Steel driven piles have been around since the early 1900s and continue to be used effectively. With steel piling, one uses HP steel shapes. HP is so named because, looking at the end of the steel shape, it is in the form of the letter H. P stands for pilings, hence the HP. These sections can be both the bearing type as well as friction.
While steel piling continues to be a viable option, there are a couple of new systems we have been using: Spiralweld pipe and the DTH method of hammer and casing advancement.
In the past, API 9 pipe (steel casing pipe) was used extensively, but new trends are to use spiralweld pipe. While this type of pipe has been around for decades, we are seeing more of it used now with deep foundations because of manufacturing and technological advances.
Spiralweld is made from large coils of steel which are welded internally and externally in a spiral as the coil is unrolled. This forms the desired pipe size. Spiralweld pipe can be made in many custom sizes to exactly fit the needs of the job, thus saving cost. It can get to the market/job site in less time. It’s not uncommon now for typical sizes to range from about 3/16” to 1” thick with diameters from 10” to 120”.
Down the Hole (DTH) hammer and casing advancement systems.
In this system, the DTH hammer and casing advancement system have been combined to offer a cost effective solution in sensitive ground. The DTH hammers have been around for quite some time, but combining this technology with a casing advancement system allows for the casing to be installed as the hole is being drilled in any ground condition. This method is particularly superior when boulders are present or the bedrock is inclined.
Installing the casing in this manner allows for greater control and accuracy of the casing placement. This method permits installation of casings on a batter as well. Typical diameters are currently available up to 42”.
Have you used DTH hammer and casing or spiralweld pipe? Can you share any advantages?