Jiang Li from the School of Mechanical Engineering at the University of Science and Technology Beijing, Haosheng Chen at the State Key Laboratory of Tribology at Tsinghua University, and Howard A. Stone with the Department of Mechanical and Aerospace Engineering at Princeton University presented new evidence that the large stone monuments in China’s Forbidden City were transported on man-made ice roads in the Nov. 4, 2013, edition of the journal Proceedings of the National Academy of Sciences.
Li and Chen discovered one ancient document that described the transport of a 120-ton stone over an artificial ice path in the winter of 1557. The stone was moved 42 miles from its original site. The engineers and workers at the time used wells to supply liquid water to reduce the friction on the man-made ice road.
China developed the wheel around 1500 B.C. E. but the ice road method proved more efficient and required less man power.
The researchers calculated the stone could have been moved by 50 men in 28 days using water to lubricate the artificial ice road. Water reduces the coefficient of friction. The wells were spaced about one third of a mile apart to provide sufficient water to lubricate the sled that the stone rode on. The idea was to minimize labor and the potential for damage to the expensive and delicate stone. Cold weather conditions during the time in China facilitated this method.
Comparison with known and documented methods of moving large stone from ancient Egypt and modern times indicates that this was the preferred method of moving large stone monuments in China because wheeled vehicles posed too great a potential for damage.