Ice Road Truckers

I have been watching a show on the History Channel, "Ice Road Truckers." The show is about tuckers that drive 10 to 50 tonnes loads across the frozen Arctic ice shield and the dangers associated with that job. When I was stationed at Ft. Wainwright, AK (I was with 47th Engineer Company) we did ice bridging for the military exercises that were held in Alaska. To create an ice bridge a suitable location had to be found, and then holes were cut into the ice, in these holes water pumps were inserted so that water could be blown on the ice thus building up the thickness of the ice. To cross an D7 Cat the ice had to ( I do not remember exactly) 22 or 28 inches thick where the Ice Road Truckers are crossing on 54 or more inches of ice with their loads. What I found interesting was that when the 18 wheelers were crossing the ice with the heavy loads a pressure wave is created under the ice and if two waves meet from opposite directions the result is broken ice and trucks in the water, freezing water, so when heavy loads are travelling from opposite directions one side has to pull over and stop and let the other trucks pass.