Recently, good news came from the KS project of the Xinjiang EH engineering project. The domestically produced first open-type + single-shield multifunctional dual-mode TBM, jointly developed by CRCHI and China Railway 19th Bureau Group, has successfully tunneled, becoming the first successful application case of this type of dual-mode TBM in this field. The successful application of this case will bring new breakthroughs to TBM design for plateau railways.

Equipment assembly and commissioning at the site

It is reported that the geological conditions in the project section are extremely harsh, with Class IV to V surrounding rock accounting for as much as 85%, mainly carbonaceous shale and carbonaceous siltstone, with poor integrity and severe softening upon contact with water. In the early stage of TBM tunneling, serious problems such as machine jamming were encountered. The initial 1.5 kilometers of the subsequent section consists of continuous Class V carbonaceous siltstone, making it even more difficult for a conventional open-type TBM to pass through.

After multiple discussions and joint efforts by the project owner, industry experts, the design institute, China Railway 19th Bureau Group, CRCHI and other units, the TBM was customized and upgraded before launching in the subsequent section. It was equipped with systems for auxiliary thrusting, steel segment assembly, muck conditioning, and advance reinforcement, and a single-shield mode was added to specifically enhance the equipment's ability to extricate itself. Thus, the domestically produced first open-type + single-shield multifunctional dual-mode TBM was developed. Under Class IV to V broken surrounding rock, the single-shield mode was adopted with steel segment assembly, achieving a monthly advance of 284 meters. Once the surrounding rock improved, it could directly revert to open-type TBM mode without modification, using shotcrete and rock bolt support, thereby reducing construction costs.

TBM tunneling site

The TBM completed its upgrade at the end of May 2021 and was launched in June. Starting in mid-July, it operated stably in single-shield mode, maintaining a stable daily advance of 9 to 11 meters even in extremely broken rock strata, with a monthly advance more than four times the original, initially achieving the expected goal.

The successful application of this technology further leverages the safe and efficient performance of TBM equipment, expands the application range of open-type TBMs, provides strong guarantees for open-type TBMs passing through unfavorable strata such as strong rockbursts and long, large broken zones, and offers strong technical support for TBM design for plateau railways.

TBM construction tunnels for plateau railways are characterized by large burial depth, high in-situ stress, high rock strength, and long tunneling distances. When TBMs pass through unfavorable strata such as strong rockbursts, long, large broken zones, alteration zones, and mud and water inrushes, CRCHI fully considered the construction difficulties of the project during design and carried out innovative design on conventional open-type TBMs, designing a dual-mode open-type TBM with multiple functions to overcome the complex geological construction risks of plateau railway TBMs.

As more major projects with complex geological conditions are launched at home and abroad, multi-mode TBMs will surely become the first choice for tunnel construction. CRCHI's pioneering breakthrough in this field will inevitably lead the industry in a new direction.

CRCHI DZ308 open-type TBM single-head tunneling (without maintenance adit) exceeds 17 kilometers

In addition, the project uses a cluster of 18 TBMs and 3 shield machines for construction, of which CRCHI produced 13 TBMs and 3 shield machines. On January 28 this year, in the KSTBM5 section of the same project, CRCHI's DZ308 open-type TBM achieved single-head tunneling (without maintenance adit) exceeding 17 kilometers, setting a record at the time for the longest single-head tunneling distance among similar domestic products.

As of August 20, CRCHI's 16 pieces of equipment in the project had cumulatively tunneled 178 kilometers. Among them, the SSTBM1 section of China Railway 18th Bureau Group achieved full breakthrough, with cumulative tunneling of approximately 20.541 kilometers, a maximum monthly advance of 1,280 meters, and an average monthly advance of 720 meters; of the 3 shield machines in the Shuang-San V section of China Railway 14th Bureau Group, 2 have achieved full breakthrough, and the other shield machine has already tunneled 10.37 kilometers in a single head. After breakthrough (tunneling 12.43 kilometers), it will become the shield machine with the longest single-head tunneling distance in the world.