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Drill Rig Selection

John Poullain, P.E.


Course Outline

This three hour online course discusses the commonly used equipment and methods used for conventional drilling and sampling operations. The various type of drill rigs, drill bits, drive methods and equipment and apparatus such as casings used to drill and stabilize boreholes are presented. Factors that determine the selection of the drill rig such as type of subsurface materials, condition of rock, accessibility and water table are discussed. Visual observations and other measures used during drilling and sample recovery are considered. The types of equipment and drilling methods covered in the course include solid-stem, hollow-stem flight augers, hammer drills, rotating wash, churn drills, bucket augers and hand auger boring. Guidelines for sampling methods are discussed with brief coverage of sampling devices. Oil and gas well drill rigs are not covered here.

This course includes a multiple-choice quiz at the end, which is designed to enhance the understanding of the course materials.

Learning Objective

At the conclusion of this course, the student will:


Intended Audience

This course is intended for civil engineers and project engineers.


Course Introduction

The design of building foundations, roadways, excavation, fills and slopes requires an understanding of subsurface formation strength, characteristics and consideration of problem soils and how soil behaves under imposed loads. Drilling and core samples provide the necessary samples for in-situ field-testing and laboratory tests. It is important to follow the guidelines so the appropriate drilling methods are selected especially since subsurface exploration is expensive but not nearly as expensive as for a project to fail.

Because of the large variety of soils and applied soil mechanics problems there is also a large variety of soil and rock exploration and sampling methods for determining the engineering properties of soils. Before the boring program can be requested the design engineer must define the purpose for the exploration program and the testing program for his self and for field and laboratory personnel. Accurate observations and operations of the exploration equipment are of great importance and the equipment must be properly maintained, otherwise the sampling results will be valueless and result in poor design and construction.

Drill rigs are used for many purposes but all essentially bore holes in the ground. They are used to drill water wells, oil and gas wells, and to sample subsurface soil and rock formations. Drill rigs are used to perform subsurface construction such as utilities, tunnels, and cast in place piers. They can be mounted on trucks, trailers tractors, skids, and permanently mounted on land or marine-based platforms or piles. Drill rigs are classified by the power source, i.e. electric, hydraulic, pneumatic or mechanical, by the length of pipe, and methods of drilling, i.e. rotation and/or percussion. Drill types include auger, cable tool, direct push, hydraulic-rotary or percussion rotary drilling.

Not only must exploratory personnel be well trained and conscientious; the drilling and sampling equipment must also provide accurate samples and data for a variety of tests. Samples must be handled and stored with care following established standards. Samples should be inventoried, examined and tested as soon as they are received. Sometimes, especially for large testing programs, it may become necessary to store the samples for days or weeks, but no longer than 15 days If possible. If they are stored for a longer time the undisturbed samples should be protected against damage or changes in water content by maintaining at temperatures close to those required for the project. Rewaxing and relabeling may be required. Nevertheless the stored samples may undergo physical and chemical changes when stored too long no matter how carefully stored and resealed.

Soil particles are rearranged and densified to improve the soils’ engineering properties of strength, permeability and compressibility. The existing subgrade may have poor strength or instability due to excess clay, expansive clays, silts, fine sands, voids, collapsing soils or high watertables. The existing soil properties must be known to protect against potential settlement with the required bearing capacities. There are problem soils such as loess, hydraulic fills and tailings, which have collapsing or low-density structures, and when saturated have large decreases in volume and loss of strength. Other soils, which contain clays such as bentonite, can expand and increase in volume when exposed to water. Expansive soils however can shrink or decrease in volume when water is not present. There are also dispersive clays so named because the soil particles are not structurally sound and can easily disperse or detach and erode in still water.

Compaction or mechanical stabilization is one of the oldest means of soil stabilization.
Mechanical stabilization may achieve the desired results by blending two soils and/or mixing with admixtures. If suitable soil was located within a feasible haul distance, blending the soils together could effect an improvement in the existing soil. However the soil blending would introduce ROW, hauling and handling issues to consider. Using chemical or bitumen additives to improve a soil is another possibility but handling and excavation of the existing soil would also have to be considered.  Certain soils because of their chemical nature, organic or high acid compounds may not be responsive to these stabilization methods and may be corrosive to steel reinforcement. Often the soils are not readily distinguished by their classification or physical properties. Corrositivity and pH tests will determine the chemical and organic content of the soil if these are suspected problems.

 

Course Content

The course is based on Chapters F-3 and F-7 (pages F-7-5 to F-7-12) of the US Army Corps of Engineers manual EM 1110-1-1804, “Geotechnical Investigations”, (2001 Edition, 39 pages), PDF file and the course paragraph “Course Introduction”.

The link to the documents are as follows:

Chapter F-3 EM 1110-1-1804, “Geotechnical Investigations”

Chapter F-7 EM 1110-1-1804, “Geotechnical Investigations”

Terms

Please click on the above underlined hypertext to view, download or print the document for your study. Because of the large file size, we recommend that you first save the file to your computer by right clicking the mouse and choosing "Save Target As ...", and then open the file in Adobe Acrobat Reader. If you still experience any difficulty in downloading or opening this file, you may need to close some applications or reboot your computer to free up some memory.

Course Summary

This course should serve as a guide for selecting drilling rigs and provides an insight into the methods used to advance and stabilize boreholes. The advantages and limitations of soil drilling equipment, coring equipment and samplers are discussed with photographs presented to understand the equipment. Basic soil types are briefly introduced to understand the selection of drilling rigs and methods used for subsurface drilling. The importance of following proper procedures is stressed.


Related Links

For additional technical information related to this subject, please visit the following websites or web pages:

http://www.haywardbaker.com/
Information and applications describing construction methods for structural support and earth retention. Provides solution “tools” for problem soils and applications for projects.

http://www.usace.army.mil/publications/eng-manuals/em1110-2-1913/c-3.pdf
Describes lab tests for pervious and fine-grained cohesive soils and the soils characteristics tested for.

http://www.ggsd.com
Lists over 50 software packages, shareware or commercial as noted, for soil boring logs and subsurface profiling.

http://www.delmag.cc/index.php
Types of drilling rigs, attachments and techniques.

 

Quiz

Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.

DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.