The Guinea Kindia Tunnel Project, constructed by China Railway 18th Bureau Group, successfully completed the breakthrough of ventilation shafts with diameters ranging from 3.5 meters and depths of 418 meters, 436.27 meters, 425.4 meters, 213 meters, 195 meters, 198 meters, 197 meters, to a final depth of 392 meters—using the Yier Technology AT-4000 L-Raise Boring Machine.

The achievement of this series of accomplishments not only highlights China Railway Eighteenth Bureau's outstanding construction capabilities but also underscores the formidable strength of Yier Technology's Raise Borer Machine in the field of tunneling equipment.

金迪亚隧道项目地处几内亚与塞拉利昂边境，地理位置偏僻，交通运输条件极差。恶劣的自然环境和艰苦的施工条件，对设备性能和售后服务提出了极高的要求。然而，Yier Technology凭借其先进的技术和优质的服务，成功应对了这些挑战。售后团队驻守，全流程服务保障张俊、彭帅、杨俊、李芝信四位售后工程师组成的精英团队，驻扎几内亚中铁十八局项目部，提供全流程现场服务。从设备安装调试、日常操作维护至现场操作施工，售后工程师团队全程参与，确保设备高效稳定运行。

During the equipment installation and commissioning phase, they leveraged their extensive experience and expert technical skills to meticulously inspect and fine-tune each component, ensuring that the equipment achieves optimal performance right from the start.

During daily operation and maintenance, they have developed a detailed maintenance plan, conducting comprehensive inspections and upkeep of equipment on a regular basis. This proactive approach ensures that potential issues are promptly identified and addressed, effectively preventing equipment failures from disrupting construction schedules.

During the on-site construction operations, the after-sales engineering team played an indispensable role. They not only closely monitored the equipment’s performance at all times, promptly adjusting parameters according to actual construction needs to ensure smooth operations, but also provided hands-on guidance and practical training, helping local Guinean after-sales personnel master the independent operation and usage skills of the AT-4000 Raise Borer Machine.

Efficient spare parts supply strengthens the construction support system.

Yier Technology has established a spare parts warehouse in Guinea for wear-and-tear components of its Raise Borer Machines, providing comprehensive support to ensure the smooth progress of the Kindia Tunnel project. Inside the warehouse, various spare parts are neatly organized and stored—ranging from critical mechanical components to easily worn items such as cutter picks, drill bits, seals, and filter elements, covering every need. In their daily operations, Yier Technology’s after-sales team stationed in Guinea regularly inspects and maintains the inventory, ensuring the quality and performance of all spare parts. At the same time, they maintain close communication with technical experts at Yier Technology’s headquarters and the company’s parts sales team, staying updated on equipment usage patterns and evolving spare parts demands, thereby offering expert advice on inventory management and procurement decisions.

Deep-well deviation-control technology ensures precise ventilation shaft alignment.

In the Kindia Tunnel project, constructing the ultra-deep shaft has proven to be a dual test of both technology and endurance. When tackling shafts exceeding 400 meters in depth, conventional construction methods often struggle to maintain the precision of the pilot hole. And once the pilot hole deviates from the intended path, subsequent expansion work becomes incredibly challenging—potentially even leading to the failure of the entire shaft-construction process.

Yier Technology's technical team fully understands the severity of this challenge. Leveraging their deep-rooted technical expertise and a relentless spirit of innovation, they have developed and successfully implemented cutting-edge deep-well deviation-control technology. This advanced system utilizes a high-precision guidance mechanism to continuously monitor the drill bit's position and orientation within the wellbore in real time. Whenever a deviation is detected, the system instantly issues corrective commands, automatically adjusting the drill bit's trajectory. In actual drilling operations, this technology has proven highly effective, ensuring that the pilot holes for all seven completed wells achieved unprecedented accuracy—laying a solid foundation for the subsequent reaming processes.

During the reaming process, we once again encountered the "roadblock" of the fractured zone. The rock structure in the fractured zone is loose and highly unstable, making it extremely prone to issues such as borehole collapse and drill bit jamming during reaming—problems that severely impact both construction progress and the quality of the final borehole.

Considering the characteristics of the fractured zone, a special design and optimization were carried out on the reaming cutterhead, adjusting the arrangement and angles of the roller cutters to better match the rock properties of the fractured zone. Meanwhile, they also refined the reaming process parameters, carefully controlling the drilling speed and pressure to ensure smooth and efficient reaming operations when passing through the fractured area.

Through relentless efforts and the adoption of deep-well anti-deviation technology along with an optimized reaming process, the project not only successfully traversed the fractured zone but also achieved outstanding borehole quality. The inner wall of the shaft is smooth and the diameter remains perfectly uniform—fully meeting the design specifications—and providing a reliable foundation for subsequent operations such as tunnel excavation and ventilation.