Camera pulls workers out of the hole
One of the most dangerous jobs on a construction site is inspecting the foundation or pier holes — also known as shafts. In 2004, safety concerns prompted the Missouri Department of Transportation to implement a rule requiring inspections on state highway projects be done without sending a person into the shaft.
To the engineers at one local company, that rule meant an opportunity to introduce technology that they hope will eventually eliminate in-person shaft inspections in all construction projects.
GALLERY: Photos of spyball in actionMaryland Heights-based Geotechnology Inc. uses a camera meant for underwater exploration and observation to inspect shafts. The camera can take full-color video which can be streamed live to a computer on-site or recorded for later viewing. It also have a 360-degree pan, tilt and a zoom lens capable of focusing in on specific areas of the shaft.
All that means a safer work environment, said Phil Jozwiak, vice president for transportation and infrastructure at Geotechnology.
"Sending people down the shaft in such confined space … it’s risky," Jozwiak said. "You have to be in a harness, sometimes you have wear a respiratory device, there may be methane coming out of the hole."
Using a camera and pre-drilling probe holes also save time, Jozwiak said.
There are two ways a shaft is drilled and inspected. The first is when a contractor drills a shaft, it is cleaned out and another pilot hole, several feet deep, is dug at the bottom of the shaft to inspect the rock surface beneath it. If the rock is not strong enough, the shaft is dug deeper till a solid rock surface is found. And finally, someone is harnessed, equipped with safety gear and sent into the shaft to inspect it.
What they are looking for is clay seams or any anomalies in the rock surface that may indicate a weak spot, Jozwiak said.
The other method involves drilling a probe hole about two-inches wide and removing the rock core first cash advance. The core is then examined to determine if the location is strong enough and how deep the shaft needs to be dug, he said.
Then the shaft is drilled, and instead of a person, the camera is lowered into the hole. It is safer, more efficient and time-saving, Jozwiak said.
It’s also handy in situations where a bridge needs to be built over a stream or river. Shafts dug underwater cannot be examined without stopping the water flow and emptying the hole if they have to be inspected in person.
The camera is submersible and can be used as long as the water is not too murky, he said.
It is portable and lightweight and only needs one person to operate. Some of the other cameras in use have to be lowered from a drill rig or a crane or mounted at the rear of a vehicle, said Craig Kaibel, staff engineer for Geotechnology.
But Kaibel also found a few flaws in the system, one of them was stability.
Initially, engineers lowered the camera into the shaft on two cables, he said. But if it was zoomed or tilted rapidly, the camera started rocking back and forth on the cable.
"Looking at a rocking image would make you seasick," Kaibel said. "I took it out once and decided it wasn’t good enough."
It also was difficult to have the camera centered in the shaft to get a clear view of all sides.
Kaibel decided to make a few changes.
He created a light-weight steel frame that can be mounted at the top of a drill shaft and used to lower the camera into the shaft. He also attached a centralizer to the camera which keeps it in the center of the shaft and can be adjusted for a diameter of 12 inches to five feet.
Now when the camera moves, the movement is restricted by the centralizer and the image stays stable, Kaibel said.
The toughest challenge now is to convince more contractors and developers in the private sector to start using the camera as an alternative to sending someone to inspect the shaft, Jozwiak said.
"Everything is going in the direction of greater safety," Jozwiak said. "Some larger projects are already starting to use it. Pit is a matter of getting engineers and owners comfortable with it."