Twin bores of Ningqiao Tunnel on Yibin–Panzhihua motorway break through

According to the State-owned Assets Supervision and Administration Commission of Sichuan Province, published on 6 November 2026, the Ningqiao Tunnel, a critical structure on the Jinyang–Ningnan stretch of the G4216 Yibin–Panzhihua Expressway, achieved full breakthrough on 3 November. The cross-border tunnel spanning the Sichuan–Yunnan border took six years to complete and unlocks a key milestone for the whole section.

The tunnel sits in Ningnan County, Liangshan Yi Autonomous Prefecture. It is a twin-bore, two-way mountain tunnel running alongside the valley, with the left tunnel measuring 9,069 metres and the right tunnel 9,103 metres. Its maximum overburden reaches roughly 658 metres, and it is the first long mountain highway tunnel across the country built with a concave longitudinal gradient along its full alignment.

The tunnel portal connects to the Qiluogou interchange, while its exit links directly to the Sichuan–Yunnan Jinsha River Grand Bridge. A vertical difference of around 26 metres separates the two ends. Constraints from local geology, bridge–tunnel connections and the tunnel anchorage of the Jinsha River crossing prompted the custom concave profile. The approximately 9.1-kilometre alignment falls first and then rises, absorbing the height difference within the tunnel envelope. The design satisfies the fixed gradient requirement for direct access onto the bridge and allows a combined ventilation and drainage adit to be positioned at the lowest point of the bore.

The tunnel exit passes close beneath the anchorage block of the Jinsha River Grand Bridge, which has a main span of 1,060 metres. At its thinnest point, only about 17 metres of rock separates the tunnel crown from the base of the anchorage. Controlled micro-seismic blasting was deployed for this section, with monitoring stations collecting real-time readings so excavation parameters could be adjusted dynamically to preserve structural safety while maintaining advance rates.

Around 60 kilometres of the Jinyang–Ningnan section are already finished, and work continues steadily on other major works including the Ningnan Tunnel. Once opened, the stretch will mark the arrival of the first motorway access for Butuo and Jinyang counties. Journey times between Jinyang and Ningnan will fall from three and a half hours to one and a half hours.

The Yibin–Panzhihua Expressway is invested and constructed by Shudao Group. It ranks as the single largest highway investment project in China and carries the longest route within Sichuan. The full 446-kilometre route is split into three segments, built as a dual two-lane carriageway with a design speed of 80 kilometres per hour. The completed route will cut the drive from Yibin to Panzhihua from roughly ten hours to six hours, forming a new major corridor out of Sichuan towards Yunnan.