What is Direct Push Technology (DPT):
A direct push machine “pushes” tools and sensors into the ground without the use of drilling to remove soil to make a path for the tool. Direct push machines rely on a relatively small amount of static weight combined with percussion as the energy for advancing a tool. Direct push tools do not remove cuttings from the probe hole but depend on compression of soil or rearrangement of soil particles to permit advancement for the tool string. Direct push tools are advanced as far as possible using only the static weight of the carrier vehicle. Percussion is applied as required when probing through sands, gravels, hard pans, high friction clays, tills and fill materials.
For many years, geotechnical and environmental investigations have employed conventional drilling using a hollow stem or solid stem auger to collect a sample. The technology has wide spread acceptance, but has several shortcomings that may now be overcome using direct push technologies.
Direct Push drilling technology (DPT) can be a cost effective, time saving, technically accurate means of drilling and sample collecting. This drilling method has been used for over 16 years.
Initially, direct push was primarily practical and effective in shallow (less than 20’ below ground surface (BGS), sandy or soft clay soils, but recent technological developments have expanded the range of soil types to include silt and gravel as well as increasing the depth range to more than 100’ or 30m. Such developments also have provided investigators with a variety of soil investigation options to choose from, as direct push systems work in conjunction with a number of sampling tools, and chemical and lithological indicator instruments. they also have become the primary method of installation of pre-packed monitoring wells.
The versatility of direct push does not end with the range of tooling, as some units are mounted on trucks, tracks and portable platforms. This variety of platforms offers the investigator the ability to sample areas previously considered inaccessible, including the inside of buildings. The portable platform is even small enough to fit through standard door ways. Although the truck mounted and portable geoprobe units may have a limited capacity possibly 20’-40’ (with 1″ well installs) our track mount rig have the ability to perform well in (unconsolidated soils) to much greater depths (up to 100’) with installation of 2″ monitoring wells. The Geoprobe unit has long been considered the “Cadillac” of DPT systems. They are also equipped with auger capabilities to give another option when required.
Conventional drilling can often create an expensive disposal problem. Waste cuttings often have to be placed into drums or bags and sampled for analysis prior to disposal. Costs associated with handling and disposing of drill cuttings can consume large amounts of the soil investigators budget. Direct Push generates little if any extra cuttings. In fact, an EPA study in 1998 found a cost savings of 25-50% may be achieved with many direct push sampling methods. Unlike methods that use rotary auguring to advance tools or install wells, thus generating a large volume of potentially contaminated drill cuttings, direct push methods use a hydraulically powered percussion hammer and the static weight of the vehicle on which the system is mounted. Tools are pushed or punched into the ground by displacing soil to make a path for the tool, thereby eliminating the generation of excessive drill cuttings. Decontamination time may be cut by up to 75%, as the casing is so small that it can be decontaminated in 5 gallon buckets.
Below are some of the popular techniques, conducted with a variety of methods, for varying lithologies.
Soil Sampling
Direct push core samples are representative of the true soil statigraphy and at the same time limits the amount of cuttings to be disposed of. Below the core sample taken is in gravels, proving the ability of Geo Probe Direct Push to get a representative sample in different soil conditions.
- Dual tube (DT325 – 3 1/4 inch ID Casing) discrete/ interval specific/continuous sampling 47mm core (1.85in)
Click here for more detailed information - Dual tube (DT45 – 4 1/2-inch ID Casing) continuous sampling with 75mm core (3in)
Click here for more detailed information - Macrocore / discrete sampling / interval specific / continuous 38mm (1.5in)
Click here for more detailed information
The above sampling methods may be used individually or telescopically to gain greater depth sampling.
Groundwater Sampling
- SP16 real time ground water sampler – This system provides a means of determining such chemical parameters as conductivity, ph, temperature and salinity. Click here for more detailed information
- Standard PVC wells – sizes from 19mm (1/2in) to 100mm (4in)
Standard 2 inch PVC monitoring wells or pre-packed monitoring wells from 3/4″ to 2.5″ OD can be installed using 3 1/4″ hollow push rods with an expendable tip. Using the 3 1/4″ rods are similar to well installation using hollow stem augers, without the excess cutting and time involved with auger use. This makes well installation in loose soils such as sand and gravel quick and easy. In the rare occasion augers are needed our rigs come equipped with 4 1/4″ augers for sampling or well installation.
- Prepack monitoring wells – sizes from 19mm (1/2in) to 50mm (2in)
Click here for more general information about Prepacked Screen Monitoring Wells
Click here for information on Prepack versus Standard PVC wells
Click here for Prepack Standard Operating Procedures
What is a pre pack screen? – Pre pack screens consist of a standard slotted, PVC screen pipe surrounded by a stainless steel mesh. Sand is packed between the slotted PVC and the stainless steel mesh. Since the sand is packed around the slotted PVC before the well screen is installed, using prepacks guarantees that sand will be located directly around the well screen. This makes well installation quicker and more efficient than conventional methods.
Soil Gas Sampling
- Real Time Soil Gas Sampling – Post Run Tubing (PRT)
Click here for more detailed information - Direct Push Soil Gas Implants (Wells)
Click here for more detailed information
Concrete Coring & Breaking
- Concrete Coring with Geo-Probe Rig – 250mm (10in) Core
Click here for more detailed information - Concrete Breaker Drill – Able to drill a 100mm (4in) hole in concrete (similar to a hammer drill)
Auger Drilling
- If soil conditions prohibit Direct Push Drilling our Geo-Probe unit has the capability to use solid and hollow stem augers.
Direct Push benefits
- Variety of technically accurate tooling capabilities for soil, soil gas, and groundwater sampling.
- Less labor intensive
- Minimum generation of drill cutting during the sampling process for disposal
- Generally quicker and more mobile, allowing easier access to low clearance, limited access and off road areas.
- Quicker probing capabilities, with typical penetration rates from 2-6m/min. (continuous push)
- Quick collection of conformation borings for site closure
- Flexible enough to add auger capabilities to the direct push options
- Creation of small diameter holes, minimizing surface and subsurface disturbance
- Capable of angle probing
- Accurate geotechnical testing for remedial investigations and injection activities
- Drills easily through surface pavement up to .31m (concrete coring)
