Print this page Procedures for Soil Sampling in Borings
John Poullain, P.E.
Course Outline
This three hour online course discusses the commonly used equipment and procedures for undisturbed and disturbed soil sampling in borings and methods for sampling and recovering soil samples. Visual examination 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 augers, rotating wash, bucket augers and hand auger boring. Guidelines for a wide variety of samplers including split barrel, thin wall tubes, continuous push, pitcher tube and continuous soil auger are discussed as well as the storage, handling and selection of specimen samples. Basic soil types and factors such as the groundwater table are considered in the selection of appropriate drilling and sampling methods.
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:
- Understand the advantages and limitations of various drilling methods and the most suitable use of drilling equipment for soil formations and groundwater conditions encountered;
- Be familiar with usage of drilling fluid, the types of soil formations and the groundwater conditions requiring drilling fluids;
- Be knowledgeable about certain precautions and procedures required for obtaining and proper handling and storing of soil samples;
- Understand the basic operation and parameters of boring and sampling equipment. Photographs show the drilling equipment and type of samplers;
- Understand how undisturbed samples are obtained and when specialized procedures are required;
- Be familiar with how disturbed samples are obtained and how disturbed and undisturbed sampling differ;
- Understand the advancement of the borehole with methods such as rotary drilling, augers, displacement or percussion;
- Understand the methods used to stabilize and clean the borehole before sampling; and
- Consider the importance of visual observations and information of soil conditions that are available during drilling operations.
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 soil strength; soil characteristics and consideration of problem soils and how soil behaves under imposed loads. Drilling and core samples provide the necessary samples for laboratory tests and for in-situ field-testing. It is important to follow the criteria and guidelines so the appropriate drilling methods are selected especially since subsurface exploration is expensive but not nearly as expensive as for a project failure.
Because of the large variety of soils and a large variety of 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.
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 (paragraphs 3.3 and 3.4), F-6 and F-8 of the US Army Corps of Engineers manual EM 1110-1-1804, “Geotechnical Investigations”, (2001 Edition, 37 pages), PDF file and the course paragraph “Course Introduction”.
The link to the documents are as follows:
US Army Corps of Engineers manual EM 1110-1-1804, “Geotechnical Investigations”, F-6
US Army Corps of Engineers manual EM 1110-1-1804, “Geotechnical Investigations”, F-8
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Course Summary
This course should serve as a guide for selecting proper drilling methods needed to determine the characteristics of subgrade soil formations in order to protect against potential settlement and ground movement. The advantages and limitation of soil drilling equipment, coring equipment and samplers are discussed and photographs are presented to understand the equipment. Basic soil types are discussed to understand the selection of soil drilling methods. The importance of following proper procedures for sampling is stressed and considers the proper storage, handling and selection of soil specimens for testing programs.
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.
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.
