For Immediate Release
December 6, 2000

Coneheads at Work:
70-Year-Old Technology Gets New Life at Georgia Tech

Below the James River Bridge in Virginia, Georgia Tech engineers use a cone penetrometer contained in a special GeoStar truck to probe up to 40 meters into the ground to determine soil composition and load-bearing capacity. Computers on the truck receive data directly from the penetrometer's four sensors. Photo Courtesy of Paul Mayne (300-dpi JPEG version - 1,893k)

There are coneheads working in the Georgia Institute of Technology School of Civil and Environmental Engineering. No, not the pointy-headed extraterrestrials of "Saturday Night Live" fame, but Georgia Tech engineers with more down-to-Earth interests.

They take their nickname from a device called a cone penetrometer, which they use to ascertain the underlying stability and characteristics of a given parcel of land. The technique is actually some 70 years old, but it's getting a new look from these researchers.

Before the design of a major project such as a building, bridge or dam can begin, the ground underneath the proposed construction site must be tested to determine composition and other factors affecting its load-bearing capacity. The information helps engineers devise a foundation design to minimize settling and ensure the structure will stay in place.

In the United States, engineers prefer to gather this data by taking core samples. They use a drill to remove samples of earth at prescribed intervals and then bring them to the surface for study.In the 1930s, Dutch engineers devised a system using a sensor probe with a pointed or cone-shaped end. Pushed into the ground, the probe's sensors electronically relay information about certain ground characteristics to technicians on the surface. Though still widely used in the Netherlands, where below-sea-level topography makes ground conditions an ongoing concern, the cone penetrometer attracted few followers in the United States. Then about 20 years ago with advances in computer technology, the benefits of cone penetrometers finally began attracting notice in this country.

Paul W. Mayne, a professor in the School of Civil and Environmental Engineering's Geosystems Division, has traveled across the Southeast collecting subsurface data in his research for the National Science Foundation and the U.S. Geological Survey.

His cone penetrometer is contained in a special GeoStar truck that also contains machinery for pushing the probe up to 40 meters into the ground and computers for receiving data directly from its four sensors.

"We can measure pore water pressure, resistivity, dielectric properties and shear wave as the probe is pushed into the ground," Mayne says. "It's much faster than boring out samples, plus you get four readings on a continuous basis. With the old-fashioned way, you have only one number for every five feet or whatever interval you're extracting samples."

In addition to accuracy, the penetrometer technique is cleaner because no large hole is excavated ù the probe is a scant 36 millimeters in diameter. Also, measurements with a cone penetrometer cost about one-tenth of the price of the conventional method.

The basic penetrometer approach can be adapted to different applications, depending upon the properties the sensors are built to measure. Some devices provide information about ground chemistry, for instance, and are useful for environmental analysis of the subsurface. That particular use underscores the advantage of in-ground analysis because contaminated soil is not brought to the surface where it could cause further harm or, at the least, require costly containment steps.

While much of their work has been directed toward improved methods of evaluating cone penetrometer data, Mayne and his colleagues inventing new types of "cones."

"We developed a device that measures the flow of water into the probe, and from that we're trying to determine the permeability of the soil material, also known as the hydraulic conductivity," he explains. Another design provides 10 independent readings of soil characteristics.

"We're trying to optimize and maximize the number of measurements we can make," Mayne says. "The more information that can be collected, the more applications we can find that will benefit from its use."

RESEARCH NEWS AND PUBLICATIONS OFFICE
Georgia Institute of Technology
75 Fifth Street, N.W., Suite 100
Atlanta, Georgia 30308 USA

MEDIA RELATIONS CONTACTS:
John Toon (404-894-6986);
Internet: john.toon@edi.gatech.edu;
FAX: (404-894-4545)

Jane Sanders (404-894-2214);
Internet: jane.sanders@edi.gatech.edu

For more information, you may contact Paul W. Mayne, School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0355. (Telephone: 404-894-6226) (E-mail: pmayne@ce.gatech.edu)

WRITER: Gary Goettling, freelance writer