Building Blocks, Army Style

April 1, 2000

Toward the beginning of my career in engineering, I worked at a company that had a sign on the wall that perfectly describes the plight of both the engineer and the erosion control technician: “It should be the objective of every dedicated company employee to anticipate potential problems before they arise, develop solutions to those problems without being asked to do so, and move quickly and efficiently to enact those solutions when called upon. However, when you’re up to your butt in alligators, it is often difficult to remember that your initial objective was to drain the swamp!” So we’ve found a piece of erosion control technology for you to add to your arsenal that you can use the next time your up to your butt in those proverbial alligators.

Interlocking paving blocks are not entirely a new technology. But like most equipment in the world, if you can improve on something enough, you can also get a patent on it. On April 6, 1999, inventor James R. Leech of Vicksburg, MS, received US Patent No. 5,890,836 for his new development of “Interlocking Blocks for Stream Erosion Control” (see Figures 1-4). The patent is assigned to the United States of America as represented by the Secretary of the Army in Washington, DC, but that doesn’t preclude you from using the technology. Granted, for commercial purposes you’ll have to get a license to use them and probably pay some sort of royalty for the use, but there is an exception depending on where or for whom you might be using this technology. The invention described herein may be manufactured, licensed, and used by or for governmental purposes without the payment of any royalties thereon. So if you’re working on a federal government project, then you can make or use this without any additional costs.

The invention is an interlocking paver that uses a dovetail locking mechanism and a center opening. Despite the appearance that these blocks would only work on flat surfaces, they are designed for the stabilization of stream and river banks and coastlines, roadbed embankments, and boat ramps.

So what’s the hole in the center for? This feature is designed to give the blocks a high proportion of open area. Open areas at the center of the blocks and between adjacent blocks serve two purposes: (1) to minimize the lift created by flowing stream or river water or by rainwater runoff, tending to disrupt the assembly of interlocking blocks placed on a sloping surface and (2) to provide openings within which the root systems of small plants can develop, thereby allowing the growth of vegetation to provide protection against the washing away of sand and silt by the action of moving water. The hole’s shape is not critical; however, a generally circular shape is preferred. The major dimensions of the central opening range from roughly 25% to 40% of the diameter of the block.

An additional feature of the invention is the use of a layer of filter-cloth material. The filter cloth is laid on the sloping surface, and the blocks are then placed on it. The filter cloth slows down the leaching of water through the open areas between the interlocking blocks and prevents the washing away of sand and silt by stream or river water or by rainwater runoff.

The dovetail projections and recesses are alternately provided at regular angular intervals of 90º, such that the blocks can be assembled in a square pattern. Projecting members of each block are provided 180º apart, and likewise the recesses are provided 180º apart and offset with respect to the projections by 90º. Interlocking connections between adjacent blocks are made simply by sliding the male and female dovetails together.

The blocks are flat, circular discs made of cement or fired clay and placed on the filter cloth in a square or equilateral triangular pattern. Sections of several blocks may be preassembled by being tied together with steel bars, such as concrete reinforcing bars, hooked to eye hooks in the cement blocks or with steel wire rope hooked to eye hooks.

The interlocking erosion control blocks are flat, circular discs with diameters ranging from about 8 to 24 in. and a height ranging from about 3 to 6 in. A diameter of approximately 16 in. and a height of about 4 in. are the preferred size.

In another style of the pavers, the blocks may have alternating projecting members and recess at 60º intervals. Such blocks may be assembled into a system of interlocking blocks, as shown here, where these are on equilateral triangular centers. Although, according to the patent, the square pattern is generally preferred over the equilateral triangular pattern because it provides more open space between blocks for the growth of vegetation.

If you think you would like to use this technology for nongovernment-related projects, you’ll need to obtain permission, probably in the form of a license, from the US Army. If you haven’t had previous contract dealings with the military, it can be a daunting chore at first, but Erosion Control can help set you in the right direction.

Army-owned technologies are controlled by the Army Research Laboratory Domestic Technology Transfer (DTT) program. DTT is a congressionally mandated program operated under the Army Research Laboratory (ARL) that promotes the transfer of army-developed technology and expertise to industry and academia. This growing program offers a wealth of opportunities for the private sector to exploit. The purpose is to make army technology available to the nonfederal sectors in order to improve America’s competitiveness, spur economic growth, and create more manufacturing and high-technology jobs.

There are several “mechanisms” in place for doing business with the ARL, but for the purposes of this new invention, the only one that is important to us it the Patent License Agreement (PLA). A PLA is an agreement between a federal laboratory and a nonfederal organization that allows the nonfederal organization to enter into exclusive, partially exclusive, or nonexclusive licenses for the use of ARL-owned or ARL-assigned patent applications, patents, or other intellectual property.

For information, instructions, and materials such as forms and applications, you will need to contact the ARL DTT. Be sure to have the patent number, date of issue, inventor, and exact title of the patent on hand when you call. Keep in mind that this patent has not yet been listed in the database as an available technology, but that doesn’t mean that it isn’t available for licensing. Contact R. Michael Claffy, US Army Research Laboratory, AMSRL-TT-TA, 2800 Powder Mill Rd., Adelphi, MD 20783-1197; 301/394-3098 (ph); 301/394-5818; or [email protected] (e-mail).

Here is also another possible resource and contact that might help to nail down an army patent license agreement: The Technical Assistance and Technology Outreach portion of the Domestic Technology Transfer program makes ARL scientific and technical personnel available to state and local governments, economic development organizations, and academia. ARL personnel share their technical expertise with you to facilitate setting up focused technology transfer programs and to lay the foundation for helping private industry profit from ARL research and technology. For further information on ARL’s Technical Assistance and Technology Outreach Program, contact Norma Vaught, US Army Research Laboratory, AMSRL-TT-TA, 2800 Powder Mill Rd., Adelphi, MD 20783-1197; 301/394-2952 (ph); 301/394-5818 (fx); or [email protected] (e-mail).

If you still aren’t entirely certain how to proceed, or if you even should, you may want to contact the ARL DTT program manager for general information about ARL technology transfer: Rich Dimmick, US Army Research Laboratory, AMSRL-CS-TT, Bldg. 434, Aberdeen Proving Grounds, MD 21005-5423; 410/278-6955 (ph); 410/278-5820 (fx); or [email protected] (e-mail).

About the Author

Paul Campbell

Paul Campbell is a technology columnist, an author, and a mechanical designer.