Construction Plan for the Kongque Mountain Tunnel Project on the Yongzhi–Shanda Highway from Deqin County to Gongshan County

I. Construction Location

The Kongque Mountain Tunnel Project on the Yongzhi–Shanda Highway from Deqin County to Gongshan County is located within Yunling Township of Deqin County and Pengdang Township of Gongshan County. The project starts at K33+768 of the Degong Highway, with the alignment running upstream along the Yongna Creek in an east-to-west direction. A 2,892 m long tunnel crosses Kongque Mountain between K1+620 and K4+512, and the route connects to K57+035 of the Degong Highway at K5+280. The total route length is 5.280 km, with the K0+000–K3+127 section in Deqin County and the K3+127–K5+280 section in Gongshan County. Compared with the old section of the Degong Highway, the total route length is shortened by 17.987 km.

II. Route Alignment

Alignment K begins at K0+000, starting from K33+768 of the Degong Highway. The alignment runs upstream along the Yongna Creek in an east-to-west direction. A 2,892 m long tunnel crosses Kongque Mountain between K1+620 and K4+512, and the route connects to K57+035 of the Degong Highway at K5+280. The total route length is 5.280 km, of which 3.127 km lies within Deqin and 2.153 km within Gongshan. Compared with the old section of the Degong Highway, the total route length is shortened by 17.987 km.

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Main control points: route start at K33+768 of the Degong Highway (elevation 3361 m), Kongque Mountain Tunnel portal at K1+620 (elevation 3413.23 m), Kongque Mountain Tunnel exit at K4+512 (elevation 3341.38 m), and route end at K57+035 of the Degong Highway (elevation 3292.602 m).

III. Construction Content and Scale

The K0+000–K1+465 and K5+100–K5+280 sections will be reconstructed and expanded along the Degong Highway, while the remaining sections will be newly built. The reconstructed and expanded section is 1.645 km long, and the newly built section is 3.635 km long (including 2.892 km of new tunnel and 0.743 km of new subgrade). The project is built to Class II highway standards, with a design speed of 40 km/h and a subgrade width of 8.5 m (10 m for the tunnel section). The pavement is asphalt concrete.

The project includes a total of 106 m/2 bridges, comprising 76 m/1 medium bridge and 30 m/1 small bridge, as well as 6 culverts; 1 long tunnel/2,892 m; 2 at-grade intersections, 1 tunnel management office, and 2 viewing platforms.

IV. Subgrade Cross-Section

Based on the road network function, traffic volume, terrain and geology along the route, the subgrade width for the tunnel section of this project is 10 m, and the subgrade width for the connecting lines at both ends of the tunnel is 8.5 m.

Cross-section layout for the 8.5 m subgrade: 0.75 m (earth shoulder) + 2×3.50 m (traffic lanes) + 0.75 m (earth shoulder).

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