At 10:15 a.m. on May 7, the Laoyingpan tunnel group on the G7611 Zhaotong (Sichuan-Yunnan border) to Xichang section expressway—China's longest spiral tunnel—was fully holed through, with a total of 1,155 days elapsed since construction began.

The Xizhao Expressway, invested and built by China Railway and China Railway City Investment Group, connects Zhaotong City in Yunnan Province and Xichang City in Sichuan Province. The route has a total length of 184.8 kilometers (including 16.7 kilometers of shared alignment with the Yanjiang Expressway and 168.1 kilometers of newly built road), and the entire line is built to a four-lane expressway standard with a design speed of 80 kilometers per hour.

Han Yongjun, project manager of the China Railway No. 2 Engineering Group's Xizhao Expressway project department, which undertook the construction task, told reporters that the Laoyingpan tunnel group is located in the Hengduan Mountain system of southwestern Sichuan. The route passes through mountainous and hilly terrain with steep topography and numerous gorges. The tunnel portals are situated on cliffs, where collapses, landslides and debris flows are prone to occur, posing high safety risks. The tunnels pass through complex geological conditions and phyllite strata with extremely fractured rock; under high overburden conditions, the initial support is prone to deformation and cracking. The tunnels also face various adverse geological conditions such as karst, faults, mud bursts, water inflow, rockbursts and large deformation, making construction highly difficult.

The project department established a scientific research task group and adopted construction methods such as back-pressure soil backfilling for tunnel entry using steel pipe pile retaining walls, short-traverse side azimuth transfer surveying technology, dynamic design of surrounding rock and support parameters, and research on large deformation of phyllite soft rock, ensuring tunnel construction safety.