Geology plays a decisive role in the success of diamond drilling. It is a fundamental part of construction site evaluation. It helps reveal the conditions beneath the ground and gives engineers and architects insight into potential environmental hazards. Lack of geological information results in total failure of drilling operations.
Factors responsible for good core recovery can be classified into many segments. Among these, two main factors are – geological, and the other is geotechnical. Geology involves lithology, rock mechanics, stratigraphy, groundwater, structure, mineralogy, weathering and rock mass composition. In contrast, geotechnical consists of choosing a perfect rig, coring bits, core barrel, drilling fluid, weight on bit (WOB), revolutions per minute (RPM), and borehole cleaning drilling fluid pressure.
Diamond drilling Kent helps create geotechnical holes. It is also known as engineering holes. Some of the most common geotechnical drilling techniques include mud rotary drilling, hollow stem auger drilling, and solid stem auger drilling. Depending on your site conditions, you may need to use one or more techniques.
Please read on to learn more about geotechnical drilling techniques.
Table of Contents
Mud Rotary Drilling
It is a geotechnical drilling technique chosen for its speed and adaptability. This technique lubricates the drill bit with pumped drilling fluid; it is typically water combined with various other fluid enhancers, allowing the drill bit to stay calm. It pressurises the hole and keeps the walls of the bore in place by minimising caving.
Advantages of Mud Rotary Drilling
- Efficiency: Fat and drill up to several hundreds of feet of soil per day if needed.
- Flexibility: It can work in a vast array of soil conditions.
- Range of Soil Sample: Supports sediment as sampling as well as thin wall and split barrel sampling.
However, mud rotary drilling does have some disadvantages, especially regarding the necessary drilling fluid. When the liquid gets pumped, it can disturb the investigation area and compromise with sample findings. It is also not suitable where environmental wells are needed.
Hollow Stem Auger Drilling
It is sometimes used for soil sampling to set groundwater monitoring wells. It helps understand water conditions and patterns around the construction site; it is essential to know this as they will affect the overall scope for the planning of your foundations.
Advantages of Auger Drilling
- Facilitates water sampling.
- Helps install monitor wells.
- Fewer turnaround times.
- It can operate without drilling fluids.
- It can perform more external applications.
It is one of the most reliable and oldest forms of drilling. It is a small, manoeuvrable, lightweight rig that is used for setting groundwater monitoring wells and geotechnical applications.
Solid Stem Auger Drilling
This technique excavates and transports samples and cuttings to the surface for future study, using continuous drilling in a range of diameters. It produces reliable results with smaller rigs compared to other drilling techniques.
Advantages of Solid Stem Auger Drilling
- Produces a good amount of samples.
- It does not require drilling fluid.
- One can use it with smaller rigs which are economical and easier to manoeuvre.
It is a more labour-intensive geotechnical drilling technique as it demands removing an auger after drilling the hole. It would be beneficial if you use this technique with solid soils that are not at risk of collapsing during the drill’s removal.
Rotary Vibratory
This technique has become famous under solid environmental restraints. It is a dual-cased system which uses high-frequency mechanical vibrations to provide continuous core samples. The string vibrates at adjustable frequencies between 50 Hz and 150 Hz and is rotated slowly in more intricate formations to distribute energy and bit wear. It is adjusted to achieve maximum penetration rate by coinciding with the natural resonant frequency of the drill string, providing high energy to the bit. In soil, it also laterally displaces the particles by greatly facilitating penetration.
Advantages of Rotary Vibratory
- It can provide constant samples in soil.
- It can penetrate obstructions and any other variable condition.
- It drills up to 500 feet.
- It converts some rocks and does not require a flush.
Some geotechnical construction-related applications do not allow conventional flushed drilling systems. During such time, rotary vibratory demonstrates the exceptional potential for rock and soil drilling in some specific combinations of situations.
Rotary Percussive Drilling
Also known as down-the-hole hammers (DTH), rotary percussive drilling generally determines the penetration rate. The drill principle embodies the combination of percussion and rotation. The top hammer rotates the drill rods and is percussed by the drill head on the rig. With a direct circulation, DTH drill rods are only revolved by the drill head. Compressed air feeds down the rods and activates the percussive hammer mounted directly above the drill bit. There is a forced back out at the mouth of the borehole through the annular gap between the drill pipe and the borehole, along with the loosened drill cuttings. Although, special procedures can also involve flushing with water through the drill pipes, down the hole hammer and drill bit.
Advantages of Percussion Drilling Holes
- 5x or more and consistent penetration rates compared to rotary methods.
- This technique uses small, mobile, and lightweight drill rigs.
- Cost-effective.
- Provides potential for minimal hole deviation with production rates of 15 feet per hour to 500 feet per hour.
In this technique, the hammer, bit, compressed air or fluid arrangement allows much deeper percussion. However, DTH drills are more expensive compared to other kinds of drills.
The fundamental objective of core drilling in geotechnical work is to document, classify and analyse the rock mass conditions in terms of suitability for various geotechnical drilling techniques described above.
Conclusion
Our professionals provide excellent geotechnical drilling services. Their exceptional technical expertise and dedication will help you execute the operation in the most precise and safest manner based on geological information. They understand the site’s geology and all the drilling systems with integration, allowing them to plan an effective core drilling operation for your project. To get the complete geotechnical report, contact diamond drilling Kent.
