Entering into the New Zealand and Australian scene, CRCHI is unveiling its triple-circular pipe roofing machine which has already had major success throughout Asia.
The Triple-Circular Pipe Roofing Machine, named “Lucheng”, represents a new species of trenchless tunnelling equipment and rolled off the production line in July 2025 at the No. 3 Industrial Park of CRCHI Changsha.
The tunnel for the Sanya Estuary Passage Project, a critical undersea link connecting Sanya Central Business District (CBD) and the Phoenix Coast Unit, has a total length of 127m. Construction involves 28 pipe roofing structures, with a cumulative excavation length of more than 1km. The alignment passes through silty clay, gravelly sand, clay, fault breccia, and moderately weathered quartz sandstone. The strata are characterised by a soft-over-hard and hard-then-soft distribution, with pronounced heterogeneity. Such ground conditions impose high requirements on the rock-breaking capacity and impact resistance of the tunnelling equipment. At the same time, multiple slurry circulation systems need to be specifically designed to mitigate the risk of collapse in soft-over-hard strata. To overcome these challenges, in collaboration with the client, CRCHI developed an innovative construction method: a pilot pipe combined with a Triple-Circular Pipe Roofing Machine.
The single circular pipe-roof machine was used to complete four independent pipes and eight pilot pipes. The lateral pipe-roof machines undertook eight sets of combined pipe roofs. This approach significantly enhanced construction efficiency compared with conventional single-face pipe-roofing machines, which could not have met the stringent schedule requirements.
The proposed Combined Pipe Roofing Construction Method is a tunnelling technique that utilises an interlocking arrangement of circular pipe roofs to achieve the simultaneous excavation and support of the surrounding ground. This method consists of two main stages: installation of the central pilot pipe roof and subsequent construction of the lateral pipe roofs.
In the first stage, the pilot pipe roof is excavated and jacked forward to form a guiding alignment. Upon completion, the pipe remains embedded in the soil, serving as a navigation and orientation reference for the following jacking operations. In the second stage, the lateral pipe roofs are connected to the pilot pipe at the tunnel face. As jacking progresses, the lateral pipes follow the trajectory of the pilot alignment, ensuring precise positioning and breakthrough. During this process, the pilot pipe is gradually displaced and pushed out by the lateral pipes, allowing it to be recovered, replaced, and reused.
This method provides a reliable means of pre-support and ground stabilisation, enabling safe excavation in complex geological conditions.
The machine, namely “Lucheng”, is a combination of three boring units. The pipe-roof machine in the centre has an excavation diameter of 2.27 m and is interlocked with two lateral pipe-roof machines, each with an excavation diameter of 2.07 m. It will be applied to the tunnel with a cross-section of 18.4 m × 18.4 m and a length of 127 m, will be constructed using 12 pipe roof sections serving as both temporary support and permanent structure. The project features water-saturated strata, primarily traversing quartz sandstone, fault breccia, gravelly sand, and silty clay. With upper soft layers overlying extremely hard rock formations, the project exhibits high compressive strength.
To overcome these engineering challenges, CRCHI developed an innovative “Pilot-Pipe Guided, Lateral Pipe Jacking” design for a Triple-Circular Pipe Roofing Machine. The machine adopts several key customised technologies, including a multi-posture, freely combinable machine, a multi-angle adaptive portal thrust system, a high-precision combined guidance and deviation correction system, and a special-shaped combined portal sealing system. The successful implementation of this project will significantly improve construction efficiency and reduce operational risks.
The development of this equipment, spanning four years from process research to finalisation, has achieved breakthroughs in multiple cutting-edge technologies, filling critical gaps in the industry. Its successful development provides a pioneering “CRCHI solution” for worldwide projects with complex geological conditions and large tunnel-face pipe roofing.
For more information, contact tangzhongwu@crchi.com