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|Federal Highway Administration > Publications > Public Roads > Vol. 62· No. 1 > Computer Bits Give Geotechnical Drilling Cutting-Edge Technology|
Computer Bits Give Geotechnical Drilling Cutting-Edge Technology
by Richard J. Barrows and Stephen Hay
The Geotechnical Business-Focused Team (BFT) of the Western Federal Lands Highway Division (WFLHD) required a process for collecting data during geotechnical subsurface explorations that was easier and faster than the handwritten borehole logging (recording) system currently being used by WFLHD.
The team set out to develop a system that would increase the efficiency of borehole logging, eliminate soil and rock classification errors, and provide a method for rapid data transport from the field to the WFLHD office. The focus was primarily on phasing out handwritten borehole logging and implementing a procedure for electronic borehole logging.
Most of the roadway projects that WFLHD designs and constructs require a drill program to characterize the subsurface conditions. Typically, projects are located in remote, rugged terrain with extreme variability in weather conditions. Depending on the scope of the project, several exploratory boreholes are made with a drill rig. Drilling comprises a series of core or auger runs that are generally 1.52 meters (5 feet) in depth. Each run retrieves core samples or drill cuttings, which are visually inspected and compiled into boring logs based on a system of soil and rock classifications and interpretation. In addition to core and auger runs, standard penetration testing is often performed. These samples are classified using the unified soil classification system.
Before November 1995, each soil and rock classification report was manually drafted by a drill inspector, edited by the project geotechnical engineer, and typed by a technician before placement in a final geotechnical report. Needless to say, these final logs took several days to a few weeks to complete because staff time was constrained during the editing and redrafting phase of this project. In addition, the boring logs where subject to human error and to inconsistencies in soil and rock classification from one drill inspector to the next.
The Geotechnical BFT worked with the WFLHD Technology Development Team to obtain funding to develop an automated borehole logging system. The goals were to eliminate the costs of producing, tracking, and reentering information currently collected on paper forms; to improve quality control; and to develop a system that was user-friendly, rugged, weatherproof, and field-portable. Desired characteristics included pop-up soil and rock classification menus, accurate calculations, the capability to log in English and metric units, rapid off-loading of electronic forms, less effort, and increased quality.
During 1995 and 1996, WFLHD began evaluating a hand-held personal digital assistant (PDA). This PDA allowed the user to enter information using a hard-tipped, plastic pen capable of writing directly on the screen. This unit transferred written letters to type and automatically saved the information. Data could also be entered by typing on a built-in, pop-up, soft keyboard that placed typed text on the screen. In 1996, WFLHD awarded a contract to GAIA Software Inc. in Portland, Ore., to develop a software package based on a geotechnical format specified by WFLHD.
Testing continued in late 1996 and early 1997, and weatherproofing and overall protection of the device were addressed. The drillers were most concerned about this phase because they do not stop drilling in bad weather and did not want to have to build special enclosures to protect the borehole logging computer equipment. The Geotechnical BFT purchased a ruggedized PDA that was designed to be extremely durable and, best of all, waterproof. During testing, WFLHD drill personnel promptly discovered a design flaw with the ruggedized PDA's waterproof case when it filled with water. Needless to say, the PDA stopped working. The manufacturer revised the production process and provided the team with a new unit. The drill personnel took up where they left off and began drop testing the ruggedized PDA. It survived!
Field testing was done with the standard and ruggedized PDA units at Prince of Wales Island, Alaska; Glacier National Park, Mont.; and Spokane Indian Reservation, Wash. These locations proved to be ideal for testing because they collectively provided a variety of weather and drilling conditions. Once mastered, the handwriting recognition features of the PDAs were swift and reliable, and the need for paper boring logs diminished. By the time testing was completed, several software modifications and hardware reconfigurations were implemented, and the system evolved into a form suitable for standard production.
The ruggedized PDA proved itself by standing up to the unusually wet El Nino-induced snows of early 1998 without missing a beat.
The automated system is more efficient and eliminates the classification inconsistencies encountered with manual logging. This system allows the storage of large quantities of borehole data. The manual method required the drill inspector to keep sheets of boring logs organized, and data was transferred by facsimile or mail to the WFLHD office. With the automated system, the user can transfer information to back-up storage cards. In addition, the electronic boring logs can be transferred to the WFLHD office via Internet e-mail. It is a remarkable feat that with the touch of a plastic pen, the PDA dials and sends data over the Internet with all the authority of a full-size Pentium personal computer. During data transfer, logs are directly imported into the WFLHD computer system and are processed into a final borehole log format. What previously took days or weeks can now be done in a matter of minutes.
As the automated method of borehole logging becomes more widespread, we expect additional software and hardware refinements.
Richard J. Barrows, P.E., is a geotechnical engineer in WFLHD. He has worked for the Federal Lands Office for six and a half years. He has a bachelor's degree in civil engineering and a masters degree in geotechnical engineering from Portland State University. He is a licensed engineer in the state of Oregon.
Stephen Hay is a staff geologist for Geoengineers Inc. of Beaverton Ore. During the development of the automated borehole logging system, he was a temporary employee of WFLHD. He has a bachelor's degree in geology from Portland State University.
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