3175 Turner Street
Abbotsford, BC V2S 7T9
2261 Cinnabar Loop
Anchorage, AK 99507, USA
The Becker Hammer drilling method consists of driving a string of double wall casing into the ground using a compact double-acting diesel pile driving hammer. Two sizes of Becker drill casing are commonly in use: (1) 5.5 inch OD x 3.25 inch ID and (2) 6.6 inch OD x 4.25 inch ID with two types of Becker drills, the AP-1000 and the HAV-180.
Both drill types utilize the same International Construction Equipment (ICE) Model 180 diesel pile driving hammer. Since its development in the late 1950s, the Becker drill has been widely used to obtain disturbed soil samples and, when driven with a closed bit, to provide penetration resistance profiles in the granular soils. This technique, the Becker Penetration Test (BPT), is much like a small pile driving test, and is especially useful to identify the density of granular soil sites where conventional drive-tube sampling techniques and Standard Penetration Test (SPT) cannot be efficiently utilized. The BPT penetration resistance, defined as hammer blows per foot, is often used in correlation to estimate SPT penetration resistance (N-values) in granular soils and other parameters to determine pile penetration and end bearing refusal elevations.
FBPT Mud Injection
The Foundex Becker Penetration Test (FBPT) consists of attaching an oversized closed bit to the Becker casing and a mud injection system to “lubricate” the casing. This lubrication permits driving the closed bit to deeper depths due to the decrease in rod friction. A new BPT-SPT correlation is recommended for the FBPT tests to correlate to the equivalent SPT-N value.60. The present correlation does not have a friction component. The test requires an independent site correlation of the SPT blow counts with the corresponding FBPT blow counts.
Ultimately the client can achieve deeper testing with this system.