Construction tool helps Egyptologist unlock pyramid tunnel

A device construction workers typically use to measure the thickness of concrete helped archaeologists and millions of television viewers glimpse inside a blocked chamber in Egypt’s 4,500-year-old Great Pyramid.

The pyramid’s mystery deepened Sept. 17 when a robot drilled through a chunk of limestone blocking an 8-inch-by-8-inch shaft only to reveal another door.

A handheld concrete thickness gauge made by Colorado-based Olson Instruments was attached to the robot and measured the limestone wall’s thickness and penetrability to make sure the robot could drill through it without damaging the ancient structure.

The two-hour expedition was broadcast live from the Giza Plateau in a production titled National Geographic Channel Presents Pyramids Live: Secret Chambers Revealed.

Olson Instruments’ concrete thickness gauge — called CTG-1 — told the excavation crew, which was operating the device via a cable snaked 213 feet through the tiny shaft, the exact thickness of the limestone door – 3 inches. The crew then used iRobot’s Pyramid Rover to drill through the stone.

“It was right,” Cathy Szilagyi, operations manager at Olson Instruments, said of the CTG-1’s measurement. “They knew exactly how far they needed to drill because they didn’t want to affect the integrity of the pyramid.”

Szilagyi said engineers at iRobot — a company founded in 1990 by several leaders in the field of artificial intelligence – laughed when she called to congratulate them after the expedition turned up another door.

But Eqyptologist Zahi Hawass, who led the excavation, was not disappointed with the discovery.

“We can see another sealed door,” he shouted when a camera showed pictures from the other side of the limestone block for the first time. “It looks to me like it is sealing something. It seems that something important is hidden there.

“This is one of the first major discoveries in the Great Pyramid in some 130 years, and now what we need is time for further analysis.”

Szilagyi said the robot couldn’t proceed through the next door immediately because the details of every excavation inside the pyramids have to be approved ahead of time by the Egyptian government. The Egyptians are very protective of their historical structures and artifacts, she said.

Szilagyi said she does expect iRobot to venture back inside the mysterious shaft eventually and feels confident the CTG-1 will be included in the journey. But she said many more expeditions might be needed to discover what’s hidden at the end of the shaft.

“This could go on for a long time,” Szilagyi said. “There could be door after door after door. No one knows.”

The excavation crew set up camp in an empty chamber of the pyramid during the expedition. Two small shafts lead out of the chamber, and archaeologists aren’t sure why the ancient Eqyptians built the tiny tunnels, which are unique to pyramids erected from 2575 to 2150 B.C. One theory is they were constructed as passageways for the pharaoh’s journey to the afterlife.

The CTG-1 is about 2 years old, and uses an impact echo to measure thickness and detect flaws in concrete structures such as bridges, highways, tunnels and walls. The nondestructive CTG-1 is 3 inches by 5 inches and measures concrete thickness up to 18 inches.

For more information about the CTG-1 and the National Geographic expedition inside the Great Pyramid, click the links in the right-hand column.