Work keeps piling up for David K. McKittrick.

Or, to put it another way, piling up keeps McKittrick and his company working.

Thanks to a French engineer-architect who couldn't keep his mind off his work even while vacationing on the beach, Reinforced Earth Co. of Rosslyn is able to offer an innovative technique for constructing retaining walls and bridge abutments.

The company claims that it has saved clients an estimated $70 million over the cost of standard construction, including $8.3 million on nearly 330,000 square feet of retaining walls erected along Interstate 66 in Northern Virginia.

Highway construction necessitates erecting retaining walls, those slabs of concrete that prevent hills of dirt from rolling down onto the roadway and the vehicles rolling along it. The general practice is to pour a thick concrete wall and, after the concrete has cured to the specified strength, to fill in with earth behind it.

Henri Vidal came up with a better way, according to McKittrick, who is the president of Reinforced Earth, a licensee of the Frenchman's technology.

Vidal was idly piling up sand on the beach at Ibiza, Spain, one day in the late 1950s, so the story goes, when he began to see if he could get a sand pile with sharply angled sides. He alternated layers of pine needles and sand, and found that this kept the sand from spreading out.

It took Vidal five years to translate this observation into a construction technique and to form a company called Terre Arm'ee, which is French for "reinforced earth."

Vidal came up with a system using galvanized steel strips to reinforce soil, which already has what is called compressive strength: You can set a large load on it and it will hold. The steel strips give the soil tensile strength, which is the ability to resist the pulling force illustrated by the soil's tendency to try to spread out when you stand on it. The strips resist this force through friction with the soil. They are attached to rows of interlocking precast concrete panels, taking the load off the wall formed by the panels.

Construction workers erect a row of panels, bolt strips to them, cover the strips with dirt and then add a new row of panels, followed by more strips and more dirt until the wall is finished. The result is a mosaic-like wall with a honeycomb pattern formed by the offset panels. The texture and color of the panels can be altered by various techniques when they are being cast.

McKittrick said in an interview that Vidal met with a positive response to his technique in France right from the start. "From my experience," McKittrick said, "the Europeans have been far more innovative and far more willing to accept new ideas in construction" than Americans. He said this probably is due in part to the scope of the devastation caused by World War II and the shortage of construction materials.

Vidal was mesmerized by the possibilities in the American market, but was able to generate only lukewarm interest in his technique from the Federal Highway Administration and large companies involved in construction contracting. So he ran a small advertisement in a trade publication, Engineering News Record, in September 1971.

"We Want Only One," the headline of the add proclaimed, and it went on to call for an experienced civil engineer to start a new company. McKittrick, who was vice president of a foundation construction company in Providence, R.I., at the time, answered the ad the same day that he read it. Vidal and associates came to Washington and interviewed McKittrick and five or six others of the 25 to 30 who had applied.

"Vidal is a very charming man--very creative," McKittrick said. But "what he laid out wasn't all that promising--starting a company from scratch." Vidal must be very persuasive, too, because McKittrick took the job. The company has expanded from a staff of two in 1972 to 30 in 1976 to 300 now, with offices in nine U.S. cities. "We grew very slowly," McKittrick recalled.

He pointed out that the company used no equity financing, only working-capital financing. There also are Reinforced Earth companies in Canada, Mexico, South America, Europe, the Middle East, Asia and the Far East.

Reinforced Earth doesn't build retaining walls--it sells contractors the necessary engineering and design drawings, instructions, superintendents, panels (or forms for panels) and steel strips. Some contracts specify that certain walls be erected using Reinforced Earth; others permit the contractor bidding on the job to choose the method of construction.

McKittrick claims that the Reinforced Earth technique offers a minimum savings of 10 to 15 percent over standard concrete walls, with the savings increasing one percentage point for every foot of height up to about 50 or 60 feet, which usually is the limit for standard walls.

The concrete panels can be used sooner after they are cast than poured-concrete retaining walls can because the panels have less load placed upon them, according to Robert A. Gladstone, Reinforced Earth's mid-Atlantic regional manager. This advantage and the absence of time-consuming, on-site concrete pouring means faster construction, Gladstone said.

He explained that the walls can be erected in all kinds of weather, and that crews erect Reinforced Earth walls and fill in behind them simultaneously--a faster process than pouring concrete, waiting for it to cure and then filling in behind the wall.

The Reinforced Earth technique also is being used to construct V-shaped bunkers and octagonal, inverted-cone structures to store materials such as coal. It was used for secondary containment dikes at the liquefied natural gas receiving terminal at Cove Point, Md. Reinforced Earth also is ready to use its technique for retaining walls for earth-sheltered housing in Vail, Colo. Its Architerra company is creating 12 units along a slope that varies from 40 to 60 degrees.