At CRCHI, stories are never in short supply. These moving, unforgettable and interesting stories bloom like spring flowers in the brightly lit R&D center, in the roaring workshops, and on the technical service projects. Recently another story unfolded. Unlike the “protagonists” of past stories, this time the “Internet celebrity” is the “electro-hydraulic hybrid dual-drive technology” of CRCHI's hard rock tunnel boring machine (TBM).

At around 20:00 on March 10, the sun had just shyly hidden itself deep in the Tianshan Mountains, and construction at the Xinjiang ABH project was in full swing. Suddenly, a shrill ringing of the telephone broke the quiet of the project department office. “A TBM that is currently boring has encountered difficult challenges!” The incident happened suddenly. Due to worsening geological conditions at the construction site, the altered rock was soft, and much of the fine sand, after mixing with groundwater, became highly adhesive and flow-plastic, causing a collapse of the cutterhead face. The TBM cutterhead was wrapped up, the construction site was shut down, and the situation was urgent.

As is well known, the unknown underground space and ever-changing geological conditions constantly test the performance of boring machines. This open-type TBM, with an excavation diameter of 6.53 meters, a total length of about 250 meters and a weight of about 1,350 tons, had already completed 2,000 meters of trial boring. At the critical juncture of continuing forward, could it overcome the difficulties? This gripped the hearts of the builders.

“Product boring never stops, and service never stops.” Seeing the anxious eyes of their comrades from the client China Railway 18th Bureau Group, CRCHI's on-site technical service personnel “urgently addressed the client's urgent needs and thought about what the client was thinking.” They immediately threw themselves into the repair battle, analyzing the causes and seeking countermeasures, and requested several hydraulic and electrical engineers from nearby construction sites to rush to the rescue overnight. At around 5 a.m. the next day, after the technical elites met up, they surveyed the site and analyzed the situation while reporting the on-site conditions to the group headquarters. Finally, they decided to activate the “electro-hydraulic hybrid power escape mode” specially customized for the project's special geology. After six hours of continuous fighting, the machine was successfully freed! As the cutterhead rotated slowly and steadily, muck was continuously and smoothly carried out by the belt conveyor, rounds of applause broke out in the main control room, and the comrades from the client China Railway 18th Bureau Group gave a thumbs-up.

Here comes the highlight. What is the “electro-hydraulic hybrid power escape mode”? According to Xu Zhen, a technician at CRCHI, conventional TBM cutterhead drive systems mainly include two modes: hydraulic drive and motor drive, each with its own merits. Hydraulic drive has high output torque per unit volume but low efficiency, while motor drive has low output torque per unit volume but high efficiency.

Preparedness averts peril. In response to the requirements for adaptability to construction geology, CRCHI has always focused on non-standard, personalized and customized R&D innovation, thereby driving changes in construction methods. Through long-term research, it successfully developed a TBM equipped with both drive modes. During normal boring, motor drive is used; when short-term high torque is needed, hydraulic motors and electric motors are used in combined drive, greatly improving work efficiency and increasing escape capability by more than 30% compared with conventional TBMs. Especially under harsh and special geological conditions such as rockbursts, collapses and large burial depths, the “electro-hydraulic hybrid power escape mode” is invincible.

“Thank you to your company's engineers for their hard work, and thank you for your company's new technology,” said the ABH project department of China Railway 18th Bureau Group in a letter of thanks. Previously, they had written several times to praise CRCHI's product performance and technical service.