In the Changsha section of the railway, the teams dropped the original plan of a 10-km viaduct because that would require the demolition of a very large residential area there. Instead they successfully designed a tunnel below the Liuyang River, making this China's first underwater segment of the high-speed railway.

For Xu, there were many difficulties to be fixed in the task. He says when he couldn't fall asleep at night, he would drive his car along the Donghu Lake in Wuhan for inspiration.

"I would stop at a spot randomly and sit by the lake to think over the problems," Xu adds.

A lumbar disc protrusion he suffered shows how hard he had worked back then.

"He has endured great pain from the protrusion in recent years. Sometimes he needed our help to walk into a room. If it was so painful that he couldn't sit down, he would lean on the desk to check the design paper," says Guo Jianhu, 56, one of Xu's co-workers on the Wu-Guang railway project.

Such efforts paid off.