An expressway in Northwest China which cost 8.7 billion yuan ($1.4 billion) has been struck by subsidence again just one year after it opened to traffic, China Youth Daily reported Friday.

"Tianding Expressway must be the worst one in China. Despite the road surface subsidence, rat-holes-like cavity dot the road," complained Zhang Jun, a lawyer in Northwest China's Gansu province on his micro blog in July.

Heavy rain has saturated supportive slopes, causing the subsidence, said Tan Yingpeng, engineering division chief of Gansu transport department.

Tianding is not the only expressway affected by the persistent rainfall, according to Tan. His statement is supported by statistics released by Gansu transport department which says a number of other national highways also suffered due to the heavy rain in Gansu province.

This is not the first time the 235-kilometer long Tianding Expressway has drawn public criticism for subsidence. Not long after it opened to traffic in 2011, subsidence struck the poorly built highway and drivers have called it "jelly-built" since.

Despite local authorities ordering an in-depth investigation into the cause of the subsidence following public pressure, one year on, the results have still not been published.