TAIYUAN -- A company in China's coal province of Shanxi has exploited coal under a railway tunnel using a new technology, the first project of its kind in the country.

From January to September 2017, 736,000 tonnes of coal was successfully excavated from under a 2-km-long cargo railway tunnel for coal transport in Yangquan city.

"The maximum land subsidence spot of the tunnel was only 81 mm after the exploitation, which did not affect train operations at all," Li Tao, a technical manager with the geological department of Yangquan coal industry group, told Xinhua Wednesday.

The technology was co-developed by the group and China University of Mining and Technology, and the exploitation was conducted by Pingshang Coal Mine, an affiliated company of the group.

"Via a hole drilled at the ground surface, concrete was filled into the cover rock, or the rock formation layer above the coal bed, to form a compacted platform to support the above weight so that the ground surface would not fall down during or after the mining," Li said. "We drilled seven holes and set up 43 monitor spots inside and outside the tunnel to monitor the ground sinking status, proving the technology works."

The technology can also be used for coal mining under buildings and water.

The group has around 2 billion tonnes of coal under buildings, water and railways, and the technology will help with exploitation.

A coal field of another affiliated company of the group is home to the households of 70 villages, making coal exploitation hard in the region as the company cannot afford the relocation expenses, according to Wang.

"Now that we have the technology, we are planning to excavate coal from under two villages this year, without relocating local residents," he said.

Shanxi is a vital energy base. By the end of 2015, the province had 270.9 billion tonnes of known coal reserves, accounting for 17.3 percent of the country's total.