Drilling and Sampling

Summary

Professor Kitch introduces geotechnical engineering webcasts focusing on soil drilling and sampling techniques. The presentation covers various drill rigs and methods like solid stem auger, hollow stem auger, wash boring, and casing methods. It explains how each technique operates, the types of soil they're suited for, and the process of obtaining and analyzing soil samples. Animations are used to illustrate subsurface activities, complementing photos and videos, and links to field operation videos are provided for further insight.

Takeaways

• 📚 Professor Kitch introduces a series of geotechnical engineering webcasts focusing on drilling and sampling techniques.
• 🔧 The presentation aims to complement visual materials by explaining what happens underground during drilling and sampling.
• 🚜 Different types of drill rigs are discussed, including large truck-mounted, off-road track-mounted, and trailer-mounted portable rigs, each suited for various site conditions.
• 🔩 The process of drilling involves positioning the rig, erecting the drilling boom, and using a drill head to apply torque and vertical thrust.
• ⚒️ The solid stem auger-open hole method is a simple technique using a continuous flight auger to bring soil cuttings to the surface, but it provides low-quality samples.
• 🧪 High-quality soil samples are collected by removing the auger and using a sampling tool, which is a hollow tube pushed into the soil to retrieve undisturbed samples.
• 🏗️ In stiff or dense soils, a heavy-walled sampler driven by a drop hammer is used instead of a push-type sampler.
• 🕳️ The hollow stem auger method is used in soils that cannot maintain an open hole, as it supports the hole with the auger stem while sampling.
• 💧 The rotary wash boring method uses a slurry or drilling mud to flush cuttings out of the hole, providing a quicker and deeper drilling method with added hydrostatic pressure for stability.
• 🛠️ The casing method involves driving a large diameter pipe into the ground to support the hole, allowing for sampling in unstable soil conditions.

Q & A

What is the main purpose of Professor Kitch's geotechnical engineering webcast?

The main purpose of the webcast is to provide an overview of common soil drilling and sampling techniques, supplementing presentations with animations to demonstrate what happens below the ground.

Why can't photos and videos of drilling and sampling operations show what is happening below ground?

Photos and videos can only show the equipment being used on the surface, but they cannot reveal the subsurface processes and interactions that occur during drilling and sampling.

What are the four most common drilling techniques mentioned in the presentation?

The four most common drilling techniques mentioned are: Solid stem auger-open hole method, Hollow stem auger method, Wash boring method, and the Casing method.

What types of drill rigs are commonly used in geotechnical engineering?

Commonly used drill rigs include large truck mounted rigs, off-road track mounted rigs, and trailer-mounted portable rigs.

How does the solid stem auger method with an open hole work?

In the solid stem auger method, a continuous flight auger with a cutting bit at the tip is rotated and pushed into the ground. The auger flights carry the loosened soil to the surface, and samples can be taken by replacing the auger bit with a sampling tool.

What are the limitations of the open hole method using a solid stem auger?

The open hole method is limited to situations where the soil is stiff or strong enough to remain open after the augers are removed. It is not suitable for soft soils or clean sands where the hole may squeeze or cave.

How does the hollow stem auger method differ from the solid stem auger method?

The hollow stem auger method uses a continuous flight auger with a retractable center bit. The auger remains in the ground to support the hole during sampling, allowing for the acquisition of samples through the hollow stem.

What is the rotary wash boring method, and how does it handle cuttings?

The rotary wash boring method uses a slurry or drilling mud to flush cuttings out of the hole. The mud is pumped down the drill stem, exits through the bit, and carries the cuttings to the surface, where they are separated from the mud in a holding tank.

What is the casing method, and how does it support the bore hole during sampling?

The casing method involves driving a large diameter pipe into the ground to support the hole. The hole is then cleaned using either auger or rotary wash methods, and samples can be taken from the undisturbed soil below the casing.

What factors influence the selection of a drilling method in geotechnical engineering?

The selection of a drilling method depends on factors such as the location and accessibility of the site, the type of project and its objectives, and the soil conditions.