On July 2, a water diversion tunnel in northwest China constructed by China Railway 18th Bureau Group was holed through 9 months ahead of schedule. It is the first section among 18 TBMs along the project to achieve breakthrough, and the first time a domestic TBM has bored continuously for over 20 km, with monthly advance exceeding 1,000 m for three consecutive months. At the same time, it overcame both soft and hard rock, crossed fractured zones, and achieved large burial depth and long-distance boring, setting high-production records of a maximum daily advance of 56.61 m, a maximum monthly advance of 1,280 m, and an average monthly advance of 720 m for the whole section. “Continuous, balanced and fast” boring is of vital significance to achieving the project goal of “boring through.”

　　The section has a burial depth of 245 m, with Class II and III surrounding rock accounting for 81.62%, of which the maximum saturated compressive strength of rock is 154 MPa, and rock greater than 80 MPa accounts for about 35%, with an average monthly advance of 902.46 m; Class IV surrounding rock accounts for 16.7%, with an average monthly advance of 511.36 m.


　　The tunnel in this section has a total length of 21.031 km, including 9,971 m in the TBM1-1 section and 10,570 m in the TBM1-2 section. An open-type full-face rock tunnel boring machine (TBM) and a continuous belt conveyor from CRCHI were used for blind-end boring of 20.551 km, with an excavation diameter of 5.53 m, total installed power of 3,500 kW, total machine weight of 1,100 t, and total length of 215 m.


　　Launch: a rough road ahead
　　2017

　　The Gobi desert has complex geological conditions and a harsh natural environment. This section required boring more than 18 km under relatively high rock strength, placing high demands on the equipment's support performance and reliability. The TBM entered the site on July 23, 2017, completed assembly and commissioning on September 14, 2017, and officially began boring on September 25, 2017.


　　Boring: outstanding performance
　　2018

　　During tunnel construction, various complex construction difficulties were encountered, such as broken surrounding rock, collapse, and rapid geological changes, and some strata had seepage, dripping and flowing water. Facing these difficulties, the CRCHI TBM still forged ahead, setting high-production records of a maximum daily advance of 56.61 m, a maximum monthly advance of 1,280 m, and an average monthly advance of 720 m for the whole section. The TBM's average utilization rate was 39.62%, and the average equipment availability was 94.6%. Monthly advance exceeded 1,000 m many times, setting the highest construction record for TBMs in tunnels of the same type, winning high recognition and praise from the owner and setting a benchmark for other projects under construction.


　　Breakthrough: CRCHI speed
　　2018

　　At 10:18 on October 12, 2018, the first phase of the tunnel was successfully holed through 200 days ahead of schedule. During this period, all equipment operated normally.

　　Since the start of construction, the project department encountered various complex construction difficulties during tunnel construction, such as broken surrounding rock, collapse, and rapid geological changes. In the first phase of the tunnel, relying on the CRCHI TBM, high-production records were still achieved: an average daily advance of 25.4 m/day, a maximum daily advance of 56.6 m/day, a maximum single-shift advance of 30.31 m, a maximum monthly advance of 1,280 m, and an average monthly advance of 830 m.

　　On October 13, 2018, the TBM prepared for the second phase of boring, and on March 24, 2019, it completed the relocation tasks for TBM stepping, the continuous belt conveyor, and ventilation, water and power.


　　The tunnel's breakthrough 9 months ahead of schedule and the outstanding performance of the CRCHI TBM once again demonstrated the amazing “CRCHI speed,” presenting a gift for the Party's 99th birthday.

　　At the same time, on July 2, 2020, the TBM1-2 section was successfully and smoothly holed through, marking the early breakthrough of the project's first TBM-constructed tunnel. This phase took 466 days to complete the 10,570 m boring task, with an average monthly advance of 700 m and a maximum monthly advance of 1,000.04 m.
　　The three magic weapons of “CRCHI speed”


　　Weapon 1

　　Meticulous organization by the construction unit and efficient construction

　　In response to various complex construction difficulties encountered during construction, such as broken surrounding rock, collapse, and rapid geological changes, China Railway 18th Bureau Group consulted with multiple parties and continuously optimized the construction plan. At the same time, it strengthened the training and learning of technical personnel, kept real-time command of new TBM technologies and methods, and laid a solid foundation for boring work.


　　Weapon 2

　　Stable equipment quality, behold our CRCHI sharp tool

　　The open-type TBM independently designed and manufactured by CRCHI features targeted designs for the cutterhead, main drive, support system, drainage, and more. The equipment's excavation system, control system and support system are reasonably designed. All systems of the equipment operate stably, the design parameters meet construction requirements, and equipment performance and availability have reached the international advanced level.


　　Weapon 3

　　In-place service, escorting you all the way

　　Starting from trial boring on September 15, 2017, CRCHI dispatched a professional team to provide full escort services to ensure the normal operation of the equipment and construction progress. During CRCHI's escort, the equipment operated stably, and construction progress exceeded 1,000 m for three consecutive months. The services provided by CRCHI were thoughtful and meticulous, striving for perfection, and the service team was experienced and highly skilled. From equipment launch to breakthrough, CRCHI received a total of 2 letters of commendation and 2 banners from the customer, gaining full recognition from the customer.