China’s Northern Heavy Industries (NHI), part of Fangda Group and based in Shenyang, Liaoning Province, says it is creating a new era for the development of coal mining equipment in China with the use of tunnel boring machines (TBMs).

The Chinese group from 2016 to October 2019 also owned US-based The Robbins Company, itself well known for the successful application of TBMs in mining with examples including Stillwater platinum and palladium mine in Montana, USA; Anglo American’s Grosvenor coal mine in Australia and the Ok Tedi copper and gold mine in PNG.

China is rich in coal resources which are often located at significant depths with complicated geological conditions. The traditional drill and blast method or roadheader excavation is generally used in coal mine roadway tunnelling but which is faced with the disadvantages of slow progress, high cost, a poor working environment, sometimes dangerous conditions and poor tunnel forming.

NHI has been increasingly applying TBMs in China’s coal industry in recent years. In 2014, a TBM with a diameter of 4.53 m was developed for rock roadways in the Zhangji mine of Huainan Mining Group in Anhui Province. In 2015, it successfully advanced 2 km at a depth of 500 m underground. A new record in coal mine rock roadway construction was set, with the highest daily advance of 30.7 m and an average monthly advance of 404 m, the highest daily advance being 10 times higher than the traditional technologies, and the monthly advance 4.5 times higher.

A 6.33 m large-diameter full-section TBM for coal mine rock roadways was then successfully fabricated by NHI in April 2019. This machine was specially designed for Shandong Energy’s New Dragon coal mine in the Xinjulong mining area.

A TBM with a diameter of 4.53 m was delivered in December 2019 which was put into Xinyuan mine of Yangquan Coal Group with further design and construction improvements on the two previously delivered machines.

The latest TBMs from NHI referred to as semi-coal rock TBMs are able to change from cutting rock strata to half coal and half rock (often found where there is rock in development areas with many thin coal seams) where needed. In May 2020, one of these machines was delivered to the Zhaizhen coal mine of Xinwen Mining Group, also part of Shandong Energy. The “Xinwen One” full-section semi-coal rock TBM has now been commissioned and is in full operation. It is 60 m long and its 4-piece compound cutter disc has a diameter of 4.5 m.

NHI is the only heavy machinery manufacturing enterprise in the world that currently applies TBMs on a major scale to the construction of coal mine rock roadways. “The system of machines can be customised and designed according to the user’s requirements, such as mesh, arch frame, anchor rod, advance drilling, synchronous spray mixing [shotcreting] etc and a complete set of solutions can be provided for the special requirements of the project, such as well [shaft] transportation, site assembly, initial operation, disassembly, site transfer, etc.”

As an example, the shield and the excavated wall in the most recent NHI project at Zhaizhen are supported by a continuous row of steel bars without unsupported roof distance, so that the underground construction workers and electromechanical equipment are well protected. There are independent air outlets at the rear of the trailer and the tail of the main machine. The wind speed at the rear of the trailer was up to 0.5 m/s. There were independent dedusting and air extraction channels inside the cutterhead excavation bin and the main beam and dry dedusting system, which could effectively ensure fresh air, smooth ventilation and appropriate temperatures for the underground workers. In the process of rotary excavation by the cutterhead, the sprayed water mist could cover the entire excavation section, to effectively suppress the generation of dust and sparks.

The full-section TBM used for coal mine rock roadway designed and developed by NHI is with a capacity up to 5.4 m/h. Within 100 MPa rock, the average monthly advance of the full-section TBM with good surrounding rock integrity can be more than 1,000 m/mth. At the same time, it can also cope with the excavation of rock stratum up to 200 MPa, and still achieve 600 m/mth. Such working efficiency is 20 times that of traditional construction methods.