On June 6th, China Pingjiang Pumped Storage Power Station’s first inclined diversion shaft was fully completed, marking a significant technological milestone for the CRCHI (China Railway Construction Heavy Industry Co. Ltd.) “Tianyue” TBM. The machine, CRCHI claim, is the world’s first steep-inclination, large-and-adjustable-diameter hard rock TBM for use in inclined shafts, having completed a 50-degree slope whilst adjusting its excavation diameter from 6.5m to 8m.
The “Tianyue” TBM, with a total length of 87m and a weight exceeding 900 tons, is composed of over 10,000 parts. It operates on a 50-degree incline, moving upwards whilst simultaneously achieving full-section excavation and primary support in one go on this two-level water diversion inclined shaft. Its tunnelling speed is three times faster than conventional methods, says CRCHI.
The No. 1 diversion inclined shaft spans 1,337.9m. Its “wider-top, narrower-bottom” design features an 8m diameter upper section designed to reduce flow velocity and prevent damage under low-pressure conditions, and a 6.5m lower section that reduced the need for steel usage in the high-pressure zone by over 30%, whilst also reducing deep-large-chamber excavation risks.
“The TBM’s completed the 50-degree slope using three sets of grippers anchored to the shaft wall to form an “anti-slip triangular matrix”. During boring, the mid/rear grippers provide counter-thrust while alternating and re-gripping every 1.5m. This interlocked mechanism ensures a stable ascent, slashing construction time and enhancing safety,” CRCHI says in a statement.
“The “Tianyue” TBM also introduced the conversion of an ultra-large range of excavation diameters from 6.5m to 8m. From the beginning of its development, the research and development team considered the excavation capabilities and structural design for two large spans with different diameters. They achieved the first breakthrough in convertible cutting wheel edge design and expandable shield technology, complemented by a machine host lifting and diameter-changing device. The entire diameter-changing process is safe and efficient, allowing a single set of equipment to tunnel different diameters, significantly reducing costs. This is akin to equipping the TBM with extendable skeletal structure.”
“The successful application of the “Tianyue” TBM has further enhanced the excavation quality and craftsmanship of the water diversion inclined shaft at the Pingjiang Pumped Storage Power Station. It has improved the construction environment and accumulated valuable experience for the mechanized construction of pumped storage power stations,” the statement concludes.
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