Benefits of Direct Push Sampling with a Geoprobe
Direct push sampling is a popular method for collecting soil and groundwater samples in the contaminated land site investigation industry. This direct push drilling method allows for rapid collection of high-quality undisturbed samples, which are then used for environmental testing and analysis. One of the most popular drilling rigs used for direct push sampling is the Geoprobe. In this blog post, we will explore the benefits and limitations of direct push sampling with a Geoprobe and other direct push tools.
What is a Geoprobe?
Geoprobe is a manufacturer of direct push sampling machines purpose built to collect soil samples without the use of drilling fluids or water. The Geoprobe DP rig consists of a hydraulic-powered top drive hammer that drives hollow steel rods into the ground. As the rods are pushed down, soil and groundwater samples are collected inside casing via a liner tube located in the lead rod. This sample line can be extracted whilst the casing remains in place minimising the possibility of cross contamination.
Benefits of Direct Push Sampling with a Geoprobe
1. High-Quality Samples
One of the key benefits of direct push sampling with a Geoprobe is the high-quality samples that it produces. Since the sampling tube is located directly at the end of the rods, there is no opportunity for cross-contamination of samples. Additionally, the samples are collected under in-situ conditions, which means that they are not affected by changes in temperature, pressure, or other environmental factors.
2. Rapid Sampling
Direct push sampling with a Geoprobe is a very rapid process. The hydraulic-powered rig can quickly drive the steel rods into the ground, and the samples can be collected with minimal impact to site operations. This means that the sampling process can be completed quickly, which can save time and money for site investigation projects.
3. Cost-Effective
Direct push sampling with a Geoprobe is a cost-effective method for collecting soil and groundwater samples. Since the process is rapid and does not require heavy equipment, it can be completed with fewer personnel and equipment than other sampling methods. This can result in significant cost savings for environmental investigations.
4. Versatile
Geoprobes are versatile crawler mounted, remote control drilling rigs that will go anywhere. They can be used to collect soil and groundwater samples, as well as to install monitoring wells and collect soil gas samples. This versatility makes them an ideal choice for many different types of environmental testing projects.
5. The ideal direct sensing platform
The combination of 15-20 ton hydraulic drive cylinder and top drive hammer makes the Geoprobe the perfect machines for completing High Resolution delineation of contaminated sites with the Membrane Interface Probe (MIP), Hydraulic Profiling Tool (HPT), Ultra Violet Optical Screening Tool (UVOST) and Cone Penetrometer Tests (CPT). Combine the latest technology vertical profiling with the ability to take physical samples and install groundwater and geotechnical instruments in a single mobilisation.
6. Minimise potentail for sample contamination
The dual tube Direct Push (DP) systems ensure the best possible integrity of the sample. Auger drilling and mud rotary methods provide very little certainty as to where in the bore the contamination is located. Most environmental consultants would never allow soil samples to be taken with auger methods in soils that could would be conducive to direct push drilling methods. It is important to carefully follow sampling protocols and to use proper decontamination techniques between sample locations.
Limitations of Direct Push Sampling with a Geoprobe
1. Limited Depth
One of the limitations of direct push sampling with a Geoprobe is that it is limited in depth. Depending on the soil conditions, a Geoprobe may only be able to collect samples to a depth of 20m or less. This can be a limitation for some environmental testing projects that require deeper sampling. For deeper sampling applications you would look at a Sonic drilling rig that can collect undisturbed samples to depths of up to 100m.
2. Limited Sample Volume
Another limitation of direct push sampling with a Geoprobe is that it produces a limited sample volume. The sampling tube at the end of the steel rods is typically only 40mm in diameter, which means that the samples collected are relatively small. This can be a limitation for some environmental testing projects that require larger sample volumes for analysis.
3. Possible shallow refusal
Direct push sampling with a Geoprobe is best suited for alluvial soils and clays. It is most effective in sandy or silty soils, where the steel rods can be easily pushed down. In dry, stiff or expansive clay soils, the rods may encounter signficant resistance, which can make the sampling process more difficult and less effective. Fine sands, saturated sands and cemented sands can also prove problematic sand is pushed inside the rod string during sample retrieval or fine sand can jam the liners or sample sheath in the casing.
Thanks for reading this article about direct push drilling methods and the best direct push tools. Our experienced staff at Legion Drilling Australia would be happy to talk through options for your next contained land investigation. With access to Direct Push, Sonic, auger, Diamond coring, MiHPT, UVOST, and CPT options we will get you the data you need to make a sound assessment of your next site.