On August 29, the 1st Large‑Diameter Shield Summit opened in Ningbo under the theme “Green Intelligence, Innovation & Collaboration, Leading High‑Quality Development of Large‑Diameter Shield Tunneling”. Altogether 19 authoritative experts including Academician Qian Qihu, recipient of the State Pre‑eminent Science and Technology Award and Professor of Army Engineering University, together with more than 800 scholars and enterprise representatives from universities, research institutes, design‑construction institutes and equipment‑manufacturing sectors across the full industrial chain gathered to conduct in‑depth discussions on large‑diameter shield technical innovation and industrial‑chain collaborative development. Jin Wenge, Deputy General Manager of Luoyang Jiujiu Technology Co., Ltd., headed the company’s delegation, with Gao Honghui from the Technical Department, Li Shupeng and Li Haoyu from the Sales Department present at this major industry event.

At the summit, the Large‑Diameter Shield Green & Intelligent Construction Innovation Platform, co‑initiated by 20 institutions including Southwest Jiaotong University, China Railway 14th Bureau Group and China Railway Fourth Survey and Design Institute Group, and jointly built by 72 participating entities, was officially inaugurated. Eight major scientific and technological achievements in tunnel construction were released on‑site. During the summit, participating experts and representatives conducted field investigations at the Jintang Subsea Tunnel project of Ningbo‑Zhoushan Railway.

As the key controlling project of Ningbo‑Zhoushan Railway, Jintang Subsea Tunnel is currently the world’s longest subsea high‑speed railway tunnel, with a total length of 16.18 km and a shield‑driven section of 11.21 km. Two super‑large‑diameter shield machines of 14.57 m excavation diameter adopted for face‑to‑face tunneling are confronted with world‑class technical challenges summarized as “Four Highs, Three Majors and Two Complexities”:

1. Four Highs: tunneling through weakly weathered tuff with compressive strength up to 200 MPa; construction under 0.85 MPa high water pressure; subsea high‑precision docking with radial misalignment limited within 20 mm; high‑risk in‑tunnel disassembly of shield machines under 21.2 m water depth.
2. Three Majors: large excavation diameter of shield machines; extreme difficulty for subsea docking operations; highly variable strata with drastic lithological differences along the tunnel alignment.
3. Two Complexities: complex adverse geological conditions with 9 faults, 6 joint intensive zones and 1 structural influence zone within the tunnel corridor; complex subsea landforms widely distributed with tidal ridges, troughs and submerged shoals subject to frequent erosion‑deposition, which greatly raise construction risks.

Committed to serving the national strategy of building a powerful transportation country, the company set up a cross‑functional special task force composed of technical, sales and after‑sales personnel to cope with the extremely harsh subsea tunneling conditions of this project. Drawing on its core technical strengths in rock‑breaking cutter development, the team comprehensively analyzed geological survey data, collected and interpreted field tunneling measurement data, and established a closed‑loop response mechanism for on‑site construction feedback. Customized structural design and multi‑round process iteration optimization were carried out for disc cutters, and an integrated disc‑cutter solution matching the complex strata of the project was formulated. Through multiple rounds of on‑site trial‑cutting comparison and testing, our disc cutters delivered outstanding comprehensive performance among products submitted by multiple suppliers. The products were finally selected for project procurement and highly recognized by the construction contractor.

The successful convening of the 1st Large‑Diameter Shield Summit effectively promotes collaborative innovation across the domestic large‑diameter‑shield full industrial chain and accelerates the independent controllability of key underground‑project equipment and core technologies. Taking this summit as an opportunity, Luoyang Jiujiu Technology will continuously tackle key core technologies for rock‑breaking cutters, advance equipment upgrading and transformation of engineering‑oriented technical achievements. It will deploy highly reliable tunneling cutters to support major national underground infrastructure projects, facilitate green and intelligent large‑diameter shield construction, and contribute proprietary technical strength toward building a powerful transportation country.