BEP Shaft Rescue Robot (2022/2023, Q3)

Borehole/Well Analysis (source: https://wikiwater.fr/E28-Various-types-of-wells-and-boreholes-General-points)

During the analysis of the different incidents, it was found that most of the cases involved either wells or boreholes. Thus further research into the specifications of these holes should be done.

Wells can be classified into three types :

• hand-dug wells
• driven wells
• drilled wells or boreholes

In this section the different types of wells will be explained and there will be a analysis on the dept, diameter and the change of collapse.

Hand-dug Wells

With the exception of modern wells, these wells are manually dug holes in the ground using shovels, picks, and similar tools. Typically, they are not very deep and range from 8 to 20 meters. There are two main catogrories of Hand dug wells these are traditional wells and modern wells.

Traditinal wells

Traditional wells are constructed using local resources and traditional methods, often with the assistance of professional well-diggers. These wells are dug by hand without concrete spouts, and the walls are supported only by wood or branches. The diameter of these wells varies, but they tend to be smaller than modern wells. Traditional wells can be split up into two subsections, temporary wells and permantent wells.

Temporary wells

Temporary wells are quickly constructed with simple linings of branches or straw and are typically less than 10 meters deep. However, they require regular reinforcement to prevent collapse, and the amount of water they can supply is limited.

Permanent wells

Permanent wells are dug deeper, often reaching depths of 10-20 meters or more. Experienced well-diggers construct these wells, and the diameter typically ranges from 0.8 to 1 meter. Although they have a longer lifespan than temporary wells, the walls of permanent wells may deteriorate over time if not supported adequately.

Modern wells

Modern wells are often constructed with mechanical digging equipment, although hand digging may also be used. The diameter of these wells varies from 1 to 1.8 meters, and the walls are firmly supported by a metal or concrete casing. The wells are topped with a margelle (coping) and protected from animals.

Change of Collapsing

Temporary digging wells are typically shallow and used for short periods. These wells have a higher chance of collapsing due to their lack of structural stability, which can result in injuries and fatalities. The walls of these wells are not lined with any materials, which increases the risk of collapse. Additionally, temporary wells may be dug in areas with soft soils, which can quickly erode, further increasing the risk of collapse.

Permanent wells are designed for long-term use and are more structurally stable than temporary digging wells. These wells are typically lined with concrete, stone, or brick to prevent collapse, and often have a mechanical pumping system in place to draw water. Although permanent wells are less likely to collapse than temporary wells, they still require regular maintenance to ensure their structural integrity.

Modern hand-dug wells are a more recent development and use modern materials and techniques. These wells are typically lined with precast concrete rings or PVC casing, which makes them more structurally sound and less likely to collapse. Modern hand-dug wells are also designed to allow for easy installation of pumps and other accessories, making them more convenient to use and maintain.

Driven Wells

A driven well, also known as an instantaneous well or sand-point well, is a capture-engineered structure that is dug vertically by driving a perforated pipe with a pointed end directly into the ground using a variety of techniques until it reaches the water table. This technique is suitable for soft or medium-hard ground.

Driving Techniques

There are different driving techniques for driven wells:

• Percussion driving
• Water injection driving
• Undercutting driving

Depending on the driving technique used, driven wells can have varying diameters and depths, with the desired flow rate also playing a role.

Small-diameter wells with depths of less than 15-20 meters can be dug using percussion driving. Water injection driving can dig wells up to around 30-40 meters deep, while large-diameter wells with depths of 15-20 meters can be dug using undercutting driving. However, driven wells are generally limited to shallow or average depths of less than 40-45 meters and are more exposed to contamination and drying out during periods of drought.

Change of collapsing

The manufacturing method of a driven well can have different effects on the surrounding ground, depending on the driving technique used.

Percussion driving involves driving a pipe into the ground using a heavy tool and has the potential to cause the ground to collapse. This technique is not suitable for hard ground and requires the ground to be free of stones or rocks. If the ground is at risk of collapsing, a preliminary well casing must be inserted and removed when the final pipe is installed.

Water injection driving involves injecting water under pressure to create a hole in the ground. The water wells up at the bottom of the hole outside the pipe walls and rises to the surface of the ground as mud containing the ground cuttings. This mud can stabilize the walls of the well, reducing the risk of collapse.

Undercutting driving involves constructing a large-diameter pipe and digging inside it to lower it gradually. The weight of the pipe pushes it downwards as the digging progresses, and the earth is dug out from inside either manually or with a mechanized bucket that empties the inside of the pipe. Due to the large diameter of the pipe, this method has a lower risk of collapse than percussion driving. However, it may not be suitable for hard ground or areas with rocks or large stones.

Drilled wells or boreholes

Bored wells are an effective method of sinking wells, allowing for quicker and deeper digging than traditional hand-dug or driven wells. This method involves drilling a cylindrical hole vertically into the ground using a cutting tool such as an auger or drill bit, with the diameter of the well ranging from 5 cm to 1.5 m. Most bored wells are equipped with a water pump, which can be manual, motor-driven or submersible, chosen based on factors such as the well's depth, the desired flow rate, and available resources, both technical and financial.

Borehole drilling methods vary based on geological characteristics, depth, flow rate, and borehole diameter. Manual drilling is cost-effective, suitable for shallow depths and soft ground, and uses cheap manual tools such as augurs. Boreholes with diameters between 50-140mm are drilled manually, while mechanized drilling is used for diameters ranging from 100-160mm for light equipment and up to 1500mm for heavy machinery.

Manual drilling techniques include hand-auger drilling, percussion drilling, jetting or washbore drilling, and rotary manual or rota sludge drilling. Hand-auger drilling is used for depths up to 15-25 meters and soft ground. Percussion drilling can be used for depths up to 25 meters and is commonly used for drinking water. Jetting techniques, including rapid pressurized jetting and rotary manual or rota sludge drilling, can be used for depths up to 35 meters and 40 meters, respectively.

Mechanized drilling methods such as compressed air percussion drilling use compressed air to drive a drill bit into the ground. This technique is commonly used for deeper boreholes, up to hundreds of meters deep, and in hard ground. The diameter of these boreholes can range from 76-203 mm, depending on the specific needs of the project.

Change of collapsing

The likelihood of borehole collapse can vary depending on the drilling method used. Generally, manual drilling methods have a higher risk of borehole collapse than mechanized drilling methods. This is because manual drilling often relies on human power and does not provide as much control over the drilling process, which can result in irregular borehole shapes that are more prone to collapse.

Hand-auger drilling, for example, typically results in a borehole that is relatively narrow and straight, which may be more prone to collapse than other methods. Percussion drilling and jetting methods, on the other hand, tend to create a more irregularly shaped borehole that can be more resistant to collapse. Additionally, these methods often involve the use of drilling fluids, which can help to stabilize the borehole and prevent collapse.

Mechanized drilling methods, such as compressed air percussion drilling, typically have the lowest risk of borehole collapse. This is because these methods involve precise control over the drilling process, allowing for the creation of a smooth and consistent borehole shape that is less prone to collapse. The use of drilling fluids in mechanized drilling methods can also help to stabilize the borehole and prevent collapse.

TEAM:

• Luke Alkemade (l.n.alkemade@student.tue.nl)
• Arif Ashworth (a.j.ashworth@student.tue.nl)
• Guillem Ribes Espurz (g.ribes.espurz@student.tue.nl)
• Stijn Michiels (s.f.h.michiels@student.tue.nl / +31 6 12871230)
• Vadims Kisels (v.kisels@student.tue.nl)
• Thomas Leniere (t.leniere@student.tue.nl)