via e-mail at admin@ worldwidedrillingresource.com Driving Shoe Sampler Head Basket Split-Barrel Sampling Tube(s) DFI Hosts SuperPile This Month Adapted from a Press Release by Deep Foundations Institute The DFI (Deep Foundations Institute) will host its annual SuperPile conference this month in Minneapolis, Minnesota. The conference will take place at the Hilton Minneapolis, May 15-16. SuperPile 2013 will include 40 ex- hibitors, and more than 20 technical pre- sentations on subjects including: C Driven piles C Micropiles C Marine foundations C Drilled shafts The effects, changes, and response of Hurricane Sandy will also be evaluat- ed at the conference with guest speakers discussing the natu- ral disaster. Gregg Piazza of Mueser Rutledge Consulting Engineers wi l l ad- dress “Hurr icane Sandy, Rapid Response Inspection, and Coastal Flood Protection”, and Dr. Thomas Herrington will speak about the Center for Maritime Systems, as well as possible changes to federal flood maps since the storm. Additional information on SuperPile 2013 is available at www.dfi.org Gregg Piazza